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SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 607

Zoogeography and Systematics of the Lanternfishes of the Genus Nannobrachium (Myctophidae: Lampanyctini)

Bernard J. Zahuranec

Smithsonian Institution Press

Washington, D.C.

2000

ABSTRACT

Zahuranec, Bernard J. Zoogeography and Systematics of the Lanternfishes of the Genus Nannobrachium (Myctophidae: Lampanyctini). Smithsonian Contributions to Zoology, number 607, 69 pages, 25 figures, 34 tables, 2000. Of those lanternfishes in the genus Lampanyctus (sensu lato) with short or no pectoral fins, 17 species are recognized, removed to the separate genus Nannobrachium, and placed into five species groups. These groups are designated Nigrum (four species), Regale (five species), Cuprarium (two species), Achirus (five species), and Isaacsi (one species).

The genus Nannobrachium includes those species of the tribe Lampanyctini that are characterized by the following features: either a lack of pectoral fins or short fins with a narrow base in adults; vertically elongate, squarish otoliths with smooth margins; reduced musculature resulting in a soft, flaccid body; body profile appearing “pinched” with concave dorsal and ventral profiles behind the head; and swimbladder atrophied in adults.

The four species in the Nigrum group are N. nigrum, from the tropical and subtropical Pacific and eastern Indian oceans; N. atrum, from the temperate North and South Atlantic, South Indian, and Southwest Pacific oceans; N. gibbsi, herein described from the tropical Pacific; and N. indicum, herein described from the tropical Indian Ocean. All have extremely reduced pectoral fins with downward pointing fin rays in the adult.

All five species in the Regale group are confined to the Pacific Ocean: N. regale in the Subarctic and North Temperate; N. ritteri in the eastern North Pacific Subarctic and Temperate; N. fernae in the eastern North Pacific Temperate; N. idostigma in the eastern tropical Pacific; and N. bristori herein described from the North Subtropical Pacific. In the Regale group, the pectoral fin is not as reduced compared with other Nannobrachium groups, and the VLO photophore is low on the side of the body.

The two species in the Cuprarium group are N. cuprarium, bipolar in the subtropical Atlantic, and N. lineatum, from the tropical-subtropical Atlantic, Indian, and Pacific oceans. Both species have black pigmentation on the posterior of the supracaudal and infracaudal luminous glands.

Four of the five species in the Achirus group are herein described: N. hawaiiensis, N. crypticum, and N. phyllisae from the North Central, Equatorial, and Southeast Pacific, respectively; and N. wisneri, circumglobal from the southern temperate and subtropical regions. The previously described N. achirus is circumglobal in the Subantarctic. In all five species, the pectoral fin becomes greatly reduced or is completely lost and covered over by skin in adults.

The Isaacsi group contains only N. isaacsi from the eastern tropical Atlantic. It has the VO₂ photophore raised in position, above and slightly forward of the VO₁.

Most of the species and species groups show remarkably little overlap in their distributions. Analysis of the distribution patterns revealed distinct patterns concordant, or largely so, with patterns recognized for other oceanic organisms.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Annals of the Smithsonian Institution. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus).

Library of Congress Cataloging-in-Publication Data

Zahuranec, Bernard J.

Zoogeography and systematics of the lanternfishes of the genus Nannobrachium (Myctophidae: Lampanyctini)/Bernard J. Zahuranec

p. cm—(Smithsonian contributions to zoology ; no. 607)

Includes bibliographical references (p. )

1. Nannobrachium. I. Title. II. Series.

QL1.S54 no. 607 [QL638.M9] 590 s–dc21 [597′.61]

00-029136

art The paper used in this publication meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library Materials Z39.48—1984.

Zoogeography and Systematics of the Lanternfishes of the Genus Nannobrachium (Myctophidae: Lampanyctini)

Bernard J. Zahuranec

____________

Bernard J. Zahuranec, Office of Naval Research, International Field Office, 800 North Quincy St., Arlington, Virginia, 22217.

Review Chairman: Richard P. Vari, Department of Vertebrate Zoology, Smithsonian Institution, Washington, D.C. 20560-0159.

Reviewers: John Paxton, Australian National Museum, Sydney; Robert Karl Johnson, Grice Marine Laboratory, University of Charleston, Charleston, South Carolina, 29412. P. Alexander Hulley, South African Museum, Cape Town 8000, South Africa.

Introduction

Among the open-ocean midwater fishes, the lanternfishes (family Myctophidae) are notably common and numerous both in terms of species and individuals (Hulley, 1995). Of the many genera in the family Myctophidae, the genus Diaphus contains the greatest number of species, whereas the genus Lampanyctus (sensu lato) is probably the most widespread and second in number of species (Backus et al., 1977).

Lampanyctus was erected by Bonaparte (1840), with Gasteropelecus crocodilus Risso (1810) the type-species by monotypy. As Moser and Ahlstrom (1974) pointed out, it has been a catchall taxon ever since, even in Fraser-Brunner's (1949) and Paxton's (1972) reviews of the family. Since Fraser-Brunner's review, however, a number of species have been removed from Lampanyctus or described in separate genera. Several of these (Stenobrachius, Triphoturus, and Lepidophanes) were recognized as subgenera by Fraser-Brunner (1949) and were elevated to generic status by Bolin (1959). Hubbs and Wisner (1964) erected the genus Parvilux for two new species from the northeastern Pacific, and Paxton (1972) erected the genus Bolinichthys for several species in Fraser-Brunner's subgenus Lepidophanes.

Within the narrowly defined Lampanyctus, Paxton (1972), essentially following Bolin (1959), recognized three groups: those with moderate to long pectoral fins and with cheek photophores, to which the name Lampanyctus applies; those with long pectoral fins but lacking cheek photophores, for which no generic or subgeneric name has been proposed; and those with short or no pectoral fins and no cheek photophores, to which the name Nannobrachium applies. Although it was beyond the scope of his study to examine all species of Lampanyctus, Paxton (1972) did compare material of several species from each group; however, he thought that recognition of these three groups as subgenera necessitated a more thorough investigation of the species involved.

The species of the genus Lampanyctus have frequently caused taxonomic problems, with the species of the short-pectoral-finned group especially difficult to distinguish and identify. Robert H. Gibbs, Jr., in his capacity as the co-advisor for my doctoral dissertation, informed me (pers. comm., 1973) that numerous taxonomists have expressed reservations about the validity of many of the short-pectoral-finned species. There are several reasons for this confusion. In the first place, the fish are particularly fragile and are easily damaged in collecting nets, so most specimens are in poor condition. Second, the group contains many morphologically similar species from many parts of the world's oceans. Third, although there is limited variability in most characters, there is enough variability in some cases for similar species to overlap, even in those characters wherein they differ most significantly. The problems have been compounded because specimens of many of the species were rare until the buildup of modern oceanographic collections.

The short-pectoral-finned group is defined and recognized herein as a monophyletic assemblage, the genus Nannobrachium. By amassing a large amount of comparative material from all over the world, those characters found useful for separating the species and for assessing their variability have been evaluated. A total of 17 species in five species groups are recognized and are defined herein, whereas 10 species were recognized previously, and their distributions are described and compared. Definitive corroboration of the monophyletic status of the five species groups of Nannobrachium, however, awaits further study with additional material.

ACKNOWLEDGMENTS

It is with great pleasure that I thank a wide variety of people for their help in producing the doctoral dissertation that was the forerunner of this paper. First of all, my late thesis advisor, Robert H. Gibbs, Jr., was of great assistance throughout. Robert L. Wisner also helped with practical ideas on many occasions as did Basil Nafpaktitis and William Aron. Robert Lavenberg, Los Angeles County Museum (LACM) of Natural History, loaned material and also helped check specific points concerning the osteology of a number of myctophids that had been studied by John Paxton. Many other people, too numerous to mention, provided material on loan.

A number of people have read parts or all of the manuscript and have provided constructive criticism. Richard H. Backus, Woods Hole Oceanographic Institution, was especially helpful. In particular, he and his associate, James E. Craddock, made useful suggestions during discussions concerning zoogeography. In San Diego, the late Elbert H. Ahlstrom, H. Geoffrey Moser, Richard H. Rosenblatt, and Robert L. Wisner read and discussed with me various parts of the manuscript. P. Alexander Hulley of the South African Museum made suggestions concerning the identification keys, provided some of his own unpublished data on these fishes, and reviewed the manuscript. John R. Paxton of the Australian Museum, Sydney, reviewed the manuscript and made valuable suggestions.

At the Smithsonian Institution, many people helped in many ways: Charles Roberts with statistics, David Dance and Kenneth McCormick with computer expertise, Lee Ann Hayek with the principal components analysis, Kurt Bruwelheide and Diane Bohmhauer Tyler with a variety of miscellaneous tasks, as well as Edgar N. Gramlin and Susan Jewett. I am especially indebted to Richard Vari and Joseph Russo for their assistance and encouragement.

Special thanks to Deborah Bowman Cox, Donna Dennison, Denise Peterson, and Bobi Randall for help with typing the manuscripts and tables. Due to changeover between incompatible word processing systems, the manuscript had to be put back into working condition again. This was smoothly done, thanks to Jacqueline Myles’ dedicated assistance. The fish drawings were done by Brian Stone, South Carolina Department of Natural Resources, Charleston. Thanks are due to Lawrence Behunek and Jennifer Rielly, Office of Naval Research, for final preparation of the illustrations. Finally, for an enormous amount of patient help, thanks to my wife Jean and to Robert K. Johnson, University of Charleston, who went far beyond what a friend might be expected to do in encouragement and in helping me prepare the manuscript for publication.

MATERIALS AND METHODS

More than 9000 specimens were examined in the course of this study. A complete listing of material examined is available upon request from the Division of Fishes, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, or from the Grice Marine Laboratory (Attention: Dr. Robert K. Johnson), University of Charleston, Charleston, SC 29412. Institutional acronyms cited in the present paper are as listed in Leviton et al. (1985), except as follows: IOM is used for the Institute of Oceanology, Academy of Sciences, Moscow, instead of IOAN; HIMB is used for the Hawaiian Institute of Marine Biology, University of Hawaii; MLML is used for the Moss Landing Marine Laboratory, Moss Landing, California; NMFS is used for the Fishery Oceanography Center, National Marine Fisheries Service, La Jolla, California; NZ is used for the New Zealand Fisheries Research Division, Wellington, New Zealand; ORSTOM is used for the Office de la Recherche Scientifique et Technique Outre-Mer, New Caledonia; UCSB is used for the University of California, Santa Barbara, California; and OS is used for the Department of Oceanography, Oregon State University.

Traditionally, various investigators, including Günther (1887), Gilbert (1891, 1906, 1915), Tåning (1928), and Fraser-Brunner (1949), classified the species in the family Myctophidae by using differences in the position and numbers of photophores. Although photophore differences are still of primary importance, increased emphasis is herein placed on other taxonomic characters, including morphometry.

Except as noted, meristic methodology follows Hubbs and Lagler (1958), and photophore nomenclature follows Wisner (1976) and Nafpaktitis et al. (1977) (Figure 1). All dorsal- and anal-fin rays were enumerated, including any of the anteriormost tiny rays that may be buried in the skin at the origin of the fin. This differs from the technique of Wisner (1976) and Bolin (fide Wisner, pers. comm., 1975), where the first, weak halfray, when present, was ignored. It proved extremely difficult to decide when a first ray was so small and weak that it should be ignored rather than counted as one of the ordinary shorter rays that precede the longest robust rays. Thus, all rays that could be seen and had separate bases at the body surface were counted. The last rays are commonly split almost to the base and were counted as one.

In comparing the positional differences of photophores, they have usually been related to other photophores, instead of relating them to other anatomical structures. This is at variance with methodologies of more recent investigators (Nafpaktitis and Nafpaktitis, 1969; Wisner, 1976) but was found to be a more useful technique. Descriptions of the photophore patterns given for each species are for the typical or commonest pattern. Atypical photophore arrangements are discussed in the sections on geographic variation.

In Lampanyctus the last AOa photophore is clearly raised above the level of the rest of the AO series and is considered to be the first of two Pol photophores, not part of the AO series; however, any reference to the position of the Pol in these fishes refers to the second or upper Pol, consistent with common usage. The infracaudal and supracaudal luminous structures are called glands following Wisner (1976) and Nafpaktitis et al. (1977). The structures making up the glands resemble scales and are referred to as such, following those authors. All developed gill rakers on the first arch were counted, with the central raker at the angle included in the lower-limb count.

FIGURE 1.—Idealized Nannobrachium cuprarium (adapted from sketch of lectotype by Nafpaktitis, 1973, fig. 39) showing nomenclature of photophores, enlargement of black pigment cap on supracaudal gland, and technique used to measure adipose-fin length.

The number of tooth patches on the lower limb of the second gill arch was found to be an extremely useful diagnostic character. The second gill arch typically has three or four tooth patches, plus one gill raker on the upper limb, one gill raker at the angle, and one gill raker plus 8 to 12 tooth patches on the lower limb. In a few specimens, the posteriormost tooth patch on the lower limb may be developed into a second gill raker; however, this usually does not change the total number of elements from the typical number for the species. Consequently, counts of the tooth patches on the lower limb of the second arch that are given for each species are typical counts, even though a few specimens of virtually all species have one fewer tooth patch but two gill rakers on that lower limb. In order to determine whether the anteriormost tooth patch should be counted or not, the gill arch was lifted and rocked back and forth. If the tooth patch moved with the gill arch, it was counted, but if the tooth patch was forward of the hinge joint and, therefore, did not move with the gill arch, it was not counted. Occasionally, a tooth patch clearly was on the hinge but did not move when the gill arch was rotated. In that case, it was counted as art of a tooth patch. This occurred infrequently and made little difference for identifying specimens.

Except as noted, all measurements were taken following the techniques of Hubbs and Lagler (1958), using needle-point dividers and a binocular dissecting microscope. Using a steel rule, the measurements were estimated to the nearest 0.2 millimeters. Specimen length was measured as standard length (SL). Post-adipose length was measured from the notch at the posterior base of the adipose fin to the caudal base, following Wisner (1976). This avoided the difficulty of having to select some arbitrary spot on the “ramp” preceding the fin proper as the origin of the adipose fin. On the other hand, in order to measure the length of the adipose fin, the point where the fin itself arises from the “ramp” was taken as the origin of the adipose fin (Figure 1). Thus, the adipose-fin length measurements are probably prone to greater error than most of the other measurements taken on these fish.

Measurements were taken of 20 point-to-point dimensions, including standard length (in mm), for more than 20 specimens of each species. The means, standard deviations, and ranges of these, as thousandths of standard length, were calculated using the Statistical Package for the Social Sciences (SPSS) (Nie et al., 1977) and are given for each species in the measurements tables in the text. These statistics do not take into account any effects of allometry. Information concerning allometry was obtained from individual scatter plots of each measurement versus standard length for that species, and from a REGRESS program that employed a t-test for allometry. Both programs were developed by Richard Goodyear, formerly at the Smithsonian Institution. In the measurements tables, the abbreviations for indicating the significance level of tests of allometry are as follows: Sig (p <0.05), Slt (0.05 < p < 0.10), 0= nonsignificant with + or – indicating positive or negative allometry. In indicating the results of regression analyses, Y denotes the dependent variable (head depth, predorsal depth, etc.), × denotes the independent variable (SL).

Measurement data also were used to obtain an independent, quantitative assessment of assignment of species to the five Nannobrachium species groups that had been based on criteria other than these morphometrics. The 19 measurements treated as fractions of standard length for at least 20 specimens of each species were subjected to a stepwise discriminant analysis (Rao, 1965), using standard techniques (Nie et al., 1977). Stepwise discriminant analysis determines the important variables for deciding assignment of cases (i.e., specimens) to groups (species groups). The similarity of specimens within a group is demonstrated by the production of a plot of the first two discriminant scores on a graph. Although the techniques are similar to a principal components analysis, it is more appropriate to apply these techniques herein because the categories (i.e., species) are assumed to be known and the cases have already been assigned to categories (i.e., specimens measured have been identified to species).

The practical use of the measurement data to aid in the identification of species proved extremely difficult. All species are quite similar morphologically, and most species within the same species group appear virtually identical in shape. Although there are subtle differences between even the most similar appearing species, individual specimens often are damaged and/or preserved in a distorted condition, which masks these differences.

In an attempt to solve this problem and to extract any information present on morphological differences, a number of statistical procedures were used. I visually scanned the data in the tables of measurements for each species and found a series of 76 ratios of various pairs of the measurements that showed promise for significant mensural differences between species as based on t-tests. Next, I used SPSS (Nie et al., 1977) to perform a discriminant function analysis for all possible combinations of pairs of species within each previously determined species group. An index value of discrimination was produced from those five ratios that were found to give the best separation for each pair of species. These index values were plotted for each pair of species, and an average value of group means was obtained, termed herein the Discrimination Value (D.V.). Information obtained from these discriminant function analyses for species pairs is in Appendix tables A12–A14. These can be used to assist in identifying a particularly difficult unknown specimen where using the appropriate identification keys and meristics tables has brought the number of choices to two similar species. Use instructions are with the tables in the Appendix. Text and figure abbreviations are as follows:

A | anal-fin rays
D | dorsal-fin rays
GR | gill rakers (upper limb + lower limb)
LL | lateral line scale pockets or pores (lateral line scales missing in virtually all specimens examined)
P₁ | pectoral fin
P₂ | pelvic fin
SC/IC | supracaudal / infracaudal “gland scale” counts; preceding isolated “luminous scales” are denoted in lower-case Roman numerals (e.g., i=1, ii=2)
Sig | allometry t-test significance level of p <0.05
SL | standard length
Slt | allometry t-test significance level of p >0.05, <0.10
V | vertebrae (precaudal + caudal)

The Genus Nannobrachium

Nannobrachium Günther, 1887:199 [type-species Nannobrachium nigrum Günther, 1887, by monotypy].

Paralampanyctus Kotthaus, 1972a:13 [type-species Lampanyctus niger (Günther, 1887), by original designation].

The species of the tribe Lampanyctini were defined by Paxton (1972) to have the following features: (1) short (never reaching far beyond pelvic-fin base), rudimentary, or no pectoral fins with narrow base always equal to or shorter than distance between lower orbital margin and toothed margin of upper jaw in the adult; (2) solid, squarish otolith, longest vertically, without prominent notch or rostrum, often somewhat rounded into a kidney-bean shape; (3) weak musculature resulting in a soft, flaccid body; (4) body profile appearing “pinched” because both predorsal and preanal profiles tend to be concave, with body depth a short distance anterior to dorsal fin less than at dorsal-fin origin and less than at nape; and (5) swimbladder in adults either greatly reduced or completely lost, but never well developed and filled with gas.

Post (1972) found an “extra” chromosome in members of the “Lampanyctus ater group,” which he thought would help separate that group from the rest of Lampanyctus. The situation appears, however, to be variable because Chen and Ebeling (1974) found that, although L. ritteri also had an atypical karyotype (apparently not an “extra” chromosome), L. regalis had the typical complement of the rest of Lampanyctus. Both species are herein considered to belong to the genus Nannobrachium. Some of the above-listed characters, especially the otolith shape, were utilized by Kotthaus (1972a) to erect the genus Paralampanyctus, which is a junior synonym of Nannobrachium.

The variability of otolith shape was examined to assess the value of this character for defining the genus. Large series of otoliths were available from fresh material in the Ocean Acre collections (Gibbs et al., 1971) of the three North Atlantic species of Nannobrachium: N. atrum, N. cuprarium, and N. lineatum. There is considerable variability in fine detail of otolith shapes (Figure 2) in these three species, but all are generally of similar form. This same squarish, vertically elongate shape is clearly evident in comparative material from four species of Nannobrachium from the Pacific, especially when contrasted with other species of Lampanyctus from the North Atlantic, except L. macdonaldi, which has otoliths similar to Nannobrachium. The otoliths of the two species of Parvilux also are superficially similar, but Fitch (1969) pointed out that the otoliths of Parvilux are slightly concave rather than straight as in Nannobrachium.

FIGURE 2.—Lateral view of otoliths (sagittae): a, Nannobrachium atrum, Ocean Acre, USNM; b, N. cuprarium, Ocean Acre, USNM; c, N. gibbsi, Eltanin Cruise 31, sta 13A, USNM; d, N. nigrum, Eltanin Cruise 31, sta 11A, USNM; e, N. lineatum, Ocean Acre, USNM; f, Lampanyctus crocodilus, MCZ RHB 1248; g, L. festivus, MCZ RHB 1128; h, L. photonotus, MCZ RHB 1149; i, L. nobilis, MCZ RHB 1415.

TABLE 1.—Diagnostic characters of species groups of Nannobrachium.

Nannobrachium can be distinguished from all other genera in the Myctophidae, except Triphoturus and Parvilux, by the combination of characters listed above. Nannobrachium shares with those two genera and with the Macdonaldi species group of Lampanyctus the features of short pectoral fins and weak musculature resulting in a soft, flaccid body. In common with Triphoturus and Parvilux, Nannobrachium has a “pinched” body profile and narrow pectoral-fin base, whereas it shares a squarish, vertically elongate otolith and an atrophied swimbladder in adults with Parvilux and the Macdonaldi group.

Complete descriptions of larvae of Nannobrachium species have been published only for N. bristori, N. hawaiiensis, N. idostigma, N. regale, N. ritteri (Moser and Ahlstrom, 1996), and possibly N. achirus (see Moser and Ahlstrom, 1974). Larvae of Nannobrachium species share some common characteristics that may prove characteristic of the genus as a whole when the larvae of other species are known. Larvae are robust and have large heads with a more or less pointed snout. The pectoral fins are relatively large in most species of Nannobrachium, and they are very large and fan-shaped in some others (e.g., N. hawaiiensis). The large jaws have strong teeth and a tooth patch at the tip of the upper jaw. The tooth patch is borne on paired elements that are produced into a beak-like structure in some species (e.g., N. achirus).

Because there has been so much confusion regarding the identification of these species, it was not always possible to determine whether species in the literature were correctly identified without an examination of the material in question. Where literature references could be determined with some likelihood or certainty based on description, locality data, or other information, the citation was listed but was noted as questionable (i.e., with “?”) or “in part” as explained below. In the species synonymies, known partial misidentifications by a given author are indicated by “in part,” and, where necessary, by question marks as follows: [?in part]—identification probably at least partly correct but unconfirmed; [in part?]—identification known to be at least partly correct (some specimens), but the series of specimens reported also likely contained (unconfirmed) one or more additional species; [?in part?]—a combination of both uncertainties. The following references could not be confirmed, and the identifications must be considered uncertain.

Lampanyctus achirus.—Bekker, 1967b:179.

Lampanyctus ater.—Fraser-Brunner, 1931:224.—Belyanina, 1981:78–79.

Lampanyctus idostigma.—Stiassny, 1996:426.

Lampanyctus lineatus.—Parin, 1976:199.

Lampanyctus niger.—Gilbert, 1913:100.—Fowler, 1928:68; 1936:382, 391–392.—Borodin, 1931:76–77.—Kulikova, 1960:29–33.—Bekker 1967b:179. Bradbury et al., 1971:434.—Parin, 1971:82; 1975:321; 1976:199.—Borodulina, 1972:696, 698, 700, 701.—Parin et al., 1973:114–115.—Clarke and Wagner, 1976:642.—Willis et al., 1988:87.

Lampanyctus niger species group/complex.—Clarke, 1982:299, 303.

Lampanyctus nigrum.—Stiassny 1996:426.

Lampanyctus regale.—Stiassny, 1996:426.

Lampanyctus regalis.—King and Iversen, 1962:320.

Lampanyctus ritteri.—King and Iversen, 1962:320.—Parin et al., 1973:115.—Beebe and Vander Pyle, 1944:86–87.

Macrostoma nigrum.—Fowler, 1936:1231.

Myctophum (Lampanyctus) nigrum.—Pappenheim, 1914:199.—Barnard, 1925:239.

Myctophum nigrum.—Herre, 1953:144.

The Species Groups of Nannobrachium

Five species groups are recognized in Nannobrachium as a result of this study. These are not proposed as formal taxa but are phenetic groups named after the oldest described species in each group: the Nigrum, Regale, Cuprarium, Achirus, and Isaacsi species groups.

FIGURE 3.—Artist's rendering of plot of first two discriminant scores of selected proportional measurements for all species of Nannobrachium (see “Methods” for explanation). The species clusters are denoted by the solid thin lines. Envelopes for all species groups are denoted by separately labeled bold solid and dashed curves.

All species in each group share at least one distinguishing character unique to that group among the species of Nannobrachium. In addition, all species in each group share a suite of one or more characters that are not unique to that group (also being found in other species of Nannobrachium). Thus, although some characters making up this suite are shared with species in other groups, the entire suite of characters is unique to that group. The characters for each group are discussed in the sections preceding the species accounts and are given in Table 1.

Recognition of five species groups is based on differences and similarities in photophore positions, condition of pectoral fins, and (one case) pigmentation. The groups have been corroborated by a step-wise discriminant analysis (Rao, 1965) of morphometric data. In this analysis, the most important variable for discriminating among species was length of the solid infracaudal gland; the second most important was caudal-peduncle depth. That is, these two variables contributed (or explained) the greatest amount of variation between species as expressed by the first discriminant scores. Because of the morphological similarity between species of Nannobrachium a plot of the discriminant scores resulted in a high degree of overlap; therefore, Figure 3 is an artist's rendering using thin solid lines to enclose the cluster of symbols for each species but with the symbols deleted. Thicker curves enclosing all species envelopes within each species group clearly show the grouping of the species clusters. Thus, the species groups, originally recognized largely on the basis of photophore arrangement differences, are independently supported by these clustering techniques using only morphometry. It is clear from the amount of overlap, however, that morphometry alone cannot be used to separate species or species groups.

Identification of Nannobrachium Species

To facilitate the identification of material, keys have been constructed. The first includes all species and species groups in a “natural” system, using those characters by which the species groups may be distinguished.

Because these species are so similar to each other, they are frequently difficult to identify properly. Knowing the geographical region from which the specimens were obtained can usually simplify the process, especially if the number of possible species in the key has been reduced accordingly. Consequently, an additional set of four keys was constructed for the major ocean areas to include the species of Nannobrachium that occur there.

In addition, where uncertainty exists in the identification of a specimen, perhaps because of its damaged condition, but where it has been identified to one of two possibilities, then the Discrimination Value (D.V.) in the Appendix may help resolve the dichotomy. Alternatively, Tables A2–A8, giving meristics obtained in this study, may help with identifications. Finally, it must be borne in mind that there are probably a number of undescribed species of Nannobrachium in the world's oceans. Specimens of undescribed species may be expected, particularly from the southern hemisphere, and especially from the Indo-Pacific region. In this regard, however, it is worth repeating Fraser-Brunner's (1949:1082) admonition (for Lampanyctus sensu lato but which holds especially for Nannobrachium) that “under no circumstances should a doubtful specimen of this genus be described as a new species unless adequate comparative material is available.”

Key to Species Groups and Species of Nannobrachium

Key to the Species of Nannobrachium in the Atlantic Ocean

Key to the Species of Nannobrachium in the Indian Ocean

Key to the Species of Nannobrachium in the North Pacific Ocean

Key to the Species of Nannobrachium in the South Pacific Ocean

The Nigrum Group

This group is distinguished by the extremely reduced pectoral fin. The pectoral fins of adults are more weakly developed and have thinner rays than in any other group. The fin length is less than one-half the distance to the pelvic-fin insertion, and the rays are extremely fine and flexible. In contrast, the species in other groups either lack pectoral fins or, if present, the fins are either longer than one-half the distance to the pelvic-fin insertion or they are shorter but have thick and stiff rays. In addition, in large adults of the Nigrum group, there is a pronounced tendency for the pectoral fins to point downward.

Other characters shared by all species in the Nigrum group are as follows: (1) VLO close to, or touching, the lateral line; always less than 2 photophore diameters below the lateral line and closer to the lateral line than the PLO is to the lateral line; (2) SAO₁ above the VO2–3 interspace; (3) Prc₃ directly under Prc₄, usually closer to Prc₂ than to Prc4; (4) Pol₂ under the adipose fin or on a vertical from its origin. These and other characters are compared in Table 1 for all the species groups of Nannobrachium.

The Nigrum group contains four species: N. nigrum Günther, 1887; N. atrum (Tåning, 1928); N. gibbsi, new species; and N. indicum, new species. Modal characters of all species in the Nigrum group are listed in Table A1. Characters for N. crypticum, a new species in the Achirus group, and N. bristori, a new species in the Regale group, are included in Table A1 because both species have features that are similar to those of the species in the Nigrum group.

Nannobrachium nigrum Günther, 1887

FIGURE 4, TABLE 2

Nannobrachium nigrum Günther, 1887:199–200, pl. LII, fig. B [original description].—Gilbert, 1905:591 [description, Hawaiian Islands].—Herre, 1953:144 [original description listed].—Paxton, 1979:13 [holotype listed].

Myctophum (Lampanyctus) nigrum.—Brauer, 1906:242–243, 385 [in part] [distribution: Atlantic, Indian, and Pacific oceans].

Lampanyctus niger.—Parr, 1928:87 [key, similarities to L. ater].—Nafpaktitis, 1973:39–40 [figure, comparison with L. ater].—Parin, 1975:321, 325, 326 [?in part?] [tropical Pacific].—Clarke and Wagner, 1976:642 [?in part?] [vertical distribution].—Wisner, 1976:175–176 [description, distribution, figure].—Parin et al., 1977:122, 123, 165, 166 [in part] [western Pacific].—Nafpaktitis et al., 1977:204–206 [discussion, figure of holotype].—Clarke, 1978: 499–502 [feeding patterns]; 1983a:327, 328, 332 [abundance estimates]; 1983b:205–206 [in part?] [sex ratio, size]; 1987:65 [central Pacific biogeography].—Chen, 1983:199 [?in part] [South China Sea] [fide J. Paxton].—Huang and Yang, 1983:234 [?in part] [Dongsha Islands, South China Sea] [fide J. Paxton].—Fujii, 1984:69, pl. 66-M [?in part] [description, distribution].—Cheng and Zheng, 1987, unpaginated [?in part] [China records] [fide J. Paxton].—Kailola, 1987:103 [?in part] [Solomon Sea].—Yang et al., 1996, unpaginated [?in part] [Nansha Islands, northeast South China Sea] [fide J. Paxton].

Lampanyctus (Lampanyctus) niger.—Fraser-Brunner, 1949:1085 [in part] [illustrated key].—Bekker, 1983:87–89, 198–200 [in part] [key, description, distribution].

Paralampanyctus niger.—Kotthaus, 1972a: 14 [designated genotype].

Lampanyctus niger (Form B).—Clarke, 1973:416–418 [ecology north of Hawaii].

FIGURE 4.—Nannobrachium nigrum Gunther, 1887. Drawing of 81.5 mm specimen, USNM 298046, Pacific Ocean, 20° 20′–20° 30′N, 158° 20′–158° 30′W. (Scale bar=1 cm.)

COMPARATIVE DIAGNOSIS.—Nannobrachium nigrum (Figure 4) can be distinguished from the other species of the Nigrum group and from N. crypticum in the Achirus group primarily by its gill-raker count (total 15–18) and number of tooth patches on the lower limb of the second gill arch (9–10) (both higher than in N. gibbsi, N. indicum, and N. crypticum). It can be distinguished from N. atrum by the lower number of AO photophores (10–13), anal-fin rays (14–18), lateral line organs (32–34), and vertebrae (33–37) and by having the SAO series farther back than in N. atrum (Table 3). It can be distinguished from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 31 specimens from the Pacific Ocean and are given in Tables A1–A8.

Proportions: Given in Table 2.

Fins: Origin of anal fin behind vertical from middle of base of dorsal fin. Pectoral fins not reaching beyond vertical from PO₃, with extremely weak and flexible rays. Adipose-fin base above end of anal-fin base, with adipose origin usually only slightly before end of anal-fin base.

Luminous Organs: PLO 1–3 photophore diameters below lateral line. PO₄ slightly higher than level of PVO₂ or on same level and above or slightly behind vertical from PO₃. VLO less than one photophore diameter below, frequently nearly touching, lateral line. SAO₂ closer to AOa₁ than to VO₄ or equidistant from VO₄ and AOa₁. SAO₃ approximately above AOa₁. AOa₁ slightly depressed and AOa1–2 interspace enlarged. AOp₁ at or behind end of anal-fin base. Prc well separated from AOp; Prc1–2 on horizontal line or Prc₂ slightly below level of Prc₁; Prc3–4 on vertical or nearly vertical line, well behind Prc₂. Supracaudal and infracaudal scales well developed, infrequently with a single, or even two (found once), separated luminous scales preceding the solid infracaudal gland. No secondary photophores found.

TABLE 2.—Measurements of Nannobrachium nigrum as thousandths of standard length with notes on allometry (for explanation see “Materials and Methods”).

FIGURE 5.—Distributions and localities for material examined for species of the Nigrum Group.

TABLE 3.—Photophore position characters helpful to separate specimens of N. atrum from N. nigrum.

N. atrum | N. nigrum
VLO above pelvic-fin base or above origin of pelvic fin | VLO at end of pelvic-fin base or behind vertical from pelvic-fin base
PO₄ tends to be above PO₃ or slightly anterior to vertical from PO₃ | PO₄ above or slightly posterior to vertical from PO₃
SAO₃ tends to be well before vertical from AOa₁ | SAO₃ slightly before vertical from AOa₁ or on vertical (sometimes slightly behind)
SAO₂ tends to be closer to VO₄ than to AOa₁ | SAO₂ tends to be equidistant or closer to AOa₁
Pol under adipose-fin base—usually under center of adipose-fin base | Pol under origin to center of adipose-fin base
Line through VLO and SAO₁ tends to pass through VO₃ or slightly behind it—usually well before VO₄ | VLO-SAO₁ line passes through VO₄ or slightly behind it—as far as midway between VO₄ and AOa₁

Size: The largest specimen examined was 111 mm. Previously the maximum size for this species was reported by Clarke (1973) as being less than 90 mm for a specimen given as L. niger (Form B) from north of Hawaii.

Material: 1,798 (13–111 mm) specimens were examined, including the holotype, 103 mm, BMNH 1887.12.7:219, collected south of the Philippines in 1875 by H.M.S. Challenger.

DISCUSSION.—It is now clear that, in many cases, both of the two new species in the Nigrum group were confused with N. nigrum, as were various other species of Nannobrachium. Table 3 can assist in distinguishing specimens of N. nigrum from N. atrum, which have frequently been confused in the literature.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium nigrum is restricted to the tropical Pacific Ocean, primarily the western and central portions, and to the extreme eastern tropical Indian Ocean (Figure 5). No consistent differences in frequencies of meristic characters were found between specimens from the central and western Pacific and those from the eastern Indian Ocean; however, a few differences in photophore positions were noted. Specimens from north of Hawaii tended to have the VLO photophore behind a vertical from the end of the pelvic-fin base more often than did specimens from the western Pacific. In addition, those from around Hawaii more frequently had the SAO₂ equidistant between the VO₄ and AOa₁, whereas western Pacific specimens commonly had the SAO₂ closer to the AOa₁ than to the VO₄.

One 65 mm specimen from off New Caledonia (ORSTOM, collection number FAB 22) had such a high gill-raker count (6 + 14, left side, 5 + 14, right side + 10 tooth patches) that for some time it was seriously thought to represent another new species; however, photophore characters that could be checked were most similar to N. nigrum, although the SAO arrangement in this specimen somewhat resembled that of N. atrum. In addition, four specimens from various locations in the southwest Pacific proved to have a mixture of typical and high gill-raker counts (6+14, 1 count; 6+13, 2 counts; 5+13, 3 counts; 5+12, 2 counts). These extremely high counts were not entered in either Tables A1 or A3. Unfortunately, these specimens were in a poorer condition than the original 65 mm specimen. The interim conclusion, therefore, is to consider these specimens examples of intraspecific variability.

Fujii (1984:69) discussed the distribution of this species and gave a description based on two large specimens taken by mid- water trawl near the Ogasawara Islands (∼27°N, 143°E). Although his general discussion undoubtedly dealt with this species, the two above-mentioned specimens are almost certainly a different species because of their large size (“SL 19, 21 cm,” which is twice as large as the largest specimens I examined), high dorsal-fin ray, anal-fin ray, and AO counts, Pol “well in advance of origin of adipose fin” (rather than below adipose-fin base, see Table 3), and lower VLO position relative to the lateral line (frequently nearly touching the lateral line in N. nigrum). The identification of the two specimens is problematical; the large size and the Pol and VLO positions suggest N. lineatum as a possibility, but the dorsal-fin ray, anal-fin ray, and AO counts are too low for the ranges I recorded for Indo-Pacific specimens of N. lineatum (Table A10).

Nannobrachium atrum (Tåning, 1928), new combination

FIGURE 6, TABLES 4, 5

Lampanyctus ater Tåning, 1928:68 [original description, North Atlantic]; 1932, pl. 128 [description, figure].—Parr, 1928:88, 104–106 [key, western Atlantic, figured, description].—Nybelin, 1948:40 [eastern Atlantic].—Bolin, 1959:33 [discussion, distribution].—Bullis and Thompson, 1965:28 [northern Gulf of Mexico].—Bekker, 1967a: 116 [equatorial Atlantic and Sargasso Sea].—Nafpaktitis and Nafpaktitis, 1969:44–45, fig. 53 [description, South Indian, lectotype figured, listed as holotype].—Quero, 1969:4 [northeastern Atlantic].—Badcock, 1970:1026 [discussion, depth distribution, Canary Islands].—Gibbs and Roper, 1971:129 [diurnal vertical migration].—Gibbs et al., 1971:43, 105–106 [key, vertical distribution near Bermuda, figure].—Hulley, 1972:225 [description]; 1981:188–190 [description, Atlantic distribution]; 1984a:62, 79–82, figs. 12, 13 [in part] [description]; 1984b:461 [description, northeast Atlantic distribution]; 1986b:243 [zoogeography]; 1986c:307, fig. 86.75 [description, South Africa, figure]; 1990:163, 164 [figured, Southern Ocean].—Krefft and Bekker, 1973:187 [biology, synonymy].—Nafpaktitis, 1973:38–40 [redescription, designation of lectotype, figure].—Nielsen, 1974:38 [listing of lectotype].—Parin et al., 1974:106 [southwest Atlantic].—Bekker et al., 1975:314 [distribution, Caribbean Sea].—Badcock and Merrett, 1976:42 [30°N, 23°W].—Brooks, 1976:569, 575, 581 [swimbladder size].—Parin and Golovan, 1976:263 [off West Africa].—Wisner, 1976:175 [figure, discussion].—Nafpaktitis et al., 1977: 203–206, fig. 139 [description, distribution, figure].—Backus et al., 1977:267, 275, 277 [zoogeography].—Parin et al., 1978:175 [?in part?] [eastern tropical Atlantic].—Paxton, 1979:14 [lectotype].—Gushchin and Kukuev, 1981:37 [in part?] [53°N, 30°W].—Brandt, 1983:235, 240 [?in part?] [in warm core eddy east of Australia].—Moser et al., 1984:239 [relationships, larval description].—Hulley and Krefft, 1985:35, 40–46 [North Atlantic zoogeography].—Rubies, 1985:578, 584 [Valdivia Bank off Namibia, gill raker numbers].—Gartner et al., 1987:86, 88, 91, 95 [eastern Gulf of Mexico].—Kailola, 1987:103 [?in part] [Solomon Sea].—Kamella, 1987:52, 102–105, 149–159, 164 [ecology and biology near Bermuda].—Scott and Scott, 1988:221 [description, Nova Scotian shelf].—Paxton and Hanley, 1989:264 [Australian distribution].

Lampanyctus niger.—Norman, 1930:331 [in part] [Discovery Expeditions].—[Not Günther, 1887.]

Macrostoma atrum.—Fowler, 1939:1231 [repeats original description].

Lampanyctus (Lampanyctus) ater.—Fraser-Brunner, 1949:1086 [illustrated key].—Bekker, 1983:87, 88, 199, 200 [key, description, distribution].

?Lampanyctus niger.—Smith, 1949:123 [description, South Africa, figure] [determination fide Hulley, 1986c:307].—[Not Günther, 1887.]

Paralampanyctus ater.—Kotthaus, 1972b:29 [western tropical Indian].—Kotthaus, 1972a: 14 [in part?] [eastern North Atlantic].

Lampanyctus niger-ater complex.—McGinnis, 1982:41–43, 66 [distribution south of 30°S, relationships, zoogeography].

FIGURE 6.—Nannobrachium atrum (Tåning, 1928). Drawing of 102 mm specimen, USNM 298182, Atlantic Ocean, 32°16′N, 64°21′W. (Scale bar=1 cm.)

COMPARATIVE DIAGNOSIS.—Nannobrachium atrum (Figure 6) can be distinguished from the other species of the Nigrum group and from N. crypticum in the Achirus group primarily by its gill raker count (total 16–18) and number of lower limb tooth patches on the second gill arch (7.5–10) (both higher than in N. gibbsi, N. indicum, and N. crypticum) and by the number of its AO photophores (12–15), lateral line organs (36–39), and vertebrae (36–39) (all higher than in N. nigrum, N. indicum, and N. crypticum) (Table A1). In addition, the SAO series is farther forward in N. atrum than it is in N. nigrum. It can be distinguished from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 56 specimens from the North and South Atlantic, Indian, and South Pacific oceans and are given in Tables A1–A8.

Proportions: Given in Table 4.

TABLE 4.—Measurements of Nannobrachium atrum as thousandths of standard length with notes on allometry.

TABLE 5.—Nannobrachium atrum, comparison of selected meristics of specimens from the North and South Atlantic, Indian, and South Pacific oceans.

Fins: Origin of anal fin behind vertical from middle of base of dorsal fin. Pectoral fin barely reaching vertical from PO₃, its rays weak, flexible. Base of adipose fin above end of anal-fin base, its origin well before end of anal-fin base.

Luminous Organs: PLO 1–3 times its diameter below lateral line. PO₄ slightly higher than level of PVO₂ and above PO₃ or slightly anterior to vertical from PO₃. VLO less than one photophore diameter below, frequently nearly touching, lateral line. SAO₂ always behind vertical from VO₄ but usually closer to VO₄ than to AOa₁. SAO₃ before vertical from AOa₁. AOa₁ slightly depressed and AOa1–2 interspace enlarged. AOp₁ at or behind end of anal-fin base. Prc well separated from AOp; Prc1–2 on horizontal line; Prc3–4 on or nearly on vertical line, well behind Prc₂. Supracaudal and infracaudal luminous scales well developed, often with single separated scale preceding infracaudal gland. No secondary photophores found.

Size: The largest specimen examined was 133 mm from off New Zealand, whereas the largest specimen examined from the Atlantic was 119 mm, taken by the Walther Herwig in the North Atlantic. Nafpaktitis et al. (1977) suggested that this species may attain a maximum size of 140 mm. Hulley (pers. comm., 1980) reports a size of 129 mm and suggests sexual maturity at about 90–100 mm. The largest specimen that he examined from South Atlantic Walther Herwig material was 120.2 mm (Hulley, 1981).

Material: 741 (20–133 mm) specimens were examined, including the lectotype, 89 mm, ZMUC P2330209, Dana sta 1152 1, 30° 17′N, 20°44′W, 22 October 1921.

DISCUSSION.—Although the distinctness of N. atrum from N. nigrum has been questioned in the past (Bolin, 1959; Nafpaktitis and Nafpaktitis, 1969; Nafpaktitis, 1973; Wisner, 1976), there is no doubt that they are distinct. Individual specimens, however, are not always easily separable, especially if damaged or distorted in preservation, as is frequently the case. The number of lateral line pores is an excellent diagnostic character, as are the number of vertebrae and, to a lesser extent, anal-fin rays. Table 3 can help identify specimens, especially those that are well preserved and not distorted.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium atrum, the most widely distributed species of Nannobrachium, is found in the South Pacific and Indian oceans and in the Atlantic Ocean, where it is bipolar and absent from the central area (Figure 5). Nafpaktitis et al. (1977) reported N. atrum to have a daytime maximum abundance in the North Atlantic at 700–800 m and to be as shallow as 100 m at night. Karnella (1987) reported greater depth ranges for Ocean Acre material, with a late spring maximum at 1051–1100 m.

Despite the broad distribution, no differences were found in absolute numbers or frequencies of gill rakers on the first arch, lower limb tooth patches of the second arch, or body shape that would show up as proportional differences. Only slight differences were found in the frequencies of AOp and total AO photophore counts, dorsal- and anal-fin ray counts, and numbers of infracaudal luminous gland scales (Table 5). Southwest Pacific specimens tended to have the VLO rather far posteriad, which was the only photophore positional difference. No differences were noted in specimens from the eastern and western North Atlantic and the Gulf of Mexico.

Two specimens, one from the Indian Ocean and one from the Pacific, with exceptionally high numbers of anal-fin rays (21), deserve special comment. The Indian Ocean specimen (LACM 31332-4, 69 mm) was collected by the Anton Bruun and, thus, was part of the material described by Nafpaktitis and Nafpaktitis (1969:44). In addition to the high number of anal-fin rays, it is atypical both in the lower-limb tooth patch count on the second gill arch (10 on both sides versus the common number of 9 or rarely 10 on one side in typical N. atrum) and in its count of 8 AOa plus 6 AOp (both sides). A further mystery is the origin of this specimen. The bottle label lists only one specimen (86 mm) instead of the two it actually contains. Nafpaktitis and Nafpaktitis (1969:44) listed the material of N. atrum that they examined from the Indian Ocean and included the 86 mm specimen as the only one from that collection (label number 7133). They recorded neither the 69 mm specimen nor the atypical AO count of 8+6 in their table 9, so it appears that they did not see it.

The Pacific Ocean specimen with 21 anal-fin rays (ZMUC, Dana 3631 III, 96.5 mm) is from 35°40′S, 176°40′E, which is north of New Zealand. Besides the anal-ray count, it has two abnormalities: a gill raker count of 5 + 11 on the right side (the left side is the typical N. atrum count of 5 + 12) and the SAO₂ slightly far back in position so that it is closer to the AOa₁ than to the VO₄ (as is typical in N. nigrum). Determination of the status of these specimens requires study of more material.

FIGURE 7.—Nannobrachium gibbsi, new species. Drawing of holotype, 107.5 mm, ZMUC, Dana sta 3570 I, Pacific Ocean, 14°01′S, 147°51′W. (Scale bar=1 cm.)

One other atypical and damaged specimen is in the collections of the South African Museum (SAM 23712), and it came from the South Atlantic. It appears to be a typical specimen of N. atrum, except that the intact left VLO is far below the lateral line (about 4 photophore diameters). The pectoral-fin base is narrow, but the fins are badly broken, so it is impossible to estimate their original length, but the rays appear to be stiff enough that they resemble some specimens of the Regale group. In all other characters, considering the damaged condition, it is a fairly typical specimen of N. atrum, except for a gill raker count on the right side of 5 + 13 (but with a more typical 5+12 on the left side). Again, determination of status awaits further study.

Nannobrachium gibbsi, new species

FIGURE 7, TABLE 6

Lampanyctus achirus.—Craddock and Mead, 1970:28 [in part] [southeast Pacific].—[Not Andriashev, 1962.]

Lampanyctus (Lampanyctus) niger.—Bekker, 1983:87–89, 198–200 [?in part] [key, description, distribution].—[Not Günther, 1887.]

TYPE SPECIMENS.—Holotype: Female 107.5 mm; ZMUC Dana sta 3570 I, 14°01′S, 147°51′W, 10 July 1928.

Paratypes: SIO 72-303, 1 (122 mm); SIO 72-306, 2 (23–54 mm); SIO 72-312, 2 (62–62 mm); SIO 72-313, 3 (31–111 mm); SIO 72-316, 2 (29–29 mm); SIO 72–320, 1 (117 mm); SIO 75-631, 1 (32 mm); UBC 13, 1 (93 mm); USNM uncat. (16°S, 168°04′W, 7 Dec 1967), 1 (89 mm); USNM 298168, 1 (93 mm); USNM 303311, 5 (38–59.5 mm); ZMUC 35-761, 1 (104 mm); ZMUC 35-858, 2 (98–99 mm); ZMUC 35-862, 1 (47 mm); ZMUC 35-879, 1 (74 mm); ZMUC 35-881, 1 (81 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium gibbsi (Figure 7) can be distinguished from the other species of the Nigrum group primarily by its gill raker count (total 13–15) and number of tooth patches on the lower limb of the second gill arch (7–8) (both lower than in N. atrum and N. nigrum); by the number of AO photophores (13–14), anal-fin rays (17–20), and vertebrae (36–38) (all higher than in N. nigrum and N. indicum); and by the number of lateral line organs (33–35) (lower than in N. atrum but higher than in N. indicum) (Table A1). It can be distinguished from all other species of Nannobrachium by the combination of characters in Table 1 and can be further distinguished from N. crypticum in the Achirus group by its higher number of AO photophores, anal-fin rays, and vertebrae (Table A1).

DESCRIPTION.—Counts are based on up to 62 specimens from the Pacific Ocean and are given in Tables A1–A8. Counts for the holotype are D 15, A 19, P₁ 13?, 14?, GR 4+10, tooth patches 8, AO 8+6, SC/IC art, LL 35?, V 16+21.

Proportions: Given in Table 6. Holotype measurements (in mm) as follows: SL 107.5, HD 16.0, PDD 16.8, CPD 8.9, CPL 21.4, PADL 23.0, PDL 50.4, PPL 42.5, PANL 59.2, PAL 17.1, HL 28.6, UJL broken, SOL 4.8, ED 5.6, SGL 6.5, IGS 12.4, IGEL 12.4, AFB, 26.0, DFB 19.6, AF 10.2.

Fins: Origin of anal fin behind vertical from middle of base of dorsal fin. Pectoral fins with weak and flexible rays, not reaching beyond vertical from PO₃, except in small specimens where they may reach beyond PO₄. Adipose-fin base above end of anal-fin base, with adipose origin well in advance of end of anal-fin base.

Luminous Organs: PLO 1–2 photophore diameters below lateral line (approximately 2 diameters below in holotype). PO₄ slightly below or approximately on level of PVO₂ and above or slightly behind a vertical from PO₃ (PO₄ on level of PVO₂ and behind vertical from PO₃ in holotype). PVO₂ before upper edge or center of pectoral-fin base (PVO₂ before upper edge in holotype); PVO1–2 interspace art–art of PVO₂–PLO distance (approximately art in holotype). VLO 1–2 photophore diameters below lateral line (two diameters below in holotype). SAO₂ above but variable in relation to vertical from AOa₁ (SAO₂ before vertical from AOa₁ in holotype). AOa₁ not notably depressed; AOa1–2 interspace slightly enlarged. AOp₁ behind end of anal-fin base. Prc well separated from AOp; Prc1–2 on horizontal line; Prc3–4 on or nearly on vertical line, well behind Prc₂ although Prc₃ occasionally forward as much as a full photophore diameter before vertical from anterior margin of Prc₄ (Prc₃ on vertical through anterior margin of Prc₄ in holotype). Supracaudal and infracaudal luminous glands well developed, infrequently with single separated luminous scale preceding solid infracaudal gland. No secondary photophores found.

TABLE 6.—Measurements of Nannobrachium gibbsi as thousandths of standard length with notes on allometry.

Size: The largest known specimen is 122 mm.

Material: 190 (17–120 mm) specimens not designated as type material were examined.

DISCUSSION.—This species has been confused with both N. nigrum and N. atrum, which have nearly identical photophore patterns. They differ primarily in number of gill rakers on the first arch and number of tooth patches on the lower limb of the second gill arch. Although the differences are rather slight, they are consistent; however, fresh or freshly preserved specimens of N. gibbsi apparently look different from similar specimens of N. nigrum. When both species were collected together in the same midwater trawl sample aboard the R.V. Eltanin during a transect of the central Pacific, R.H. Gibbs, Jr., was able to recognize them as distinct, although he did not know which, if either, represented the true N. nigrum (pers. comm., 1977).

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium gibbsi occurs mainly in the tropical Pacific (Figure 5). Examination of material from the extreme eastern and western ends of its range revealed no consistent variation.

ETYMOLOGY.—It is a pleasure to name this species after the late Dr. Robert H. Gibbs, Jr., of the Smithsonian Institution, in honor of his many contributions to our understanding of open-ocean midwater ichthyology. It is particularly appropriate in this case because he was first, as far as I am aware, to recognize the distinctness of specimens of this species.

Nannobrachium indicum, new species

FIGURE 8, TABLE 7

Lampanyctus sp.—Norman, 1939:29 [in part] [Gulf of Aden, Arabian Sea].

Lampanyctus sp. I.—Nafpaktitis and Nafpaktitis, 1969:42–43 [description and distribution].

Lampanyctus sp. II.—Nafpaktitis and Nafpaktitis, 1969:43–44, fig. 52 [description, figure].

Paralampanyctus sp.—Kotthaus, 1972b:29 [?in part] [southern tropical Indian Ocean].

Lampanyctus (Lampanyctus) niger.—Bekker, 1983:87–89, 198–200 [in part] [key, description, distribution].—[Not Fraser-Brunner, 1949.]

Lampanyctus sp. A.—Hulley, 1984a:63, 83–84, fig. 14 [description]; 1986c: 309–310, figs. 86, 88 [description, figure, off South Africa].

FIGURE 8.—Nannobrachium indicum, new species. Drawing of holotype, 67 mm, ZMUC, Dana sta 3912 II, Indian Ocean, 6°52′N, 79°30′E. (Scale bar= 1 cm.)

TYPE SPECIMENS.—Holotype: Female, 67 mm, ZMUC Dana sta 3912 II, 6°52′N, 79°30′E, 24 February 1929.

TABLE 7.—Measurements of Nannobrachium indicum as thousandths of standard length with notes on allometry.

Paratypes: LACM 31-3411, 1 (50 mm); LACM 31-3451, 1 (56 mm); LACM 31–3461, 5 (26–65 mm); LACM 31–3551, 2 (63–67 mm); LACM 31–3582, 1 (37 mm); LACM 31-3612/7217, 3 (59–61 mm); LACM 31-3661, 2 (54–55 mm); LACM 31-3892, 1 (58 mm); USNM 268397, 3 (60–69 mm); ZMUC 35-776, 1 (104 mm); ZMUC 39-12, 18 (44–78 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium indicum (Figure 8) can be distinguished from the other species of the Nigrum group and from N. crypticum in the Achirus group primarily by its gill raker count (total 14–17) (typically higher than in N. crypticum and N. gibbsi but lower than in N. atrum and N. nigrum) (Table A1) and by the number of luminous caudal-gland scales (1–3 / o–i+2–5), AO photophores (9–12), lateral line organs (29–32), and vertebrae (32–34) (typically lower than in all other species of Nannobrachium, except the same number of infracaudal luminous gland scales and vertebrae as in N. idostigma). In addition, it can be distinguished from all other Nannobrachium species by the combinations of characters in Table 1.

DESCRIPTION.—Counts are based on up to 29 specimens from the Indian Ocean and are given in Tables A1–A8. Counts for the holotype are D 14, A 17, P₁ ?, GR 4+11, tooth patches 8, AO 4+7, SC/IC art, LL 32, V15+18.

Proportions: Given in Table 7. Holotype measurements (in mm) as follows: SL 67, HD 11.4, PDD 10.0, CPD 6.6, CPL 14.6, PADL 13.6, PDL 31.4, PPL 27.4, PANL 40.3, PAL 10.9, HL 19.7 (damaged), UJL 14.3, SOL 4.1, ED 4.2 (damaged), SGL 3.9, IGS 5.4, IGEL 5.4, AFB 5.6, DFB 11.9, AF 6.7.

Fins: Origin of anal fin under middle of base of dorsal fin. Pectoral fin barely reaching vertical from VO₃, its rays very weak and flexible. Base of adipose fin above end of anal-fin base, with adipose origin well in advance of end of anal-fin base.

Luminous Organs: PLO 1–2 photophore diameters below lateral line (about 2 diameters below in holotype). PO₄ slightly higher than level of PVO₂ and above or behind vertical from PO₃ (PO₄ slightly behind vertical from PO₃ in holotype). VLO touching, or nearly touching, lateral line (VLO nearly touching lateral line in holotype). SAO₂ position midway between VO₄ and AOa₁ variable, but frequently closer to AOa₁ (SAO₂ closer to AOa₁ in holotype). SAO₃ variably over AOa₁ (SAO₃ before vertical from AOa₁ in holotype). AOa₁ slightly depressed, and AO1–2 interspace enlarged. AOp₁ behind end of anal-fin base. Prc well separated from AOp; Prc1–2 on an approximately horizontal line; Prc3–4 on a vertical or nearly vertical line, well behind Prc₂. Supracaudal and infracaudal luminous scales well developed; infrequently with a single separated scale preceding the infracaudal gland. No secondary photophores found.

Size: Nannobrachium indicum is a small-bodied species of Nannobrachium, probably reaching a maximum size just over 100 mm.

Material: 57 (26–80 mm) specimens, excluding type material, were examined.

DISCUSSION.—Nafpaktitis and Nafpaktitis (1969) recognized this as two possible undescribed species, which they listed as Lampanyctus sp. I and Lampanyctus sp. II, but they did not describe them because of taxonomic uncertainty among the short-pectoral-finned species of Lampanyctus. Examination of their specimens, as well as additional material, shows that both L. sp. I and L. sp. II are N. indicum, representing examples of intraspecific variability.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium indicum is the only species of Nannobrachium evidently restricted to the Indian Ocean, where it is limited to the Equatorial Region (Figure 5). No geographic variation was noted in material examined from the extreme eastern and western ends of the range. The two specimens from off the east coast of South Africa, which Hulley (1984a, fig. 14) reported as Lampanyctus sp. A, appear to be fairly typical specimens of this species, although they were captured far to the south of any other specimens I examined. They may represent expatriates carried south by the Agulhas current system.

FIGURE 9.—Nannobrachium regale (Gilbert, 1891). Drawing of 81 mm specimen, USNM 108161. Specimen is a paratype of L. micropunctatus Chapman, Pacific Ocean, 56°06′N, 152°09′W. (Scale bar= 1 cm.)

ETYMOLOGY.—The name is an adjective referring to the Indian Ocean.

The Regale Group

Two unique characters distinguish the species of this group: low position of the VLO on the side of the body and relatively robust pectoral-fin development. At a distance of three photophore diameters or more below the lateral line, the VLO is remote from the lateral line, always further than the PLO is from the lateral line. The pectoral fins are relatively strong and well developed, usually reaching beyond the pelvic-fin insertion, with moderately thick but rather flexible rays. Pectoral fins are better developed in this group than in any other Nannobrachium group. They are poorly developed, however, compared to the pectoral-fin development in most species of Lampanyctus, and accurate counts of pectoral-fin rays can only be made with difficulty. The species in the other Nannobrachium groups either lack pectorals or have pectorals with short, thick, and stiff rays, or they have pectorals with short, thin, and flexible rays.

Another character shared by species in the Regale group, but not unique to them, is the position of Prc₃ below Prc₄ but on a vertical from the anterior edge of Prc₄.

These and other characters are compared in Table 1 for all the species groups of Nannobrachium.

The Regale group contains five species: N. regale (Gilbert, 1891), N. ritteri (Gilbert, 1915), N. idostigma (Parr, 1931), N. fernae (Wisner, 1971), and N. bristori, new species. Modal characters of all species in the Regale group are listed in Table A9.

Nannobrachium regale (Gilbert, 1891)

FIGURE 9, TABLE 8

Myctophum regale Gilbert, 1891:544 [original description].—Böhlke, 1953:21 [paratype originally at Stanford University, now in California Academy of Sciences].—Paxton, 1979:13 [holotype and paratypes].

Nannobrachium regale Goode and Bean, 1896:512 [original description cited].—Jordan and Evermann, 1896a:300 [original description cited]; 1896b:563 [key, description].—Jordan et al., 1930:168 [original description cited].

Myctophum (Lampanyctus) regale Brauer, 1904:396 [?in part] [California]; 1906:385 [?in part] [California].

Lampanyctus regalis.—Parr, 1928:89 [synonymy in key]; 1929:24–25 [discussion, holotype figured].—Barnhart, 1936:21 [description, San Diego to Monterey, California].—Bolin, 1939:144–147 [description, comparison, figures].—Follett, 1952:412 [off central California].—Rass, 1955:328 [not seen, fide Pearcy et al., 1979; Kurile-Kamchatka area, Bering Sea]; 1968: 233, 237, 241 [distributional analysis].—Aron, 1959:414 [North Pacific, west of Aleutians].—Kulikova, 1960:34–39 [distribution, description].—Parin, 1961:262 [distribution].—Bekker, 1964:474 [distribution]; 1967b:179 [distribution].—Berry and Perkins, 1966:662 [eastern Pacific].—Paxton 1967a:432 [vertical distribution off southern California].—Fitch and Lavenberg, 1968:44 [California waters].—Ahlstrom, 1969:42 [California Current larvae].—Fitch, 1969:7 [otoliths].—Bailey et al., 1970:19 [common name—Pinpoint lampfish].—Ebeling et al., 1970b:12–15 [ecology off southern California].—Makushok, 1970:541 [Kurile-Kamchatka Trench].—Butler and Pearcy, 1972:1145–1149 [swimbladder].—Fedorov, 1973a:3; 1973b:42 [neither seen, fide Pearcy et al., 1979] [Bering Sea].—Briggs, 1974:316 [north boreal distribution].—Brown, 1974:28 [ecology off southern California].—Chen and Ebeling, 1974:841, 845, fig. 12 [karyotype].—Moser and Ahlstrom, 1974:406–407 [larvae figured].—Wisner, 1976:173 [description, distribution, figure].—Richardson and Pearcy, 1977:129 [larvae off Yaquina Bay, Oregon].—Frost and McCrone, 1978:755 [North Pacific, stations P and Q].—Childress and Somero, 1979:276 [enzymatic activities].—Lancraft and Robison, 1979:714 [net feeding].—Pearcy et al., 1979:129, 131 [Bering Sea, literature records].—Childress et al., 1980:28–33 [growth and energy relations].—Robins et al., 1980:21 [common name—Pinpoint lampfish].—Novikov et al., 1981:33 [Emperor Seamount Ridge].—Parin and Fedorov, 1981:74–78 [zoogeography].—Neighbors and Nafpaktitis, 1982:208–210, 212–213 [lipid composition].—Willis and Pearcy, 1982:92–93 [vertical distribution off Oregon].—Amaoka et al., 1983 [not seen, fide, H.G. Moser] [description, occurrence in northwestern Pacific].—Sawada, 1983:90–91, 236–237 [Japanese], 185, 318 [English], pis. 43, 126 [description, distribution, distinguished from L. ritteri].—Moser et al., 1984:238–239, fig. 124c [larva figured, relationships].—Fujii, 1984:69, pl. 66-L [description, distribution].—Stein, 1985:190 [large net capture].—Willis et al., 1988:122 [distribution].—Matarese et al., 1989, unpaginated [not seen, fide H.G. Moser] [larvae, occurrence in northeastern Pacific].—Moser et al., 1993:162–163 [distribution and abundance in California Current region].—Paxton et al., 1995:1315 [listed; not seen, fide J. Paxton].

Lampanyctus micropunctatus Chapman, 1939:527–530 [original description, northeast Pacific].—Fraser-Brunner, 1949:1085 [synonymized with L. regalis].—Böhlke 1953:19–20 [paratype originally at Stanford University, now at California Academy of Sciences].—Paxton, 1979:13 [holotype and paratypes].

Lampanyctus (Lampanyctus) regalis.—Fraser-Brunner, 1949:1058 [illustrated key].—Bekker, 1983:84, 85, 194, 196 [key, description, distribution].

Nannobrachium regalis.—Moser and Ahlstrom, 1996:422–423 [early life history and larvae illustrated].

TABLE 8.—Measurements of Nannobrachium regale as thousandths of standard length with notes on allometry.

COMPARATIVE DIAGNOSIS.—Nannobrachium regale (Figure 9) can be distinguished from all other species in the Regale group, except N. ritteri, by its lower number of gill rakers (total 13–15), higher number of dorsal-fin rays (15–16), and forward position of the SAO photophores (Table A9). It can be separated from N. ritteri by the higher position of its VLO (above a line connecting PLO and SAO₁ in N. regale) and its larger adipose fin (adipose-fin length less than twice into the caudal peduncle depth in N. regale). It can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 25 specimens from the North Pacific Ocean and are given in Tables A2–A9.

Proportions: Given in Table 8.

Fins: Origin of anal fin behind vertical from middle of base of dorsal fin. Pectoral fins reaching beyond end of pelvic-fin base; well developed with rather robust, stout rays. Base of adipose fin above or slightly before end of anal-fin base.

Luminous Organs: PLO 1–3 photophore diameters below lateral line. PO₄ usually higher than level of PVO₂ and on or behind vertical from PO₃. VLO well below lateral line but typically well above midway between lateral line and pelvic-fin base and, therefore, closer to lateral line than to pelvic-fin base; VLO above line connecting PLO and SAO₁ and above line extended through SAO1–2. SAO₁ above VO2–3 interspace; SAO₂ behind vertical from VO₄ but typically much closer to VO₄ than to AOa₁ Both SAO₁ and SAO₂ rather low on body, much closer to level of VO series than to SAO₃, which is immediately below lateral line and forward of vertical from AOa₁. Line connecting the VLO and SAO₁ typically passing through VO₄ or anal-fin origin, certainly much below SAO₂. AOa₁ usually slightly depressed and AOa1–2 interspace frequently somewhat enlarged. AOp₁ at or near end of anal-fin base. Upper Pol under adipose-fin base, typically on or behind vertical from middle. Prc usually continuous with AOp; Prc₃ approximately on vertical midway between Prc₂ and Prc₄ but much closer to Prc₂. Supracaudal and infracaudal scales well developed; usually with one or, less commonly, with two separated scales preceding infracaudal gland and very rarely one separated scale preceding supracaudal gland. Minute, secondary photophores on posterior border of some scale pockets, especially on upper half of body.

Size: This is a large species of Nannobrachium. The largest specimen examined was 183 mm from Sagami Bay, Japan (see discussion under “Distribution and Geographic Variation”). A number of specimens examined from the eastern Pacific were larger than 150 mm, with a maximum of 170 mm. Wisner (1976) recorded the size to about 165 mm but also discussed a larger form from off Oregon and possibly northern California reaching at least 170 mm (see discussion below).

Material: 198 (18–183 mm) specimens were examined, including the holotype, a female, 154 mm, USNM 44289, Albatross sta 2923, off San Diego, California.

DISCUSSION.—This is the only valid species of Nannobrachium that has been described more than once. Specimens from the North Pacific were described by Chapman (1939) as L. micropunctatus. The holotype (USNM 108142) and a series of paratypes of L. micropunctatus were carefully examined, and all proved to be typical specimens of N. regale.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium regale is restricted to the North Pacific (Figure 10), from the Bering Sea to the region east of Hokkaido, Japan, in the western Pacific (fide M. Fedorov, 1977, pers. comm., 1979; Wisner, 1976). In the eastern Pacific, Wisner (1976) gave the range from the Gulf of Alaska southward to off Magdalena Bay, Baja California, with a depth of capture as shallow as 50 m at night. The very large (183 mm) specimen from Sagami Bay (University of Tokyo, Nomi 26–ORI–200) was carefully examined for evidence of geographic variation, as was material from the western Pacific in the collections of the Zoological Institute, St. Petersburg, Russia. No consistent differences could be found between eastern and western North Pacific specimens. The specimen from Sagami Bay had a total of 15 AO photophores (both sides) and 19 anal-fin rays, both at the upper limit of counts for this species, but both counts also have been recorded from eastern Pacific specimens.

FIGURE 10.—Distributions and localities for material examined for species of the Regale Group.

FIGURE 11.—Nannobrachium ritteri (Gilbert, 1915). Drawing of 87 mm specimen, USNM 303312, Pacific Ocean, 30°39′N, 118°45.5′W. (Scale bar=1 cm.)

Wisner (1976:173) discussed a possible second form under this species having slightly higher numbers of dorsal-, anal-, and pectoral-fin rays, higher AO photophore and gill raker counts, and minor photophore positional differences. This suggestion was not corroborated by the present study.

Nannobrachium ritteri (Gilbert, 1915)

FIGURE 11, TABLE 9

Lampanyctus ritteri Gilbert, 1915:318 [original description, off San Clemente Island].—Parr, 1928:89 [key]; 1929:23–24 [discussion of holotype].—Jordan et al., 1930:167 [original description cited].—Bamhart, 1936:21 [description, San Diego to Monterey, California, figure].—Bolin, 1939:41–143 [description, comparison, figure].—Follett, 1952:412 [off central California].—Böhlke, 1953:20 [2 paratypes originally at Stanford University, now at California Academy of Sciences].—Aron, 1959:414–415 [North Pacific capture depths].—Parin, 1961:268–279 [distribution, gill structure]; 1971:82 [probable misidentification from Peru Current].—Aron, 1962:279, 301, 307 [?inpart] [distribution in northeast Pacific].—Bekker, 1964:474 [boreal and central Pacific]; 1967b:179 [distribution].—Pearcy, 1964:87 [?in part] [off Oregon].—Berry and Perkins, 1966:661–662 [eastern Pacific].—Paxton, 1967a: 429 [vertical distribution off southern California]; 1967b:214–216 [feeding habits, parasites]; 1979:13 [holotype and paratypes].—Rass, 1968:233, 237, 241 [distributional analysis].—Ahlstrom, 1969:42 [California Current larvae].—Fitch, 1969:7 [otoliths].—Ebeling et al., 1970a:5, 7, 14 [off Santa Barbara, California]; 1970b:11-18, 29, 35 [ecology off southern California].—Barham, 1971:109 [swimbladder].—Day, 1971:17 [?in part] [off Canada and Washington].—Butler and Pearcy, 1972:1145–1149 [swimbladder].—Miller and Lea, 1972:70–71 [description, California Current system, figure].—Beklemishev, 1973:294–298 [characteristics of distribution].—Brown, 1974:17, 28 [ecology off southern California].—Chen and Ebeling, 1974:841, 845, fig. 8 [karyotype].—Moser and Ahlstrom, 1974:406–407 [larva figured].—Friedl et al., 1976:611 [deep scattering layer relationships].—Wisner, 1976:170–172 [description, distribution, figure].—McNulty and Nafpaktitis, 1977:510–514 [pineal morphology].—Pearcy et al., 1977: 238–239 [depth distribution off Oregon].—Frost and McCrone, 1978:755, 759 [North Pacific, stations P and Q].—Childress and Somero, 1979:276–277, 281 [enzymic activities].—Lancraft and Robison, 1979:714 [net feeding].—Childress et al., 1980:28–35 [growth and energy relations].—Parin and Bekker, 1981:66 [zoogeographic relations].—Parin and Fedorov, 1981:74–75 [Gulf of Alaska].—Robison and Bailey, 1981:136–138 [sinking rate of feces].—Neighbors and Nafpaktitis, 1982:208–214 [lipid composition].—Eschmeyer and Herald, 1983:94 [family representative].—Sawada, 1983:91, 237 [Japanese], 185, 318 [English] [distinguished from L. regalis].—Moser et al., 1984:238–239, fig. 124A [larva figured, relationships].—Willis, 1984:167 [assemblage membership in northeastern Pacific].—Moser et al., 1987:97 [assemblage relationships] [not seen, fide J. Paxton].—Willis et al., 1988:90 [distribution].—Matarese et al., 1989, unpaginated [not seen, fide, H.G. Moser] [larvae, from northeastern Pacific].—Moser and Smith, 1993:654 [assemblage relationships in California Current].—Moser et al., 1993:44 [distribution and abundance in California Current].—Paxton et al., 1995:1315 [listed; not seen, fide J. Paxton].

Lampanyctus (Lampanyctus) ritteri Fraser-Brunner, 1949:1085 [illustrated key].—Bekker, 1983:85, 86, 193, 198 [in part?] [key, description, distribution].

Nannobrachium ritteri.—Moser and Ahlstrom, 1996:424–425 [early life history and larvae illustrated].

COMPARATIVE DIAGNOSIS.—Nannobrachium ritteri (Figure 11) can be distinguished from all other species in the Regale group, except N. regale, by its lower number of gill rakers and intermediate number of infracaudal luminous gland scales (Table A9). It can be separated from N. regale by the lower position of its VLO (below a line connecting PLO and SAO₁ in N. ritteri) and its smaller adipose fin (adipose-fin length more than twice into the caudal peduncle depth in N. ritteri). It can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 25 specimens from the North Pacific Ocean and are given in Tables A2–A9.

Proportions: Given in Table 9.

Fins: Origin of anal fin under middle of base of dorsal fin. Pectoral fins reaching beyond end of pelvic-fin base; well developed with rather robust, stout rays. Base of adipose fin above end of anal-fin base.

TABLE 9.—Measurements of Nannobrachium ritteri as thousandths of standard length with notes on allometry.

Luminous Organs: PLO 1–3 photophore diameters below lateral line. PO₄ usually slightly higher than level of PVO₂ and on vertical from PO₃. VLO slightly below midway between lateral line and pelvic-fin base. SAO₁ above or slightly before vertical from VO₃; SAO₂ usually above AOa₁; and SAO₃ above AOa1–2 interspace. Both SAO₁ and SAO₂ approximately midway between lateral line and level of the VO and AOa series. Line connecting VLO and SAO₁ passing through or near lower margin of SAO₂ and always much above AOa₁. AOa₁ often slightly depressed; AOa1–2 interspace often slightly enlarged. AOp₁ at end of anal-fin base. Upper Pol before or on vertical from origin of adipose fin. Prc usually continuous with AOp; Prc₃ approximately on vertical midway between Prc₂ and Prc₄ but low and much closer to Prc₂. Supracaudal and infracaudal scales well developed, lacking any separated scales preceding infracaudal gland. No secondary photophores found.

Size: Wisner (1976) listed the maximum size to about 120 mm, which is consistent with the maximum-sized specimen of 117 mm examined in this study (the holotype).

Material: 929 (18–117 mm) specimens were examined, including the holotype, 117 mm, USNM 75807, Monterey Bay, California, collected by the Albatross, sta 4513, 23 May 1904.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium ritteri is restricted to the northeast Pacific Ocean (Figure 10). Bekker, however (1983:198, fig. 91), gave a distribution pattern for N. ritteri that I cannot explain. In addition to the range off California, which corresponds well with my findings, Bekker showed N. ritteri to range off Central and South America, a distribution reminiscent of the southern part of an eastern tropical Pacific pattern, such as that of N. idostigma. I have seen no specimens of N. ritteri from that southern region, however, nor did Wisner (1976). The only supportive references I found were in Russian publications. Parin (1971) listed L. ritteri with a question mark as having been collected in the waters of the Peru Current during the fourth cruise of the R/V Akademik Kurchatov. In that paper, he did not indicate the number of specimens of any of the species, nor the localities at which the purported L. ritteri were taken, presumably because of their rarity. Beklemishev (1973:294–298), in a discussion of what he termed “far-neritic” (or “distant neritic”) species, used the “lampanictine ritteri group” as an example from the eastern Pacific, “which, possibly, belong to a single polymorphic species L. ritteri (Figure 2).” The “ritteri group” distribution map (Beklemishev, 1973, fig. 2) appears to be an approximate composite of the distribution of N. ritteri, N. idostigma, and perhaps the eastern portion of N. regale. Beklemishev attributed the distribution map to information from Andriashev, 1962; Bekker, 1967a; and Bekker, pers. comm., 1977. Then, in dealing with some specific examples of mesopelagic zoogeography in the Pacific, using myctophid distributions, Parin and Bekker (1981:64–70) discussed distributions of “far-neritic groups” in which they estimated that around 20 species show such distribution patterns. After discussing eastern tropical Pacific and western tropical Pacific distributions, they discussed two examples of a transition type of far-neritic distribution: one in the “neutral region between the subtropical and subpolar waters near South America (Hygophum bruuni, 1 species out of the Symbolophorus boops group)” and one “near California (Lampanyctus ritteri and possibly L. ingens).” In this discussion, there is no suggestion that L. ritteri might occur in the far-neritic waters off South America, so it is especially puzzling to see such a distribution pattern in Bekker's (1983) monograph. Bekker not only illustrated the range off Central America and northern South America (1983, fig. 91), he discussed that distribution (1983:198), specifically giving a north-south extent from about 50°N to 30°S, extending westward from the continent to 150°W at the north, to 100°W at the equator and to 80°W in the extreme south. In the absence of specimens, however, or at least the unequivocal identification of specific material of N. ritteri from off Central or South America, I must consider the southern distribution shown by Bekker to be in error.

FIGURE 12.—Nannobrachium idostigma (Parr, 1931). Drawing of 92.5 mm specimen, SIO H52-404, Pacific Ocean, 30°00′N, 100°00′W. (Scale bar=1 cm.)

Wisner (1976) reported the shallowest depth of capture of about 20 m during the night.

Nannobrachium idostigma (Parr, 1931)

FIGURE 12, TABLE 10

Lampanyctus idostigma Parr, 1931:32–34 [original description, eastern tropical Pacific].—Bolin, 1939:138–139 [description, comparison, figure].—Beebe and Van der Pyle, 1944:81 [eastern Pacific].—Bussing, 1965:203–204 [off Peru].—Berry and Perkins, 1966:662 [off Baja California].—Lavenberg and Fitch, 1966:96, 103 [Gulf of California].—Bekker, 1967b:179 [distribution].—Fitch and Brownell, 1968:2567 [otoliths in cetacean stomachs].—Ahlstrom, 1969:42 [California Current larvae]; 1972:1190 [possible larvae from eastern tropical Pacific].—Parin, 1971:82, 86–88, 90 [Peru Current]; 1975:321 [depth of capture at equator].—Robison, 1972:454–455 [Gulf of California].—Brewer, 1973:21–22 [Gulf of California].—Parin et al., 1973: 114–115 [eastern tropical Pacific].—Friedl et al., 1976:611 [deep scattering layer relationship].—Wisner, 1976:173–174 [description, distribution, figure].—Paxton, 1979:14 [holotype and paratypes].—Parin and Bekker, 1981: 66 [zoogeographic relations].—Neighbors and Nafpaktitis, 1982:208–210, 212–214 [lipid composition].—Robison and Craddock, 1983:285–296 [?in part] [Fraser's dolphin food item].—Loeb, 1986:179 [North Pacific depth distribution].—Paxton et al., 1995:1315 [listed] [not seen, fide J. Paxton].

Lampanyctus (Lampanyctus) idostigma.—Fraser-Brunner, 1949:1085 [illustrated key].—Bekker, 1983:84, 85, 194, 196 [key, description, distribution]. Nannobrachium idostigma.—Moser and Ahlstrom, 1996:416–417 [early life history, larvae illustrated].

COMPARATIVE DIAGNOSIS.—Nannobrachium idostigma (Figure 12) can be distinguished from all other species in the Regale group by its lower number of AO photophores, anal-fin rays, infracaudal luminous gland scales, lateral line organs, and vertebrae (Table A9). It can be separated from N. bristori by its low number of AO photophores, tooth patches on the lower limb of the second gill arch, and lateral line organs, and it can be distinguished from all the other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 25 specimens from the eastern Pacific Ocean and are given in Tables A2–A9.

TABLE 10.—Measurements of Nannobrachium idostigma as thousandths of standard length with notes on allometry.

FIGURE 13.—Nannobrachium fernae (Wisner, 1971). Drawing of 78 mm paratype, SIO 51-373, Pacific Ocean, 50°00′N, 150°00′W. (Scale bar=1 cm.)

Proportions: Given in Table 10.

Fins: Origin of anal fin before vertical from middle of base of dorsal fin. Pectoral fins reaching beyond end of pelvic-fin base; well developed with rather robust rays. Base of adipose fin above end of anal-fin base.

Luminous Organs: PLO art;–2 photophore diameters below lateral line. PO₄ usually slightly higher than level of PVO₂ and behind vertical from PO₃. VLO well below lateral line, typically midway between it and pelvic-fin base. SAO₁ above VO3–4 interspace; SAO₂ variably above AOa₁, often slightly before or behind vertical from leading edge of AOa₁. Both SAO₁ and SAO₂ about midway between ventral profile and lateral line. SAO₃ approximately over AOa₂. AOa₁ usually slightly depressed; AOa1–2 interspace slightly enlarged. AOp₁ above end of anal-fin base. Pol₂ typically well before vertical from origin of adipose fin. Prc usually continuous with AOp. Prc₃ usually slightly forward of vertical from Prc₄ but low and slightly closer to Prc₂. Supracaudal and infracaudal gland scales well developed; no separated scales preceding solid gland. No secondary photophores found.

Size: Wisner (1976) recorded the species to about 90 mm in length, which corresponds closely to the length of 96 mm in the largest specimen examined in this study.

Material: 585 (15–96 mm) specimens were examined.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium idostigma is restricted to the eastern tropical Pacific (Figure 10). Wisner (1976) reported that this species was taken only in tows that sampled at 300 m or deeper. No evidence could be cited for consistent geographic variation in this species.

Nannobrachium fernae (Wisner, 1971), new combination

FIGURE 13, TABLE 11

Lampanyctus fernae Wisner, 1971:50 [original description, North Pacific]; 1976: 172–173 [description, distribution, figure].—Paxton, 1979:14 [holotype and paratypes].—Willis et al., 1988:87 [distribution].

Lampanyctus (Lampanyctus) fernae.—Bekker, 1983:85, 86, 193, 198 [key, description, distribution].

COMPARATIVE DIAGNOSIS.—Nannobrachium fernae (Figure 13) can be distinguished from all other species in the Regale group primarily by the higher number of scales in its infracaudal luminous gland (Table A9), which is higher than in any other species of Nannobrachium. In addition, it can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 30 specimens from the North Pacific Ocean and are given in Tables A2–A9.

Proportions: Given in Table 11.

Fins: Anal-fin origin behind vertical from middle of base of dorsal fin. Pectoral fin reaching to or beyond pelvic-fin insertion, its rays relatively well developed and robust. Origin of adipose fin usually above end of anal-fin base.

Luminous Organs: PLO art;–2 photophore diameters below lateral line. PO₄ usually slightly higher than, but occasionally at, level of PVO₂ and behind vertical from PO₃. VLO well below lateral line, typically slightly closer to lateral line than to pelvic-fin base. SAO₁ variably above VO₃; SAO₂ closer to VO₄ than to AOa₁ level of SAO1–2 rather low on body, closer to ventral profile than to lateral line. SAO₃ on or before vertical from AOa₁; AOa₁ slightly depressed; AOa1–2 interspace slightly enlarged. AOp₁ above end of anal-fin base. Pol₂ well before vertical from origin of adipose fin. Pre frequently not continuous with AOp. Prc₃ on vertical line approximately midway between Prc₂ and Prc₄ but much closer to Prc₂. Supracaudal and infracaudal luminous gland scales well developed; no separated scales preceding solid glands.

Size: Wisner (1976) records the species as reaching a size of about 90 mm in length, which corresponds to the maximum length of 91 mm examined in this study.

Material: 62 (38–91 mm) specimens were examined.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium fernae appears to have the most restricted distribution of any species of Nannobrachium (Figure 10). It is known only from an area of the North Pacific between 40°N–45°N and 135°W–165°W, with a depth of capture as shallow as 200 m at night (Wisner, 1976). Additional material I have examined comes from the same general region, so apparently this species is truly so restricted. No geographic variation was found in material examined.

TABLE 11.—Measurements of Nannobrachium fernae as thousandths of standard length with notes on allometry.

Nannobrachium bristori, new species

FIGURE 14, TABLE 12

Lampanyctus niger.—Berry and Perkins, 1966:662 [?in part] [fide H.G. Moser; Pacific off California and northern Mexico].—Moser and Ahlstrom, 1974: 406–407 [larva figured].—[Not Günther, 1887.]

Lampanyctus niger (Form C).—Clarke, 1973:416, 418 [ecology north of Hawaii].—[Not Günther, 1887.]

Lampanyctus (Lampanyctus) niger.—Bekker, 1983:87–89, 198–200 [?in part?] [key, description, distribution],—[Not Fraser-Brunner, 1949]

Lampanyctus sp.—Moser et al., 1984:238, fig. 124D [larva figured].

Nannobrachium “niger”—Moser and Ahlstrom, 1996:418–419 [early life history and larvae illustrated].

TYPE SPECIMENS.—Holotype: Male, 110 mm, SIO 71-301, 27°26.6′N, 155°24.6′W, 30 September 1971.

Paratypes: HIMB 70–913, 2 (34–67 mm); HIMB 70–914, 18 (21–40 mm); HIMB 70–916, 4 (33–40 mm); HIMB 70–927, 2 (58–86 mm); OS 12816, 1 (74 mm); OS 12815, 4 (33–116 mm); SIO 51–84, 1 (57 mm); SIO 66–20, 2 (72–76 mm); SIO 67–56, 1 (73 mm); SIO 71–301, 3 (40–120 mm); SIO 71–310, 1 (111 mm); SIO 73–145, 1 (142 mm); SIO 73–160, 1 (105 mm); SIO 76–6, 1 (46 mm); SIO 73–329 (28°03′N, 154°39′W, 22 June 1973), 1 (68 mm); USNM 298174, 8 (30–91 mm); USNM 298191, 1 (101.5 mm); USNM 298192, 2 (32.5–47 mm); USNM 359634 (25°02′N, 137°55′W, 19 Nov 1967), 1 (106 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium bristori (Figure 14) can be most easily distinguished from the other species in the Regale group by its number of AO photophores (fewer than in N. ritteri, more than in N. idostigma), number of gill rakers and lower limb tooth patches on the second gill arch (more of both than in N. regale and N. ritteri, more tooth patches than in N. idostigma), and number of infracaudal luminous gland scales and lateral line organs (fewer of both than in N. regale and N. ritteri, fewer lateral line organs than in N. fernae and more than in N. idostigma) (Table A9) Nannobrachium bristori can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 23 specimens from the North Pacific Ocean and are given in Tables A2–A9. Counts for the holotype are D 14, A 18, P₁ 16?, GR 4+11, tooth patches 9, AO 5+7 (L), 6+7 (R), SC/IC art?, LL 37?, V 16+21.

Proportions: Given in Table 12. Holotype measurements (in mm) as follows: SL 110, HD 17.5, PDD 17.7, CPD 9.6, CPL 26.4, PADL 24.3, PDL 47.0, PPL 41.0, PANL 58.5, PAL 16.3, HL 31.3, UJL 22.9, SOL 4.9, ED 6.4, SGL 4.9, IGS 7.6, IGEL 7.6, AFB 26.4, DFB 21.7, AF 7.6.

Fins: Origin of anal fin behind middle of base of dorsal fin. Pectoral fins reaching just beyond PO₃ with weak and flexible rays. Adipose fin above end of anal-fin base.

Luminous Organs: PLO 1–2 photophore diameters below lateral line (1 diameter in holotype). PO₄ approximately on level of PVO₂ and above, or more frequently slightly behind, vertical from PO₃ (PO₄ behind vertical from PO₃ in holotype). VLO 2–3 photophore diameters below lateral line (VLO 2art diameters below in holotype); its distance to lateral line equal to or greater than distance of PLO to lateral line. SAO₂ midway between VO₄ and AOa₁, exact position variable, but frequently closer to AOa₁, (SAO₂ closer to VO₄ in holotype). AOp₁ at or behind end of anal-fin base (AOp₁, slightly behind end of base in holotype). Pre separate from AOp; Prc1₂ on horizontal line; Prc₃4 on vertical or nearly vertical line, more than 1 photophore diameter behind vertical from Prc₂ (Prc₄ slightly behind vertical from Prc₃, 2 photophore diameters behind vertical from Prc₂ in holotype). Supracaudal and infracaudal luminous glands well developed, infrequently having single separated luminous scale preceding solid infracaudal gland. No secondary photophores found.

FIGURE 14.—Nannobrachium bristori, new species. Drawing of holotype, 110 mm, SIO 71-301, Pacific Ocean, 27°26.6′N, 155°24.6′W. (Scale bar = 1 cm.)

Size: Nannobrachium bristori is a large-bodied species, reaching a maximum size in excess of 140 mm. The largest specimen encountered was 142 mm.

Material: 98 (16–126 mm) specimens were examined, excluding type material.

DISCUSSION.—This species has been confused with N. nigrum in the past, but it is clearly a distinct species of the Regale group. Of the species in the Regale group, N. bristori has the highest VLO. In this, it is reminiscent of the species in the Nigrum group, although the VLO in that group is always considerably higher. In addition, although the pectoral fin of N. bristori is rather short, with somewhat weak and flexible rays, it is stronger and longer than in any of the Nigrum group species and does not seem to show a tendency to point downward in large specimens. Both the VLO position and condition of the pectoral fin in N. bristori, however, suggest possible affinities to species of the Nigrum group. In addition, on the graph plotted for the discriminant function analysis (Figure 3), the data points for N. bristori lie far to the left, in the midst of data points for the Nigrum group species, indicating morphological similarities with those species. For these reasons, the characteristics of N. bristori have been included in Table A–1 for comparison with the species of the Nigrum group, as well as in Table A9, the Regale group.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium bristori appears to be restricted to the tropical and subtropical waters of the North Pacific (Figure 10). It does not seem to be a particularly abundant species. Most collections contain only one or a few specimens.

No significant geographic variation could be found in N. bristori, however, the gill-raker count appears to exhibit higher variance than other species of Nannobrachium, but the cause of this variation is unclear.

ETYMOLOGY.—Named for my good friend, the late William B. Bristor, Jr., of Washington, D.C.

TABLE 12.—Measurements of Nannobrachium bristori as thousandths of standard length with notes on allometry.

FIGURE 15.—Nannobrachium cuprarium (Tåning, 1928). Drawing of 67.5 mm specimen, USNM 253150, Atlantic Ocean, 32°09′N, 64°11′W. (Scale bar= 1 cm.)

The Cuprarium Groupa

All species in this group share the unique character of dense black pigmentation on the posterior tips of both the supracaudal and infracaudal luminous glands. The pigmentation looks like a black “hood” or “cap” and somewhat resembles the caudal gland pigmentation of some species in the genera Taaningichthys and Lampadena. The pigmentation in the species of the Cuprarium group, however, is more weakly developed, and the structure appears to be more fragile than in those genera. Consequently, it may be missing in damaged specimens.

Pectoral-fin length in the species of this group is intermediate. The pectoral fins are longer than one-half the distance from the pectoral-fin base to the pelvic-fin insertion, but they never reach the pelvic-fin insertion. The pectoral rays resemble those of the Regale group species, but coincident with the slightly shorter fin length, the rays are proportionally thinner and more flexible.

Other shared characters not unique to this group include (1) VLO usually touching lateral line, (2) posterior position of SAO₁ above the VO₃4, interspace, usually at a slightly lower level than SAO₂, (3) Prc₃ on a vertical midway between Prc₂ and Prc₄, and (4) Pol₂ usually well forward of vertical from adipose fin origin.

These and other characters are compared in Table 1 for all species groups of Nannobrachium.

The Cuprarium group contains two species: Nannobrachium cuprarium (Tåning, 1928) and N. lineatum (Tåning, 1928).

Modal characters of all species in the Cuprarium group are listed in Table A10 along with those for N. isaacsi, the only species in the Isaacsi group.

Nannobrachium cuprarium (Tåning, 1928), new combination

FIGURE 15, TABLE 13

Lampanyctus cuprarius Tåning, 1928:68 [original description, North Atlantic],—Parr, 1928:88, 106–108 [key, western Atlantic, description, figure],—Bolin, 1959:33–34 [discussion, distribution].—Backus et al., 1965:144 [western Atlantic],—Bullis and Thompson, 1965:28 [northern Gulf of Mexico].—Bekker, 1967a:116-ll7 [distribution].—Backus et al., 1969:95 [western Sargasso Sea],—Nafpaktitis and Nafpaktitis, 1969:42 [discussion, figure of lectotype].—Badcock, 1970:1039 [off Canary Islands].—Gibbs and Roper, 1971:129 [diurnal vertical migration].—Gibbs et al., 1971:43, 103-104 [key, vertical distribution near Bermuda, figure].—Krefft and Bekker, 1973:87 [biology, synonymy].—Nafpaktitis, 1973:41 [redescription, figure and designation of lectotype].—Briggs, 1974:328 [tropical Atlantic endemic].—Merrett and Roe, 1974:117, 119–125 [depth and feeding habits].—Nielson, 1974:38 [listing of lectotype].—Parin et al., 1974:106–107 [in part?] [southwest Atlantic].—Roe, 1974:107, 110 [vertical migration].—Bekker et al, 1975:314 [distribution, Caribbean Sea],—Badcock and Merrett, 1976:42–43, 45 [depth].—Brooks 1976:569, 575, 581 [swimbladder size].—Nafpaktitis et al, 1977:197–199 [description, distribution, figure].—Backus et al, 1977:267, 275, 277 [zoogeography].—Paxton, 1979:14 [lectotype].—Hulley, 1981:193–195 [description, Atlantic distribution]; 1984b: 462 [description, northeast Atlantic distribution].—Moser et al, 1984:239 [relationships, larval description],—Hulley and Krefft, 1985:36–37, 42–46 [North Atlantic zoogeography].—Karnella, 1987:52, 107–110, 149–159, 163–165 [ecology and biology near Bermuda],—Gartner et al, 1987:86, 88–89, 91, 95 [eastern Gulf of Mexico].

Lampanyctus (Lampanyctus) cuprarius.—Fraser-Bruner, 1949:1086 [illustrated key].—Bekker, 1983:87, 89, 193, 200, 201 [key, description, distribution].

TABLE 13.—Measurements of Nannobrachium cuprarium as thousandths of standard length with notes on allometry.

FIGURE 16.—Distributions and localities for material examined for N. cuprarium, N. lineatum, and N. isaacsi. The closer spacing of lines represents data from relatively more abundant catches.

COMPARATIVE DIAGNOSIS.—Nannobrachium cuprarium (Figure 15) can be distinguished from N. lineatum by its fewer AO photophores, lateral line organs, and vertebrae (Table A10). In addition, its caudal peduncle is shorter than the upper-jaw length (longer than the upper jaw in N. lineatum), and Prc₃ lies on a line connecting Prc₂ and Prc₄ (but is below that line in N. lineatum). Nannobrachium cuprarium can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 25 specimens from the Atlantic Ocean and are given in Tables A2–A8 and Table A10.

Proportions: Given in Table 13.

Fins: Origin of anal fin before vertical from middle of base of dorsal fin. Pectoral fin not reaching vertical from PO₄, its rays rather weak, flexible. Adipose fin above or slightly before end of anal-fin base.

Luminous Organs: PLO art–2 photophore diameters below lateral line. PO₄ slightly higher than level of PVO₂, above and usually behind vertical from PO₃. VLO not more than its diameter below, frequently nearly touching, lateral line. SAO₂ approximately above AOa₁, AOa₁, somewhat depressed; AOa1–2 interspace enlarged. AOp₁, at or near end of anal-fin base. Pol₂ well before vertical from origin of adipose fin. Pre continuous with AOp; Prc2–3–4 on straight line at angle of about 110° to line connecting Prc1–2. Supracaudal and infracaudal luminous scales well developed, very rarely single separated scale before infracaudal gland; prominent covering of black pigment on posterior tips of infracaudal and supracaudal glands resembling hood or cap. Solitary minute secondary photophores in horizontal rows, one such photophore on each posterior margin of at least some enlarged lateral line scales and on at least some scales below lateral line on anterior part of body; rows of minute photophores between rays of caudal fin.

Size: This appears to be a small-bodied species of Nannobrachium, seldom longer than 80 mm. The largest specimen examined here was 79 mm. Bekker (1967a) reported individuals as large as 92.7 mm, whereas Parin et al. (1974) reported one of 128 mm from the southwest Atlantic, and Kotthaus (1972a) reported one sample with a specimen of 110 mm. Gibbs et al. (1971) found the maximum size of the N. cuprarium collected in the Bermuda Ocean Acre study to be 79 mm, whereas Nafpaktitis et al. (1977) reported gravid females 70–75 mm. Hulley (pers. comm., 1980) examined 28 specimens from collections made by the Walther Herwig in the South Atlantic. Although his largest specimen was a 78 mm female, he judged it was not fully mature because the eggs lacked oil droplets, and he suggested that maximum size for the species might be about 90 mm. Given these recurrent findings (that virtually all specimens of N. cuprarium are approximately 80 mm or less), it may be that those larger specimens listed by Parin et al. (1974) and Kotthaus (1972a) are misidentifications.

Material: 534 (14–78 mm) specimens were examined, including the lectotype, a 63 mm female, ZMUC P2330213, Dana sta 1231 I, 24°30′N, 80°00′W, 6 February 1922 (Nafpaktitis, 1973).

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium cuprarium is restricted to the Atlantic Ocean (Figure 16), where it is a bipolar, subtropical species. It is reported to occur during the day at 600–1200 m near Bermuda and at 700–900 m near the Canary Islands and during the night at shallower depths at both locations (Nafpaktitis et al., 1977). Kamella (1987) reported similar depth distributions in Ocean Acre material near Bermuda but with a maximum depth to 1500 meters in late summer. No consistent variations could be detected in specimens examined from the eastern and western North Atlantic, Gulf of Mexico, or South Atlantic.

Nannobrachium lineatum (Tåning, 1928), new combination

FIGURE 17, TABLE 14

Lampanyctus lineatus Tåning, 1928:68 [original description, North Atlantic].—Parr, 1928:88, 108–110 [key, western Atlantic, description, figure].—Bolin, 1959:34 [discussion, distribution],—Backus et al, 1965:144 [western Atlantic].—Bekker 1967a: 117 [equatorial Atlantic],—Backus et al, 1969:95 [western Sargasso Sea],—Nafpaktitis and Nafpaktitis, 1969:41–42 [tropical Indian, description, figure].—Badcock, 1970:1039 [off Canary Islands],—Gibbs et al, 1971:43, 107 [key, vertical distribution near Bermuda, figure],—Krefft and Bekker, 1973:188–189 [biology, synonymy].—Nafpaktitis, 1973: 40 [redescription, figure and designation of lectotype],—Nielson, 1974:38 [listing of lectotype],—Bekker et al, 1975:314 [distribution, Caribbean Sea and Gulf of Mexico].—Badcock and Merrett, 1976:42 [30°N, 23°W].—Brooks, 1976:570, 575, 581 [swimbladder size].—Parin and Golovan, 1976:262 [off West Africa].—Backus et al, 1977:267, 275, 277 [zoogeography].—Nafpaktitis et al, 1977:199–201 [description, distribution, figure].—Parin et al, 1977:122, 123 [tropical Pacific] [in part?].—Parin et al, 1978:175 [eastern tropical Atlantic].—Paxton, 1979:14 [lectotype].—Hulley, 1981:206–208 [description, Atlantic distribution]; 1984b:464 [description, northeast Atlantic distribution]; 1986b:236, 242, 245 [zoogeography, Benguela region]; 1986c:308, fig. 86.80 [description, South Africa, figure].—Gloerfelt-Tarp and Kailola, 1984:77 [illustration from Nafpaktitis and Nafpaktitis].—Moser et al, 1984:239 [relationships, larval description].—Hulley and Krefft, 1985:35, 43–46 [North Atlantic zoogeography].—Rubies, 1985:578, 584 [Valdivia Bank off Namibia; gill raker count].—Clarke, 1987:66–67 [biogeography in central Pacific, listed as c.f. lineatus].—Gartner et al, 1987:86, 88, 91, 95 [eastern Gulf of Mexico].—Karnella, 1987:52, 112 [ecology and biology near Bermuda].

Lampanyctus (Lampanyctus) lineatus.—Fraser-Brunner, 1949:1086 [illustrated key].—Bekker, 1983:87, 89, 201, 202 [key, description, distribution].

Lampanyctus niger.—Parin et al., 1977:122, 123 [?in part] [western Pacific].—[Not Günther, 1887.]

FIGURE 17.—Nannobrachium lineatum (Taning, 1928). Drawing of 157 mm specimen, USNM 298184, Atlantic Ocean, 32°09′N, 64°11′w. (Scale bar=1 cm.)

COMPARATIVE DIAGNOSIS.—Nannobrachium lineatum (Figure 17) can be distinguished from N. cuprarium by its higher number of AO photophores, lateral line organs, and vertebrae (Table A10). In addition, its caudal peduncle is longer than the upper-jaw length (shorter than the upper jaw in N. cuprarium), and the Prc₃ lies below a line connecting Prc₂ and Prc₄ (on that line in N. cuprarium). Nannobrachium lineatum can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 29 specimens from the Atlantic and up to 22 specimens from the Indo-Pacific and are given in Tables A2–A8, A10.

Proportions: Given in Table 14, for Atlantic material only.

Fins: Origin of anal fin under middle of base of dorsal fin. Pectoral fin not reaching vertical from PO₄, its rays rather weak, flexible. Adipose fin above end of anal-fin base.

Luminous Organs: PLO art–2 photophore diameters below lateral line. PO₄ slightly higher than level of PVO₂ and approximately above PO₃ or slightly behind vertical from PO₃. VLO not more than one photophore diameter below, frequently touching, lateral line. SAO₂ slightly before vertical from AOa₁-AOa₁ slightly depressed; AOa1–2 interspace sometimes enlarged. AOp₁ above end of anal-fin base. Pol₂ well before vertical from origin of adipose fin. Prc1–3 forming gentle curve; Prc₄ at lateral line with Prc₃ midway between Prc₂ and Prc₄ but below line connecting them. Supracaudal and infracaudal luminous scales well developed; frequently one, rarely two, separate scales before infracaudal gland; rather inconspicuous covering of black pigment on posterior tips of infracaudal and supracaudal glands, resembling hood or cap; black pigment least developed in some Indo-Pacific specimens. Rows of minute photophores between rays of caudal fin.

Size: Nannobrachium lineatum appears to be the largest bodied species of Nannobrachium, reaching a maximum size well in excess of 200 mm in the Atlantic but apparently not so large in the Indo-Pacific. The largest specimen examined in this study was 237 mm. Nafpaktitis et al. (1977) reported a size of over 235 mm, with three gravid females 171–237 mm. Hulley (pers. comm., 1980) reported a maximum size of 221 mm for 157 specimens from the North and South Atlantic. Gibbs et al. (1971) found the maximum size in the Bermuda Ocean Acre material to be 161 mm. From those few specimens available, it appears that Indo-Pacific forms referable to this species do not reach such a large size. The largest specimens reported by Nafpaktitis and Nafpaktitis (1969) among their material from the Indian Ocean was 97 mm. The largest specimen from the Indo-Pacific examined in this study was 122 mm.

TABLE 14.—Measurements of Nannobrachium lineatum as thousandths of standard length with notes on allometry (for Atlantic material only).

FIGURE 18.—Nannobrachium achirus (Andriashev, 1962). Drawing of 109 mm specimen, LACM 11488, Pacific Ocean, 63°01′S, 102°01.3′W. (Scale bar=1 cm.)

Material: 203 (26–237 mm) specimens were examined, including the lectotype, a male, 121.5 mm, ZMUC P2330212, Dana sta 1186 I, 17°54′N. 65°54′W. 30 November 1921 (Nafpaktitis, 1973).

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium lineatum is an uncommon species (Nafpaktitis et al., 1977), never particularly abundant. Most collections examined contained only one or a few specimens. It appears to have a tropical to subtropical distribution (Figure 16). In analyzing the Walther Herwig collections, Hulley (1981) found that N. lineatum was much more abundant in the collections between 9°N and 10°S, indicating a tropical distribution. It occurs at reported daytime depths of 700–1150 m (Nafpaktitis et al., 1977). Nighttime depths appear bimodal, as shallow as 65–350 m and as deep as 900–1000 m, indicating both migrants and non-migrants. Karnella (1987) reported similar ranges for Ocean Acre material from near Bermuda.

No consistent variation was apparent between North and South Atlantic specimens of N. lineatum, but there are considerable differences between Atlantic and Indo-Pacific material. These are manifested largely in a greater range of lateral line organ and vertebral counts, and to a lesser extent, gill raker counts (Table A10), suggesting that more than one species may be present. An attempt was made to analyze the differences between the Atlantic and Indo-Pacific specimens but was inhibited by the lack of adequate material. Until material of adequate quantity and quality becomes available, it seems best at this time to treat all forms as N. lineatum. (See also discussion of Fujii's two specimens of “Lampanyctus nigrum” from near the Ogasawara Islands in the western Pacific under N. nigrum).

The Achirus Group

The unique character distinguishing all species in this group is the nature of the extremely reduced pectoral-fin development. In all species, at a size that varies with each species, the pectoral-fin development slows or stops, usually resulting in no pectoral fins being visible in adults. The time at which this shift in growth rate occurs ranges from postlarval transformation (in N. hawaiiensis) to full adult, i.e., the change had not been completed in the largest specimens examined (90–100 mm) in N. crypticum, with the vestigial pectoral rays still visible.

From the examination of specimens in those species in which the change occurs at a larger size, it is clear that the nature of this change is unique to the species of this group. When the pectoral fin stops growing, the rays do not get longer but they do steadily thicken and become stiffer ontogenetically. The pectoral fin tends to point directly ventrally as the rays become broader, like flattened bones, and eventually anastomose along the edge of the scapula. Skin develops and thickens over the now-vestigial pectoral fin so that no trace of a pectoral fin is externally visible in large adults (except in N. crypticum). It also appears that in these species, fusion of bony rays continues with growth so that in the largest adults, no trace of the pectoral fin may be present, even upon dissection of the pectoral region (except in N. crypticum, of course).

Other shared characters useful in distinguishing, but not unique to, the species of the Achirus group include (1) SAO₁ over VO₂_₃ interspace, (2) Prc₃ directly below or slightly behind vertical from Prc₄, (3) Pol₂ usually before vertical from origin of adipose fin, and (4) PVO₁-PVO₂ distance greater than in other species groups, usually about art to art Vfe the PVO₁-PLO distance.

These and other characters are compared in Table 1 for all the species groups of Nannobrachium.

The Achirus group contains five species: N. achirus (Andriashev, 1962); N. phyllisae, new species; N. hawaiiensis, new species; N. wisneri, new species; and N. crypticum, new species.

Modal characters of all species in the Achirus group are listed in Table A11.

TABLE 15.—Measurements of Nannobrachium achirus as thousandths of standard length with notes on allometry.

Nannobrachium achirus (Andriashev, 1962), new combination

FIGURE 18, TABLE 15

Lampanyctus ater.—Norman, 1930:331 [subantarctic South Atlantic].—[Not Tåning, 1928.]

Lampanyctus achirus Andriashev, 1962:256–259 [original description, subantarctic South Pacific].—Bekker, 1964:474 [in part?] [zoogeography]; 1967a: 116 [in part?] [southwest Atlantic].—Bussing, 1965:203–204 [in part?] [geographical variability].—Nafpaktitis and Nafpaktitis, 1969:45–46 [in part] [description, South Indian],—Parin and Andriashev, 1972:885 [zoogeographic relationships].—Krefft, 1974:252 [?in part] [distribution characterized].—Parin et al., 1974:106 [in part?] [southwest Atlantic].—Wisner, 1976:176–180 [in part] [description, distribution, figure].—Paxton, 1979:14 [holotype and paratypes].—Hulley, 1981:182–184 [description, South Atlantic]; 1984a:61, 78–79, fig. 11 [description, off South Africa]; 1986b:240, 242 [zoogeography]; 1986c:306, fig. 86.73 [description, South Africa, figure]; 1989:53 [South Indian, 38°09′39″S, 78°02′63″E]; 1990:162, 163 [figured, Southern Ocean].—McGinnis, 1982:42–44, 66–70 [in part?] [distribution south of 30°S, relationships, zoogeography].—[?] Moser et al., 1984: 238239, fig. 124E [relationships, larva figured from Moser and Ahlstrom, 1974].—Paxton and Hanley, 1989:263 [?in part] [Australian distribution].—Paxton et al., 1995:1315 [listed] [not seen, fide J. Paxton].

Lampanyctus sp. [possibly achirus].—Moser and Ahlstrom, 1974:406–407 [larva figured].

Lampanyctus (Lampanyctus) achirus.—Bekker, 1983:86, 87, 198, 199 [in part] [key, description, distribution].

COMPARATIVE DIAGNOSIS.—Nannobrachium achirus (Figure 18) can be distinguished from all other species in the Achirus group by its higher number of gill rakers and tooth patches on the lower limb of the second gill arch, and from all other species, except N. wisneri, by its higher number of AO photophores, infracaudal luminous gland scales, lateral line organs, and vertebrae (Table A11). It also can be separated from N. wisneri and N. hawaiiensis by the visible presence of pectoral fins in small specimens (up to about 60 mm). Nannobrachium achirus can be distinguished from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 78 specimens and are given in Tables A2–A8, A11.

Proportions: Given in Table 15.

Fins: Origin of anal fin behind vertical from middle of base of dorsal fin. Pectoral fins relatively long and well developed in juvenile stages (easily visible in specimens up to about 60 mm), reaching more than one-half distance to pelvic-fin insertion, progressively becoming relatively shorter, with thicker rays, and covered by skin (in various stages of becoming vestigial between about 50–80 mm). Adults (longer than about 80 mm) with vestigial rays buried in skin and not externally visible unless skin abraded or otherwise torn. In largest adults, vestigial pectoral-fin elements cannot be found (perhaps lost through resorption). Adipose fin over end of anal-fin base.

Luminous Organs: PLO about 2 photophore diameters below lateral line. PO₄ approximately on level of PVO₂ and above PO₃. PVO₁_₂ interspace wide, that distance 2–3 times into PVO₂-PLO distance. SAO₁ above VO₂_₃ interspace, frequently closer to VO₃. SAO₂ midway above interspace between VO₄ and AOa₁. SAO₃ above AOa₁ but somewhat variable in position. AOa₁ slightly depressed; AOa₁_₂ interspace not visibly enlarged. AOp₁ above or behind end of anal-fin base. Prc separate from AOp; Prc₁_₂ on horizontal line; Prc₃ below Prc₄ but slightly in advance of vertical from center of Prc₄. Supracaudal and infracaudal luminous glands well developed, commonly having single separate luminous scale preceding solid infracaudal gland. Secondary photophores in single row on either side of back; single photophore on posterior edge of each scale in first full scale row below middle row of scales; best developed and most prominent in region of adipose fin and less well developed further forward but appear to extend forward to nape.

Size: Nannobrachium achirus is a large-bodied species, reaching a maximum size in excess of 160 mm. The largest specimen recorded by Hulley (pers. comm., 1980) from the South Atlantic was 162 mm. The largest specimen examined in this study was 154 mm.

FIGURE 19.—Distributions and localities for material examined for species of the Achirus Group.

FIGURE 20.—Nannobrachium phyllisae, new species. Drawing of holotype, 108 mm, MCZ 96457, Pacific Ocean, 33°24′S, 73°33′W to 33°32′S, 73°35′W. (Scale bar= 1 cm.)

Material: 451 (30–154 mm) specimens were examined, including the holotype, 124 mm, ZIN 36111, R/V Ob, sta 409, 64°36′S, 108°52′W, 24 April 1958, 1000 m.

DISCUSSION.—Within this species, the only one of the Achirus group previously described, there is the possibility of two sibling species, one having slightly more gill rakers than the other, as has been noted by Hulley (1981; and pers. comm., 1980). Based on material from the Patagonian Shelf off South America, as well as two specimens from the central South Atlantic, there appear to be two forms with different gill raker counts (one, typically 5+12/13, the other 6+13/14). These are obviously very close, but several additional differentiating characters were noted. In general, the more-numerous-gill-raker form tended to be black or gray in color versus brown or tan, had a larger vomerine tooth patch, and had the SAO₃ farther back. These characters, however, were not always correlated. Specimens were frequently found with a mixture of these characters, to the extent of having characters of each form on opposite sides of the same fish. Further analysis failed to establish consistent differences. Consequently, it is necessary to recognize only one species and to ascribe observed differences to a kind of mosaic pattern of variability.

The paratype listed by Andriashev (1962) as having been taken along with the holotype was not in the collections of the Zoological Institute, Russian Academy of Sciences, St. Petersburg, nor was any mention made of the disposition of the specimen in the original description. Checking the records further, Andriashev (pers. comm., 1976) found that the specimen had been sent (apparently on permanent loan) to Rolf Bolin at the Hopkins Marine Station (Stanford University) at the time the species was described. The specimen is now permanently in the California Academy of Sciences Fish Collection, Pacific Grove, California, CAS 15646.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium achirus is a circumglobal, deep-water, subantarctic species (Figure 19). Because it has such a broad distribution, special efforts were made to compare material from the Atlantic, Pacific, and Indian sections of the Southern Ocean, but no patterns of differences were found in the specimens examined.

Nannobrachium phyllisae, new species

FIGURE 20, TABLE 16

Lampanyctus achirus.—Bussing, 1965:203–204 [in part] [midwaters of Peru-Chile Trench].—Craddock and Mead, 1970:28 [in part] [southeast Pacific].—Parin, 1971:82, 87, 89, 90 [in part?] [Peru Current].—Parin et al., 1973:114, 115 [?in part] [eastern tropical Pacific].—Wisner, 1976:177–180 [in part] [discussion, fig. 166A],—[Not Andriashev, 1962.]

TYPE SPECIMENS.—Holotype: Male, 108 mm, WHOI, Anton Bruun Cruise XIII, sta 52, 33°24′S, 73°33′W to 33°32′S, 73°35′W, 01 February 1966.

Paratypes: SIO 52–372, 2 (83–92 mm); SIO 63–1013, 2 (74–88 mm); SIO 63–1014, 1 (65 mm); SIO 65–667, 4 (112–147 mm); SIO 68–320, 1 (85 mm); SIO 69–321, 1 (28 mm); SIO 69–330, 7 (26–84 mm); USNM 303164, 3 (31–35 mm); USNM 303310, 5 (97–149 mm); WHOI 1344, 1 (39 mm); WHOI 1359, 1 (126 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium phyllisae (Figure 20) can be distinguished from N. achirus by its lower number of AO photophores, gill rakers, tooth patches, infracaudal luminous gland scales, lateral line organs, and vertebrae (Table A11); however, in all characters, there is overlap in ranges of counts. Similar differences are found between N. phyllisae and N. wisneri, namely, N. phyllisae has a lower number of infracaudal luminous glands and fewer vertebrae but has one more gill raker on the upper limb of the first gill arch. Nannobrachium phyllisae, however, can be separated from both N. wisneri and N. hawaiiensis by the presence of pectoral fins in small specimens (up to about 50 mm). It can be further separated from N. hawaiiensis, as well as from N. crypticum, by its higher AO photophore, gill raker, lateral line organ, and vertebral counts. It can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 21 specimens from the eastern Pacific Ocean and are given in Tables A2–A8, A11. Counts for the holotype are D 16, A 20, P₁ none, GR 4+12, tooth patches 9, AO 7+7, SC/IC 3/i+5, LL 34, V 15+21.

TABLE 16.—Measurements of Nannobrachium phyllisae as thousandths of standard length with notes on allometry.

Proportions: Given in Table 16. Holotype measurements as follows: SL 108, AD 18.6, PDD 19.5, CPD 11.4, CPL 21.6, PADL 20.5, PDL 53.5, PPL 41.4, PANL 56.2, PAL 12.9, HL 31.4, UJL 22.7, SOL 5.0, ED 5.2, SGL 5.3, IGS 12.1, IGEL 13.9, AFB 28.7, DFB 21.7, AF 8.7.

Fins: Origin of anal fin under middle of dorsal-fin base. Pectoral fins relatively long and well developed in juvenile stages (easily visible in specimens up to about 50 mm), progressively becoming relatively shorter, with thicker rays, (covered by skin in various stages of becoming vestigial, between about 40–70 mm); vestigial rays buried in skin and not externally visible. Largest adults with vestigial pectoral-fin elements undetectable (perhaps lost through resorption). Adipose fin over end of anal-fin base.

Luminous Organs: PLO 1–2 photophore diameters below lateral line (slightly more than 1 in holotype). PO₄ on level of PVO₂ (above level in holotype) and above PO₃. PVO1–2 interspace wide, that distance 2–3 times into PVO₂-PLO distance (about 2art times in holotype). SAO₁ above VO2–3 interspace (slightly closer to VO₂ in holotype) SAO₂ above VO₄-AOa₁ interspace but usually closer to AO₁ (notably closer to AOa₁ in holotype). SAO₃ behind vertical from AOa₁. AOa₁ not noticeably depressed; AOa1–2 interspace only very slightly enlarged, if at all. AOp₁ above end of anal-fin base (slightly behind end in holotype). Pre slightly separate from AOp; Prc1–2 on horizontal line; Prc₃ below Prc₄ but variable, although frequently behind vertical from Prc₄ (Prc₃ on vertical from posterior margin of Prc₄ in holotype). Supracaudal and infracaudal luminous glands well developed, commonly having single separated luminous scale preceding solid infracaudal gland. Secondary photophores not found.

Size: Nannobrachium phyllisae is a large species, reaching a maximum size of at least 151 mm based on examined material. Wisner (1976), in discussing the Lampanyctus achirus species complex, listed a maximum size of about 155 mm for specimens from the southeast Pacific, which probably included this species.

Material: 30 (28–151 mm) specimens, excluding type material.

DISCUSSION.—In the past, N. phyllisae has been confused with N. achirus and frequently included in discussions of that species (Bussing, 1965; Craddock and Mead, 1970; and Wisner, 1976). There is no doubt that N. phyllisae is most closely related to N. achirus, which it resembles in size at which loss of pectoral fins occurs, in general body size and shape, and in having similar meristics. Because of the similarity of these two species, N. phyllisae may be expected to have similar larvae and to show other characteristics that have been noted for N. achirus, including secondary photophores on the back.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium phyllisae is restricted to the Peru-Chile Current area of the southeastern Pacific Ocean (Figure 19). As might be expected for a species with such a restricted geographic range, no consistent geographic variability was found in specimens examined from different parts of the range.

ETYMOLOGY.—I have the pleasure of naming this species in honor of my former wife Phyllis E. Fabian, as a token of recognition for her many years of support, which culminated in this study.

Nannobrachium hawaiiensis, new species

FIGURE 21, TABLE 17

Lampanyctus sp. (no pectorals).—Berry and Perkins, 1966:662 [Pacific off California and northern Mexico].

FIGURE 21.—Nannobrachium hawaiiensis, new species. Drawing of holotype, 63 mm, SIO 71-300, Pacific Ocean, 27°24.5′-27°24.9′N, 155°25.5′-155°13.7′W. (Scale bar=1 cm.)

Lampanyctus niger (Form A).—Clarke, 1973:416–418 [ecology north of Hawaii].—[Not Günther, 1887.]

Lampanyctus achirus Species Complex “northern Pacific” form.—Wisner, 1976:177–180, fig. 166B [in part?] [size, characterization].—[Not Andriashev, 1962.]

Lampanyctus niger.—Parin et al., 1977:122, 123 [in part?] [western Pacific].—[Not Günther, 1887.]

Lampanyctus “lacks pectorals” (sp. nov. A).—Loeb, 1979a: 178, 186 [in part?] [larvae, central North Pacific]; 1979b:780–782, 783 [in part?] [larval depth distribution]; 1980:192–195, 199 [in part?] [central Pacific larval distribution].

Lampanyctus (sp. 1).—Fujii, 1984:69, pl. 66-N [description, distribution].

Lampanyctus sp.—Moser et al., 1984:238, fig. 124F.

Lampanyctus (sp. A).—Clarke, 1987:63, 65 [biogeography in central Pacific].

Nannobrachium “no pectorals”.—Moser and Ahlstrom, 1996:420–421 [early life history and larvae illustrated].

TYPE SPECIMENS.—Holotype: Male, 63 mm, SIO 71-300, Aries Expedition, sta 9, 27°24.5′N, 155°25.5′W to 27°24.9′N, 155°13.7′W, 30 September 1971.

Paratypes: HIMB 70–1221, 76 (28–70 mm); HIMB 71-22, 18 (34–70 mm); HIMB 71-617, 32 (35–60 mm); HIMB 71-618, 62 (22–70 mm); HIMB 71-622, 22 (21–62 mm); HIMB 71-631, 30 (36–69 mm); LACM 30–988, 1 (72 mm); LACM 92–6216, 1 (57 mm); OS 012814, 5 (28–68 mm); SIO 71-300, 3 (14–69 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium hawaiiensis (Figure 21) can be distinguished from all species in the Achirus group, except N. crypticum, by its lower number of AO photophores, infracaudal luminous gland scales, lateral line organs, and vertebrae (Table A11). It can be separated from N. achirus and N. phyllisae by its lower number of gill rakers and tooth patches on the lower limb of the second gill arch. It can be distinguished from all species, especially from N. crypticum, by the complete absence of pectoral fins through the juvenile and adult states. It also can be separated from N. crypticum by its higher number of gill rakers and tooth patches on the lower limb of the second gill arch. Nannobrachium hawaiiensis can be separated from all other species of Nannobrachium by the combination of characters in Table 1, but especially by the absence of pectoral fins.

DESCRIPTION.—Counts are based on up to 26 specimens and are given in Tables A2–A8, A11. Counts for the holotype are D 14, A 16, P₁ none, GR 4+11, tooth patches 9, AO 5+7, SC/IC art, LL 33, V 15+20.

TABLE 17.—Measurements of Nannobrachium hawaiiensis as thousandths of standard length with notes on allometry.

FIGURE 22.—Nannobrachium wisneri, new species. Drawing of holotype, 63 mm, MCZ 55478, Atlantic Ocean, 35°50′S, 2°16′W. (Scale bar= 1 cm.)

Proportions: Given in Table 17. Holotype measurements (in mm) as follows: SL 63, HD 10.2, PDD 10.1, CPD 4.8, CPL 14.0, PADL 10.4, PDL 30.6, PPl 24.5, PANL 33.3, PAL 8.6, HL 18.0, UJL 13.6, SOL 2.7, ED 4.7, SGL 3.3, IGS 4.9, IGEL 4.9, AFB 13.7, DFB 11.2, AF 5.6.

Fins: Origin of anal fin below middle of base of dorsal fin. Pectoral fins completely lacking in juvenile, subadult, and adult stages, apparently lost at about time of postlarval transformation. Larvae with enormous, fan-shaped pectorals (Moser and Ahlstrom, 1996:421, figure Myctophidae 17). Pectoral-fin rays present buried in the skin in small juveniles (approximately 25–35 mm). Adipose-fin base over end of anal-fin base.

Luminous Organs: PLO about 2 photophore diameters below lateral line. PO₄ approximately on, or slightly below, level of PVO₂ (about on level of PVO₂ in holotype) and above PO₃. PVO1–2 interspace wide, that distance 2–3 times into PVO₂-PLO distance (slightly more than 2 times in holotype). SAO₁ approximately over VO₃ (behind vertical from VO₃ in holotype). SAO₂ above interspace between VO₄ and AOa₁ but much closer to AOa₁, sometimes over AOa₁ (SAO₂ before vertical from AOa₁ in holotype). SAO₃ behind vertical from AOa₁. AOa₁ not noticeably depressed nor AOa1–2 interspace noticeably enlarged. AOp₁ above end of anal-fin base. Prc slightly separate from AOp (notably separate in holotype); Prc1–2 approximately on horizontal line; Prc₃ below Prc₄ but slightly before vertical from center of Prc₄. Supracaudal and infracaudal luminous glands well developed, rarely having single separate luminous scale preceding solid infracaudal gland. Secondary photophores possibly present.

Size: Nannobrachium hawaiiensis is a small-bodied species of Nannobrachium, probably not greatly exceeding 80 mm in length. The longest specimen encountered in this study was 81 mm. Wisner (1976) gave about 70 mm as the maximum size for the “northeastern Pacific form” of the “Lampanyctus achirus Species Complex” and reported that specimens 58–65 mm had well-developed, although immature, ova.

Material: 942 (10–81 mm) specimens, excluding type material.

DISCUSSION.—For a number of years, N. hawaiiensis has been recognized as a distinct species in the North Pacific. Berry and Perkins (1966) identified the specimens that they listed as “Lampanyctus sp. (no pectorals),” pointing out that these specimens are specifically distinct from N. achirus. Wisner (1976, fig. 166B), however, discussed the very complex situation in the eastern Pacific, with an indication of clinal variation in certain meristics in specimens from the North Pacific to the southeast off South America. Indeed, the number of gill rakers and AO photophores in four of the species involved (Wisner did not identify specimens of N. crypticum with the achirus complex) generally increase monotonically from north to south, with N. hawaiiensis, the northernmost species, having the lowest numbers and N. achirus, the southernmost, having the highest numbers. Once the four species involved are distinguished, however, it is clear that there is no cline in characteristics of a single species but rather four species, each with different meristics.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium hawaiiensis is the only species of the Achirus group found exclusively in the northern hemisphere. It is restricted to the North Pacific Central water mass (Figure 19). Material was compared from the eastern and western parts of the range, but no consistent geographic variation was evident.

ETYMOLOGY.—The name refers to the Hawaiian Islands near the center of the range, where this species is abundant in the surrounding midwaters.

Nannobrachium wisneri, new species

FIGURE 22, TABLE 18

Lampanyctus ater.—Norman, 1930:331 [in part] [South Atlantic].—[Not Tåning, 1928.]

Lampanyctus intricarius.—Norman, 1930:330 [in part, fide McGinnis, 1982] [South Atlantic].—[Not Tåning, 1928.]

Lampanyctus niger.—Norman, 1930:331 [in part] [South Atlantic].—[Not Günther, 1887.]

Lampanyctus sp.—Norman, 1930:331 [South Atlantic].

Lampanyctus achirus.—Bussing, 1965:203–204 [in part] [midwaters of Peru-Chile Trench].—Nafpaktitis and Nafpaktitis, 1969:45–46 [in part] [description, South Indian, fig. 55].—Craddock and Mead, 1970:28 [in part] [southeast Pacific].—Parin, 1971:82, 87, 89, 90 [?in part?] [Peru Current].—Parin et al., 1974:106 [?in part] [southwest Atlantic].—Rubies, 1985: 578–584 [?in part?] [Valdivia Bank off Namibia, gill raker numbers].—[Not Andriashev, 1962.]

TABLE 18.—Measurements of Nannobrachium wisneri as thousandths of standard length with notes on allometry.

Lampanyctus cf. achirus.—Hulley, 1972:225 [in part?] [description, South Atlantic].—[Not Andriashev, 1962.]

Lampanyctus ?achirus.—Hulley, 1981:184–185 [description, southwest Atlantic].—[Not Andriashev, 1962.]

Lampanyctus sp. A.—McGinnis, 1982:43–45, 66 [in part?] [distribution south of 30°S, relationships, zoogeography].

Lampanyctus (Lampanyctus) achirus.—Bekker, 1983:86–87, 198–199 [in part] [key, description, distribution].—[Not Andriashev, 1962.]

Lampanyctus sp. B.—Hulley, 1986b:243 [zoogeography]; 1986c:310, fig. 86.89 [description, South Africa, figure].

TYPE SPECIMENS.—Holotype: Female (?), 57 mm, MCZ 55478 (RHB 2229), R.V. Atlantis II, sta 60, 35°50′S, 2°16′W, 23 April 1971, depth 600–650 m.

Paratypes: LACM 11-259, 7 (30–37 mm); LACM 11-273, 6 (30–85 mm); MCZ 55478 (RHB 2229), 2 (34–35 mm); SIO 58–256, 1 (64 mm); SIO 61-46, 31 (34–71 mm); SIO 63-542, 2 (37–57 mm); SIO 63-544, 2 (34–60 mm); SIO 69-321, 22 (25–69 mm); USNM 209390, 139 (20–65 mm); USNM 209395, 31 (25–65 mm); USNM 209400, 21 (38–68 mm); WHOI 13–41, 4 (43–54 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium wisneri (Figure 22) can be distinguished from N. crypticum, N. achirus, and N. phyllisae by its gill raker count (lower than in N. achirus and N. phyllisae, higher than in N. crypticum) and by the virtually complete lack of pectoral fins in specimens larger than small juvenile stages (about 35 mm). It can be most easily distinguished from N. hawaiiensis by the higher number of infracaudal luminous gland scales, lateral line organs, and vertebrae (Table A11). Nannobrachium wisneri can be separated from all other species of Nannobrachium by the combination of characters in Table 1, but especially by the virtual absence of pectoral fins.

DESCRIPTION.—Counts are based on up to 26 specimens and are given in Tables A2–A8, A11. Counts for the holotype are D 15, A 19, P₁, none, GR 4+11, tooth patches 9, AO 8+6 (L), 7+7 (R), SC/IC 4(?)/7(?), LL 36, V 15+20.

Proportions: Given in Table 18. Holotype measurements (in mm) as follows: SL 57, HD 9.1, PDD 8.1, CPD 5.1, CPL 11.1, PADL 11.0, PDL 29.2, PPL 22.9, PANL 30.3, PAL 7.9, HL 15.8, UJL 12.1, SOL 3.0, ED 4.0, SGL 3.8 (damaged), IGS 9.9, IGEL 9.9, AFB 14.6, DFB 11.9, AF 4.

Fins: Origin of anal fin under or before vertical through center of base of dorsal fin (before vertical in holotype). Pectoral fins completely lacking in subadult and adult stages; vestigial in small juveniles (less than about 30 mm). Fin rays present but buried in the skin in larger juveniles (approximately 30–35 mm). Adipose-fin base over end of anal-fin base.

Luminous Organs: PLO typically more than 2 photophore diameters below lateral line (nearly 3 diameters in holotype). PO₄ approximately on, or slightly below, level of PVO₂ and above PO₃. PVO1–2 interspace wide, that distance 1art–3 times into PVO₂-PLO interspace (about 1art times in holotype). SAO₁ above VO₃ but somewhat forward of vertical from center of VO₃. SAO₂ midway above interspace between VO₄ and AOa₁ but variable in position (closer to vertical from AOa₁ in holotype). SAO₃ above AOa₁. AOa₁ not noticeably or only slightly depressed; AOa1–2 interspace not noticeably enlarged. AOp₁ above end of anal-fin base (behind base on left side of holotype). Prc slightly separate from AOp; Prc1–2 approximately on horizontal line, but Prc₂ often slightly lower; Prc₃ below Prc₄ but slightly in advance of vertical from center of Prc₄. Supracaudal and infracaudal luminous glands well developed, rarely having single separated luminous scale preceding solid infracaudal gland. Possible traces of secondary photophores on back in similar position to those of N. achirus.

Size: Nannobrachium wisneri probably does not exceed 90 mm in length. The largest specimen examined for this study was 88 mm.

FIGURE 23.—Nannobrachium crypticum, new species, Drawing of holotype, 87 mm, HIMB TC 47-61, pacific Ocean, 3°30′N, 145°00′W. (Scale bar=1 cm).

Material: 1020 (20–83 mm) specimens, excluding type material.

DISCUSSION.—Nannobrachium wisneri has long been confused with both N. achirus and N. phyllisae. For example, Nafpaktitis and Nafpaktitis (1969), in discussing Indian Ocean myctophids, had only two specimens that they referred to “N. achirus.” The larger specimen (144 mm) was correctly identified, but the smaller specimen (63 mm, label number 7324) was actually N. wisneri. In fact, it is this specimen of N. wisneri that was illustrated in their fig. 55 as L. achirus. A different problem is an 80 mm specimen collected by the Walther Herwig (sta 348/71) in the South Atlantic and listed by Hulley (1981) as Lampanyctus? achirus. It appears to be a specimen of N. wisneri with an atypically low number of gill rakers (4+10 versus 4+11 or 12 in typical specimens of N. wisneri) and vertebrae (given as 34 by Hulley, whereas the modal number of N. wisneri is 37); however, it has 9 tooth patches on the lower limb of the second gill arch, the modal number for N. wisneri. Furthermore, in examining the specimen very carefully, no trace of pectoral-fin rays could be found, even where the skin was abraded. Thus, it seems best to consider this specimen an example of N. wisneri with an abnormally low number of gill rakers and vertebrae, despite the collection locality of Walther Herwig sta 348, which is off the mouth of the Rio de la Plata, far to the south of other specimens of N. wisneri examined from the western South Atlantic. I agree with Hulley that it may yet prove to represent a distinct species.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium wisneri is nearly circumglobal in Subtropical Convergence waters (Figure 19). The gap in its range south, and especially east, of Australia appears to be real, not an artifact of sampling effort. Particular attention was paid to comparing specimens from the Atlantic, Pacific, and Indian oceans, but no consistent meristic differences were found, except the one Atlantic specimen discussed above.

ETYMOLOGY.—It is an honor and a pleasure to name this species for Robert L. Wisner of the Scripps Institution of Oceanography in recognition of his contributions to the systematics of myctophids and other oceanic fishes.

Nannobrachium crypticum, new species

FIGURE 23, TABLE 19

Lampanyctus “niger”.—Hartmann and Clarke, 1975:637 [in part] [ecology at 39°30N′, 145°].—[Not Günther, 1887.]

Lampanyctus sp. D.—Clarke, 1987:59, 61, 62 [in part] [biogeography in central Pacific].

TYPE SPECIMENS.—Holotype: Female, 87 mm, HIMB TC 47–61, 3°30′N, 145°00′W, 8 February 1970, Thomas A. Clarke, collector.

Paratypes: HIMB 47–52, 40 (28–93 mm); HIMB 47–6, 28 (30–89 mm); HIMB 47–61, 13 (20–87 mm); HIMB 47–67, 31 (23–98 mm); SIO 52-320, 1 (41 mm); SIO 60-236, 3 (31–87 mm); SIO 73-164, 2 (87–90 mm); USNM 303313, 7 (27–61 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium crypticum (Figure 23) can be distinguished from all other species of the Achirus group by the number of AO photophores, gill rakers, and lower limb tooth patches on the second gill arch (all fewer than in any other species of the Achirus group) (Table A11), and by the presence of externally visible pectoral fins in all life stages (except perhaps in the largest adults—greater than 90 mm). Nannobrachium crypticum is superficially similar to many species in the Nigrum group, but in addition to the differences in Table 1, it can be distinguished from them by the number of gill rakers and lower limb tooth patches on the second gill arch (both lower than in N. nigrum and N. atrum; one fewer gill raker, on average, than in N. indicum), by the number of its AO photophores and vertebrae (both lower than in N. atrum and N. gibbsi), and by the number of infracaudal luminous gland scales and lateral line organs (on average, both higher than in N. indicum; fewer lateral line organs than in N. atrum) (Table A1). Nannobrachium crypticum also can be distinguished from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 99 specimens from the Pacific Ocean and are given in Tables A2–A8, A11. Counts for the holotype are D 13, A 17, P₁ 12?, GR 4+10, tooth patches 8, AO 5+6 (L), 5+7 (R), SC/IC 3/i+5, LL 32, V 15+19.

TABLE 19.—Measurements of Nannobrachium crypticum as thousandths of standard length with notes on allometry.

Proportions: Given in Table 19. Holotype measurements (in mm) as follows: SL 87, HD 14.4, PDD 12.5, CPD 6.9, CPL 19.2, PADL 18.7, PDL 39.8, PPL 34.3, PANL 47.7, PAL 13.8, HL 25.3, UJL 18.1, SOL 4.4, ED 5.0, SGL 5.3, IGS 8.5, IGEL 10.2, AFB 21.1, DFB 14.6, AF 6.4.

Fins: Origin of anal fin behind vertical through middle of base of dorsal fin. Pectoral fins not reaching beyond PO₃, pointing directly downward in larger specimens; rays progressively thicker, stiffer, and relatively shorter in larger specimens but remnants always visible externally, apparently not covered with skin even in 90–100 mm specimens. (Remnant rays in holotype are 2–3 mm long.)

Luminous Organs: PLO 1–2 photophore diameters below lateral line (1 in holotype). PO₄ approximately on level of PVO₂ (on level in holotype) but somewhat variable and above but slightly behind vertical from PO₃. PVO₂ before or above middle of pectoral-fin base (above middle in holotype); PVO1–2 interspace art–art of PVO₂–PLO distance (approximately art in holotype). VLO within 1 photophore diameter below lateral line. SAO₂ midway between VO₄ and AOa₁, often closer to AOa₁ (closer to AOa₁ in holotype). SAO₃ above, and slightly forward of vertical from AOa₁. AOa₁ slightly depressed; AOa1–2 interspace slightly enlarged. AOp₁ at end of anal-fin base. Prc separated from AOp; Prc1–2 on horizontal line; Prc3–4 on or nearly on vertical, 1 to 2 photophore diameters behind Prc₂ (Prc3–4 vertical in holotype, approximately 1 photophore diameter behind Prc₂); Prc₃ approximately equidistant between Prc₂ and Prc₄. Pol₂ approximately on vertical from adipose-fin origin. Supracaudal and infracaudal luminous glands well developed, infrequently having single separated luminous scale preceding solid infracaudal gland. Secondary photophores seen on back of 1 specimen, 1 photophore near posterior margin of each scale in 2 rows, 1 on either side of dorsal midline in region behind center of dorsal-fin base but additional extent of secondary photophores uncertain.

Size: Nannobrachium crypticum probably reaches a maximum size in excess of 100 mm. The largest specimen encountered in this study was 98 mm.

Material: 252 (19–93 mm) specimens, excluding type material.

DISCUSSION.—Just as N. nigrum and N. atrum have been confused in the past, specimens of N. crypticum have been misidentified in collections under both of those names. It was recognized, however, as related to, but distinct from, other species of Nannobrachium by Hartmann and Clarke (1975) and by Clarke (1987).

Despite the close similarity and initial confusion between N. crypticum and N. gibbsi, there is no doubt that N. crypticum belongs to the Achirus, not the Nigrum, species group. Although the Pol₂ is relatively far posterior in relation to the adipose-fin origin in this species, it is a typical Achirus group species in all other characters: Prc arrangement, wide PVO1–2 interspace, and, most importantly, the devolution of the pectoral fins as they become progressively more vestigial in larger specimens. The pattern is clearly the same in this species as in N. achirus, differing only in the larger size at which the vestigial pectoral rays would become covered with skin in N. crypticum. Because the large specimens available are in poor condition, with the skin torn, it is not clear whether N. crypticum ever has the vestigial pectoral fins completely covered over with skin as in the remaining Achirus group species. It may be that in very large specimens (probably in excess of 100 mm) without torn skin, the vestigial pectoral fins would not be visible externally.

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium crypticum is apparently restricted to the equatorial Pacific (Figure 19), where it occurs across the breadth of the ocean from east to west. Variability, which may be geographical, was noted in some meristic characters. In a sample of five specimens taken on expedition Piquero V (lot 137, SIO 69-341) in the southeast portion of the range at 13.5°S, 110.5°W, four specimens had dorsal- and anal-fin ray counts, as well as AO photophore counts, that were at the high end of the range for the species. On the other hand, another sample of six specimens from Piquero V (lot 527, SIO 69-338) taken at 9°S, 108°W, shows little indication of a higher than average number of dorsal- or anal-fin rays or AO photophores. More material is required to clarify whether this variability is significant.

FIGURE 24.—Nannobrachium isaacsi (Wisner, 1974). Drawing of 98.5 mm specimen, LACM 34917-1, Atlantic Ocean, 20°01′N, 18°15′W. (Scale bar=1 cm.)

ETYMOLOGY.—The name is derived directly from the Latin adjective crypticum, meaning “obscure” or “hidden,” alluding to the unrecognized existence and relationships of this species.

The Isaacsi Group

The unique character distinguishing the species in this group is the position of the VO₂ directly above the VO₁ instead of midway between VO₁ and VO₃ as in all the other groups.

The pectoral-fin development in this group is essentially identical to that of the species in the Cuprarium group except that the pectoral fin is usually slightly longer. Normally, the pectoral fin reaches to or nearly to the pelvic-fin insertion, and the pectoral rays are slightly thicker and stiffer than those of the Cuprarium group.

One other character shared with the species of the Cuprarium group is the position of the Prc₃; it is found approximately on a vertical midway between Prc₂ and Prc₄.

These and other characters are compared in Table 1 for all the species groups of Nannobrachium.

The Isaacsi group contains a single species: N. isaacsi (Wisner, 1974).

Modal characters for N. isaacsi are listed in Table A10 along with the species in the Cuprarium group.

Nannobrachium isaacsi (Wisner, 1974), new combination

FIGURE 24, TABLE 20

Lampanyctus micropterus Brauer, 1906 [in part] [2 of 3 syntypes, fide Hulley, 1981].

Lampanyctus isaacsi Wisner, 1974:14–17 [original description, eastern equatorial Atlantic].—Nafpaktitis et al., 1977:201–203 [description, distribution, figure].—Backus et al., 1977:267, 275, 277 [zoogeography].—Paxton, 1979: 14 [holotype and paratypes].—Hulley, 1981:204–206 [description, Atlantic distribution].—Kinzer and Schulz, 1985:314, 316 [depth distribution, central equatorial Atlantic].—Rubies, 1985:578, 584 [Benguela Current, off Namibia, gill raker number low—questionable identification].

Lampanyctus (Lampanyctus) isaacsi.—Bekker, 1983:87–89, 193, 200 [key, description, distribution].

TABLE 20.—Measurements of Nannobrachium isaacsi as thousandths of standard length with notes on allometry.

COMPARATIVE DIAGNOSIS.—Nannobrachium isaacsi (Figure 24) can be distinguished from all other species of Nannobrachium by the position of the VO₂ photophore forward above the VO₁. It can be further separated from the species of the Cuprarium group by the combination of characters in Table A10 and from all species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 25 specimens from the eastern Atlantic and are given in Tables A2–A8, A10.

Proportions: Given in Table 20.

Fins: Origin of anal fin before vertical from middle of dorsal-fin base. Pectoral fin barely reaching vertical from PO₅, its rays rather weak, flexible. Base of adipose fin above end of anal-fin base.

Luminous Organs: PLO art–1art photophore diameters below lateral line. PO₄ slightly higher than level of PVO₂ and behind vertical from PO₃. VLO usually touching lateral line. SAO₂ before vertical from AOa₁. AOa₁ slightly depressed; AOa series slightly concave downward. AOp₁ above end of anal-fin base. Pol₂ well before vertical from origin of adipose-fin base. Prc nearly continuous with AOp; Prc2–3–4 usually forming straight line at angle of about 120° with line connecting Prc1–2. Supracaudal and infracaudal scales rather weakly developed, sometimes with single separated scale preceding infracaudal gland. No secondary photophores found.

Size: Nannobrachium isaacsi apparently reaches a maximum size in excess of 130 mm. The largest specimen examined herein was 125 mm. Nafpaktitis et al. (1977) reported a maximum size of 130 mm, whereas Hulley (pers. comm., 1980) gave the maximum size as 132 mm among the 179 specimens he examined.

Material: 99 (16–125 mm) specimens were examined.

DISCUSSION.—Hulley (1981) examined Brauer's (1906) type material of Lampanyctus micropterus. It consists of three syntypes collected by the Valdivia, two from the Gulf of Guinea that “are identical with L. isaacsi in all respects” (Hulley, 1981:205). The third specimen from the Indian Ocean east of the Seychelles proved to be the same as Triphoturus microchir (Gilbert, 1913). Subsequently, Hulley (1986a) made both names junior synonyms of Triphoturus nigrescens (Brauer, 1904).

DISTRIBUTION AND GEOGRAPHIC VARIATION.—Nannobrachium isaacsi is found principally in the eastern tropical Atlantic (Figure 16), although Nafpaktitis et al. (1977) reported a few specimens from the western tropical Atlantic off eastern Brazil, which they regard as waifs. Based on the findings of Nafpaktitis et al. (1977), Hulley (1981; and pers. comm., 1980), and the material examined herein, N. isaacsi may have a disjunct distribution, with the two centers separated by a gap in the Gulf of Guinea. It is reported to occur between 550 and 750 m during the day and between 40 and 325 m at night (Nafpaktitis et al., 1977). No geographic variation was evident. As material in better condition becomes available, however, specimens from the two apparent centers of distribution should be carefully compared for possible differences.

Zoogeography of the Species of the Genus Nannobrachium

In the first comprehensive overview of marine biogeography, Ekman (1959) presented a rather coarse picture of open-ocean pelagic regions. Since then, a wide variety of investigations (see below) have added greatly to our knowledge of open-ocean biogeography, especially in the Atlantic and Pacific oceans. There are fewer collections from the Indian Ocean, and it is not so well known.

Although close correlation might be expected between surface features of the open-ocean and epipelagic biogeography, it seems less likely that the distribution of deeper-living mesopelagic animals would be closely correlated with near-surface oceanographic features. Numerous studies have demonstrated, however, that faunal breaks between regions often correlate with major physical oceanographic phenomena. These frequently have near-surface manifestations, such as at the edge of the Gulf Stream and at the boundary between the Subarctic and North Atlantic Temperate regions (Backus et al., 1977). On the other hand, boundaries between the subdivisions of the regions (faunal provinces) correspond to less prominent physical oceanographic features, frequently with little or no surface manifestation (Backus et al., 1977).

Drawing on many studies, I have compiled a map (Figure 25) showing the major open-ocean mesopelagic regions following the terminology and Atlantic boundaries of Backus et al. (1977). Boundaries for the Indian Ocean were modified from Gibbs and Hurwitz (1967), Nafpaktitis (1978), Nafpaktitis and Nafpaktitis (1969), Rochford (1966a), Sverdrup, Johnson, and Fleming (1942), and Wyrtki (1971). Those for the Pacific follow Brinton (1962), McGowan (1971, 1976), Parin (1961), Parin et al. (1973), and Wisner (1976). Boundaries for the Southern Ocean regions follow Backus (pers. comm., 1979) and McGinnis (1974, 1982) with modifications from Wyrtki (1971).

The mesopelagic southern temperate regions were examined in detail. The existence of a South Atlantic Temperate Region is rather poorly documented, and a possible South Indian Temperate is even more poorly documented. Parin et al. (1974) recognized the subtropical affinities of some species in the South Atlantic Temperate Region and included them in what was called the Peripheral Central or Subtropical pattern. There is, however, considerable confusion, as Krefft (1976) and Gibbs and McKinney (1988) pointed out, because some species in the Subantarctic Water Mass are confined to its northernmost edges, i.e., the southern part of the Subtropical Convergence (STC), whereas other species occur in the STC and extend to the north and south of it, and still other species have their southern limit in the STC but are primarily found to the north in subtropical waters. Krefft (1976) discussed those species mentioned by Parin et al. (1974) and gave examples of several other species as better fitting a “Convergence Pattern” (Krefft, 1976, fig. 3). This “Convergence Fauna” had first been recognized by Gibbs (1968) as a distinct zoogeographic region. It is approximately equivalent to what is herein recognized as the South Atlantic Temperate Region (Figure 25), and what McGinnis (1977, 1982) recognized as the Subtropical Convergence. Hulley (1981), however, considered the Atlantic South Temperate pattern to be broader in scope, consisting of a Convergence Subpattern and a Subantarctic Subpattern. Gibbs and McKinney (1988) considered that any species that mainly occurred between 35°S–45°S to have convergence distributions even if specimens also had been captured to the north or south of those limits.

FIGURE 25.—Mesopelagic zoogeographic regions (see text for explanation).

Boundaries for the South Atlantic and South Indian Temperate regions were set following the suggestions of Richard Backus (pers. comm., 1979). The boundary between the Temperate and South Subtropical regions follows the 13°C isothern at 200 m (Backus et al., 1977). This is close to, but not exactly the same as, the northern edge of the Subtropical Convergence as delimited by McGinnis (1974, 1982) based on salinities of 34.6–34.8 per mil at 200 m. It also corresponds reasonably well with the Subantarctic Convergence of Ivanov and Neiman (1965) based on dynamical considerations. The southern edge of the STC forms the boundary between the South Temperate regions and the Subantarctic Region. Thus, in the Atlantic and Indian oceans, the entire Subtropical Convergence and adjacent waters to the north are included in the South Temperate regions. In the Pacific, the edges of mesopelagic fish distribution do not seem to correspond closely to the southern edge of the STC of McGinnis (1974, 1982). Consequently, the boundaries for the South Pacific Temperate Region are taken from the “South Pacific Transition Faunal Province core” of McGowan (1976:426). His provinces are based on the presence of faunal assemblages, and the core is where 100% of the assemblage occurs.

The discussion of the species distributions and their relationships to recognized mesopelagic zoogeographic regions will start with the North Atlantic. In order to deal with the geographic aspects in an orderly fashion, the discussions will proceed through the South Atlantic and South Indian oceans, including subantarctic affinities, then the remainder of the Indian Ocean, and, finally, the Pacific from south to north.

In the Atlantic, where the mesopelagic zoogeography is best known, my findings generally agree with those of Nafpaktitis et al. (1977) and Backus et al. (1977). The species of Nannobrachium with the most restricted distribution is N. isaacsi (Figure 16), characterized by Nafpaktitis et al. (1977) and Backus et al. (1977) as a tropical species. Nannobrachium isaacsi is widespread in the eastern tropical Atlantic and less common in the central tropical Atlantic. Certainly, the Mauritanian Upwelling Region is a center of abundance, but whether it truly occurs in two disjunct regions in the eastern Atlantic is not clear from the distribution shown by Nafpaktitis et al. (1977, fig. 138) nor from the samples available to me. Such an apparent distribution may result from uneven sampling efforts.

Of the three remaining species of Nannobrachium widely distributed in the Atlantic (N. atrum, N. lineatum, and N. cuprarium), only N. cuprarium (Figure 16) is unequivocally a bipolar subtropical species largely confined to the central gyres. In the North Atlantic, Hulley and Krefft (1985) found N. cuprarium to be the only myctophid characteristic of the South Sargasso Sea Province, part of the North Atlantic Subtropical. In the South Atlantic, because of its abundance in the central part of the South Atlantic Central Gyre, Hulley (1981:195) termed it a “gyral-eye” species.

Both N. lineatum and N. atrum have broader distributions that extend into the Indian and Pacific oceans, although as discussed under the species accounts, it is likely that the Indo-Pacific specimens of N. lineatum belong to more than one species, perhaps all different from the Atlantic form. Nafpaktitis et al. (1977) characterized N. lineatum in the Atlantic as not fitting any distribution pattern particularly well; however, in the Walther Herwig collections, N. lineatum (Figure 16) is most abundant in the Tropical Region and less abundant in the North Atlantic Subtropical (Hulley, 1981; and pers. comm., 1980), suggesting that it is primarily a tropical species. It seems to be virtually absent from the South Atlantic Subtropical, where the Walter Herwig took large numbers of the closely related N. cuprarium. Small numbers of both species were taken together by the Walter Herwig in the eastern North Atlantic Subtropical Region.

The distribution of N. atrum (Figure 5) in the Atlantic was characterized by Nafpaktitis et al. (1977:206) as “bipolar questionably subtropical” or as “bipolar temperate–semisubtropical.” The uncertainty is due to a lack of specimens from some parts of the subtropics (including the southern Sargasso Sea) and an abundance in the temperate northeastern Atlantic. In the South Atlantic, McGinnis (1974, 1982, as L. niger-ater complex) found the southern limit of its distribution to coincide with the Subtropical Convergence. Both this study (Figure 5) and the Walther Herwig material (Hulley, 1981, and pers. comm., 1980) confirm that N. atrum is bipolar in distribution in subtropical and temperate waters and is not found in the tropics except as waifs. Thus, its range in the North Atlantic, as well as its presence in both the South Atlantic Subtropical and less well known South Atlantic Temperate regions, suggests a bipolar temperate–semisubtropical distribution.

The Subtropical Convergence also coincides with the southernmost limit for the Atlantic distribution of N. wisneri, an example of a South temperate–semisubtropical species (Figure 19). Nannobrachium wisneri is one of two Southern Hemisphere circumglobal (or nearly circumglobal) species. It shows a tendency to extend northward in the eastern Atlantic as does N. achirus, the second circumglobal species, undoubtedly because of the cold, northward-flowing Benguela Current (Hulley, 1981; and pers. comm., 1980). In the South Subtropical regions, N. wisneri occurs only in the southern parts, hence the designation “semisubtropical.” In his investigations, Hulley (1986b:243) basically agreed with the distribution but characterized the pattern of N. wisneri (his Lampanyctus sp. B) as temperate, specifically, an example of a South Temperate Convergence Subpattern. As McGinnis (1982:69, Lampanyctus sp. A) noted, the southern limits of the distribution of N. wisneri tend to correspond to the northern limits of N. achirus.

Nannobrachium achirus is a subantarctic species whose distribution (Figure 19) lies largely between the Subtropical Convergence in the north and the Antarctic Polar Front to the south (McGinnis, 1974, 1982). (The Antarctic Polar Front is the Antarctic Convergence of Deacon (1937) and MacKintosh (1946), based on salinity and temperature gradients, and of Ivanov and Neiman (1965), based on dynamical considerations.) The few specimens from north of the Subtropical Convergence in the southwestern Atlantic and southeastern Pacific were probably carried northward by the Falkland Current (Krefft, 1976:445) and by the Peru Current (McGinnis, 1982:44), respectively. McGinnis (1982) points out, however, that of the 10 species of myctophids whose distribution he designated Pattern III (from the Subtropical Convergence on the north to the Antarctic Polar Front on the south, i.e., a subantarctic distribution) only N. achirus regularly extends south of the Antarctic Polar Front. Hulley (1981:184) also noted this, characterizing N. achirus as having a broadly antarctic distribution based on Walther Herwig material but then suggested that its “spawning area indicates a subantarctic pattern.” Subsequently, Hulley (1986b: 242) characterized the distribution as Widespread Temperate, with a South Temperate Subantarctic Subpattern.

Both samples of N. achirus available from the South Indian Ocean (Figure 19) were captured near the south edge of the Subtropical Convergence as delimited by McGinnis (1974, 1982). His one South Indian Ocean sample (McGinnis, 1982, fig. 31) also was taken in the STC. This is consistent with the characterization of N. achirus as a subantarctic species.

As in the Atlantic, in the Indian Ocean, N. wisneri occurs north of the Subtropical Convergence and, therefore, north of most of the collections of N. achirus (Figure 19). The few collections available were consistent with a temperate-semisubtropical distribution for this species. Because both this species and N. achirus occur to the east and west of the South Indian Ocean, both are presumed to have an unbroken circumglobal distribution; however, N. wisneri may be rare or absent in the region south of Australia and between Australia and New Zealand. A number of collections were available from those regions that contained specimens of either N. achirus (Figure 19) or N. atrum (Figure 5) but not of N. wisneri.

Nannobrachium atrum is common and widespread in the Subtropical and Temperate regions of the Indian Ocean, as it is in the Atlantic. This agrees with Nafpaktitis and Nafpaktitis (1969) but not with Kotthaus (1972b), who reported N. atrum from near the equator and at about 4°S. Of the material examined, the southernmost record was near the southern edge of the Subtropical Convergence, consistent with a temperate-semisubtropical species.

The three remaining Indian Ocean species are tropical or subtropical in their distribution. Nannobrachium indicum, the only species of Nannobrachium endemic to the Indian Ocean, is restricted to the Indian Tropical Region (Figure 5). The southern boundary of the Indian Tropical Region (Figure 25) is north of the Equatorial Frontal Water, which Rochford (1966a:6) delimited on the basis of salinity and oxygen differences. He located this Frontal water at about 9°S, “just south of the northern boundary of the south Equatorial current.” This is about at the boundary of the Indian Equatorial and Central Water Masses (Sverdrup et al., 1942). It is probably a significant Zoogeographie boundary. Not only does the boundary correlate with the break in distribution patterns for N. indicum and N. atrum, but it also has been shown by Gibbs and Hurwitz (1967) to correspond to a boundary between two morphologically distinct species of Chauliodus in the western Indian Ocean. Nafpaktitis and Nafpaktitis (1969) found that a number of other species of myctophids were found either to the north or to the south of approximately 10°S in the western Indian Ocean, and Nafpaktitis (1978) found the same for a number of species of Diaphus.

The four samples of N. lineatum from the Indian Ocean are consistent with the distribution pattern for this species in the Atlantic: more abundant in the Tropical Region, with sparse numbers in the South Indian Subtropical Region (Figure 16). The tendency to extend toward the south along the east coast of Africa is probably due to the southward-flowing Agulhas Current. According to Rochford (1966b), Banda Intermediate water of lower salinity moves toward the west at depths of 900–1100 m from about 10°S-15°S toward Madagascar. In addition, Rochford (1964) found evidence that high salinity water masses from the Gulf of Aden and from the Persian Gulf move toward the south along the East African coast. Part of this water turns east at the equator and part follows the African coast past Madagascar at intermediate depths varying from 300–700 m, depending on the origins of the water and the salinity maxima. Thus, both of these general water movements could help account for the occurrence of a tropical species to the south along the East African coast.

The few samples of N. nigrum from the Indian Ocean indicate that this species is present only in the extreme northeast portion of the the South Indian Subtropical. Given its wide occurrence in the tropical Pacific and the various East Indian seas and with more extensive collecting, N. nigrum may be expected to tum up in the extreme eastern portion of the Indian Tropical as well.

Over the past few years, Pacific zoogeography has been studied in greater detail, although that detail is still not equal to that of the Atlantic, and there has been no attempt to divide Zoogeographic regions into provinces as Backus et al. (1977) have done for the Atlantic. In this regard, McGowan (1986:195) compared the characteristics of the three major pelagic faunal regions of the North Pacific (Subarctic, Central, and Eastern Tropical Pacific) and found no compelling evidence for sub- units, such as provinces, although he did discuss the presence of “several cyclonic sub-systems” within the Subarctic system; however, because they contain no endemics or unique species assemblages, he considered them to be “too ‘unpredictable’ to have served as habitats or centers for diversi fication.” In the Pacific, McGowan (1974, 1976) and Reid et al. (1978) recognized five major faunal assemblages (Central, Transition, Equatorial, Eastern Tropical Pacific, and Subpolar—i.e., Subarctic and Subantarctic) and their core regions (where 100% of the faunal group species are found). All the faunal regions correspond to water masses and provide a useful framework to compare distribution patterns. The species of Nannobrachium can contribute to our understanding of Pacific zoogeography because there are many Pacific species, most of which are endemic.

The southernmost species, N. achirus (Figure 19), is clearly in the Subantarctic Region, although as discussed earlier, it also is known from south of the Antarctic Polar Front (McGinnis, 1982). In the southeastern Pacific, N. achirus is found only in the southern part of the Subantarctic Region, although McGinnis records specimens from as far north as 33°S. This is the region where the West Wind Drift squeezes through the Drake Passage. The Subantarctic Region is broad here, extending north along the west coast of South America until it blends in with the Peruvian Upwelling Region of the Peru-Chile Current (Figure 25).

The distribution of N. wisneri (Figure 19) is in, and to the north of, the South Pacific Temperate Region, so it is clearly a temperate-semisubtropical species. Many specimens occurred south of the Subtropical Convergence as delimited by McGinnis (1974, 1982), but their distribution corresponds almost precisely with the core of the Southern Transition Faunal Province of McGowan (1976, fig. 1). The distribution of N. wisneri also agrees with that of the “Convergence Fauna” (Gibbs, 1968:3) in the Pacific. Thus, although there is strong evidence for a recognizable Temperate Region in the South Pacific, its fauna does not seem to follow the same physical parameters as the fauna of the Atlantic and Indian Temperate regions.

In the Pacific, N. atrum (Figure 5) is found only in the southwestern portion, where it is common and appears to have a temperate-semisubtropical distribution. Nannobrachium atrum and N. wisneri are almost mutually exclusive in the South Pacific, in contrast with the South Atlantic where they co-occur widely. They apparently also co-occur in the Indian Ocean. In the South Pacific, the boundary between the two species appears to be around 170°W, with only one collection of N. wisneri to the west and one collection of N. atrum to the east of 170°W.

Nannobrachium idostigma is found throughout the Eastern Tropical Pacific Region and in the northern part of the Peruvian Upwelling Region (Figure 10). For this reason, it is perhaps best described as an Eastern Tropical Pacific species having affinities to the Peruvian Upwelling Region. Its restricted eastem Pacific distribution resembles that of N. isaacsi in the Atlantic. Beklemishev (1973), Parin and Bekker (1981), and Bekker (1983) considered that both this species and N. ritteri, which is also eastern Pacific but further north off the west coast of North America, display what they termed a “far-neritic” or “extended neritic” pattern. (See the discussion under the species account for N. ritteri for greater details.)

None of the species of Nannobrachium has a distribution limited to the South Pacific Subtropical Region. Nannobrachium nigrum (Figure 5), however, has a broad-ranging distribution that encompasses much of both the North and South Pacific Subtropical regions and the intervening Tropical Region. Nannobrachium nigrum is absent from the Eastern Tropical Pacific Region but appears to be very widespread and common throughout the seas of the western Pacific, extending into the eastern Indian Ocean.

The only other species of Nannobrachium that has a comparably wide distribution in the Pacific is N. lineatum (Figure 16). Specimens of various forms of this species were taken infrequently from widely distant localities in the Pacific Tropical and the North and South Pacific Subtropical regions, consistent with the pattern in the Atlantic and Indian oceans. One locality immediately south of the Eastern Tropical Pacific Region suggests that N. lineatum may ultimately be found in that region as well.

Nannobrachium gibbsi is widespread in the southern half of the Tropical and northern half of the South Pacific Subtropical regions (Figure 5), suggesting a south tropical-semisubtropical distribution. A few specimens taken in the extreme eastern part of the South Pacific Temperate Region near the subtropical-temperate border may represent waifs.

Nannobrachium crypticum is a tropical species largely confined to the Pacific Tropical Region (Figure 19). The few records from immediately south of the tropical-subtropical border probably represent imprecision in the location of that border or perhaps the boundary fluctuates or is not sharp.

Two species are largely restricted to the North Pacific Subtropical Region, N. bristori (Figure 10) and N. hawaiiensis (Figure 19), although both are commonly found in the southern part of the California Current, an area of mixing along the west coast of North America. Both species also have been taken beyond the borders of the Subtropical Region in adjacent regions, but these sporadic records can be considered waifs, and both species are designated as having North Pacific Subtropical distributions. The small number of locality records for N. bristori in the western Pacific is probably a function of the fewer samples available from that region, as well as the relative rarity of this species in collections; however, it also may be due to differences between eastern gyre and western gyre faunas in the North Pacific Subtropical Region (Sverdrup et al, 1942; Barnett, 1975, 1983, 1984).

All three remaining species of Nannobrachium in the North Pacific belong to the Regale group (Figure 10). Nannobrachium regale is broadly distributed across the North Pacific in all parts of the North Pacific Temperate and Subarctic regions. According to Fedorov (pers. comm., 1979) the breeding range for N. regale in the western Pacific corresponds almost exactly to the Subarctic Region; however, there also is a region to the south where expatriates can be found that corresponds closely to the North Pacific Temperate Region.

Nannobrachium ritteri appears to be a species of the North Pacific Temperate Region, but it is restricted to the eastern part, especially the California Current system along the west coast of North America. It is absent from the Subarctic Region and extends west from the U.S. coastline to about 45°N, 155°W (Wisner, 1976). The locality record at about 45°N, 165°W represents a range extension based on a single large specimen that probably was a waif.

The extremely limited distribution pattern of N. fernae appears to be real and not the result of sampling effort. Nannobrachium fernae is restricted to the east-central portion of the North Pacific Temperate Region, which corresponds almost precisely with the core region of the “North Transition Faunal Province” (McGowan, 1976:426). Although several invertebrates show a similar distribution (Brinton, 1962; McGowan, 1971), N. fernae appears to be the only fish found so far that shows such a distribution.

McGowan (1971:17) discussed the “Transition Faunal Province” in detail, giving numerous examples of North Pacific Temperate (= Transition Zone fauna) species from the zooplankton. He also pointed out the possibility of a wind driven westward countercurrent with a transport as large as 4–6 × 10⁵ cubic meters per second at about 38°N based on data from Dodimead et al. (1963) and Fofonoff (1960) to account for the maintenance of planktonic organisms in a region generally shown on a broad scale as having only eastward-flowing surface currents (Sverdrup et al., 1942; Fleming, 1955).

When the distribution patterns for all species within each species group are compared, it is clear that there is remarkably little overlap between species, especially within the Nigrum (Figure 5) and Achirus (Figure 19) species groups. The only major exceptions are within the Regale group (Figure 10, N. ritteri) and the Cuprarium group (Figure 16, N. lineatum). Furthermore, there is little overlap when the species-group distributions as a whole are compared. Again, this is especially clear in comparing the distribution patterns of the Nigrum group as a whole with that of the Achirus group, although it also holds in large part when they are compared with the distribution of the Regale group.

It is shown that the species of Nannobrachium have discrete and distinctive distribution patterns that, for the most part, correlate with physical features of the open ocean. Furthermore, their distribution patterns correspond to and elucidate various Zoogeographic regions that have been previously recognized on the basis of the distribution patterns of other organisms.

Summary and Conclusions

In the lanternfish fish family Myctophidae, the genus Lampanyctus (sensu lato) is one of the most speciose. Within that genus, those species with reduced pectoral fins have long been taxonomically confusing. More than 9000 specimens were studied worldwide in an attempt to resolve the taxonomic problems. The short-pectoral-finned group was found to contain 17 species that could be divided into five species groups based on shared and unique characters.

As herein recognized, the genus Nannobrachium includes those species in the tribe Lampanyctini with the following combination of characters: no pectoral fins or short fins with a narrow base; a vertically elongate squarish otolith with smooth margins; reduced musculature resulting in a soft, flaccid body; a “pinched” body profile with concave dorsal and ventral profiles behind the head; and swimbladder atrophied in adults.

Within the genus Nannobrachium, the Nigrum species group contains four species, including the type-species for the genus, Nannobrachium nigrum Günther, 1887. The other three species in the Nigrum group are N. atrum (Taning, 1928) (long confused with N. nigrum) and two new species, N. gibbsi and N. indicum. All species in the Nigrum group share the unique character of very thin and flexible rays in extremely short pectoral fins in the adult, usually reaching less than one-half the distance to the pelvic-fin insertion.

The species of the Nigrum group are widely distributed. Nannobrachium atrum is the most widespread, being found in the North and South Atlantic, South Indian, and western part of the South Pacific oceans. Nannobrachium nigrum is found in the tropical Pacific, excluding the Eastern Tropical Pacific Region, through the East Indian archipelago as far west as the extreme eastern tropical Indian Ocean. Nannobrachium gibbsi is found in the tropical and subtropical South Pacific to slightly north of the equator. Nannobrachium indicum is the only species of Nannobrachium endemic to the Indian Ocean, where it is restricted to the tropics.

All species of the Regale group have well-developed (for Nannobrachium) pectoral fins that reach to, or nearly to, the pelvic-fin insertion and have the VLO photophore low on the side of the body. Of the five species in the group, only one, N. bristori, is a new species. The entire group is restricted to the Pacific Ocean and, except for N. idostigma (Parr, 1931), which is restricted to the Eastern Tropical Pacific and Peruvian Upwelling regions, all species are found only in the North Pacific. Nannobrachium regale Gilbert, 1891, is found across the entire North Pacific, primarily in the Subarctic Region. Nannobrachium bristori also is found across the North Pacific, but it also occurs to the south, in the subtropics. The two remaining species have restricted distributions: Nannobrachium ritteri (Gilbert, 1915) is found in the eastern Pacific throughout the eastern portions of the North Pacific Temperate Region and in the California Current, whereas Nannobrachium fernae (Wisner, 1971) (with the most restricted distribution of all species of Nannobrachium) is found in the eastern portion of the main part of the North Pacific Temperate Region.

Both species of the Cuprarium group share the unique character of pigmentation on the posterior portions of the supracaudal and infracaudal luminous glands. The smaller species, N. cuprarium (Tåning, 1928), is restricted to the subtropical regions of the North and South Atlantic oceans. The larger species, N. lineatum (Tåning, 1928), is the largest species of Nannobrachium, reaching a size, in the Atlantic, well in excess of 200 mm. Although it is widespread throughout the Atlantic, it seems to be especially abundant in the tropics. In the Indian and Pacific oceans, N. lineatum also is widespread but seems to be represented by two or more forms.

The Achirus species group contains five species, of which four are newly described herein; only N. achirus (Andriashev, 1962) had been described previously. All species in this group share an ontogeny resulting in lack of pectoral-fin development. In all species at a particular size, which varies with the species, the pectoral fins slow or stop their growth and eventually become overgrown with skin, so that usually no pectoral fins are visible in the adult. During the slowing of pectoral-fin growth, the rays point downward, become thicker, broad, and bone-like, and eventually fuse to the posterior edge of the scapula. Nannobrachium achirus is the most southerly of the species of Nannobrachium, being found circumglobally in the subantarctic. Nannobrachium wisneri is found to the north and occurs nearly circumglobally in the temperate regions, except in the vicinity of Australia and New Zealand. The remaining three species are found only in the Pacific. Nannobrachium phyllisae is restricted to the Peruvian Upwelling Region along the west coast of South America. Nannobrachium hawaiiensis is found across the North Pacific Subtropical Region and always has the most extreme loss of pectoral fins, perhaps occurring at or near the time of postlarval transformation. The remaining species, N. crypticum, also is found across the Pacific but is restricted to the Equatorial Region. The latter has the greatest retention of its pectoral fins, with the presence of some exterior vestige in the largest specimens available.

The Isaacsi species group is represented by a single species, N. isaacsi (Wisner, 1974). It is characterized by the position of the VO₂ photophore, above and slightly before the VO₁, which is unique for Nannobrachium. Nannobrachium isaacsi is restricted to the eastern tropical Atlantic Ocean and is especially common in the Mauritanian Upwelling Region.

In general, the distribution patterns of the species of Nannobrachium are distinctive and correspond to previously recognized Zoogeographic regions, having boundaries that correlate with oceanographic features. In addition, the distribution patterns for the species and species groups of Nannobrachium show remarkably little overlap in distributions.

Appendix Tables

TABLE A1.—Nigrum group, N. crypticum and N. bristori; modal characters with extremes in parentheses.

TABLE A2.—AO photophores, all species of Nannobrachium.

TABLE A3.—Gill rakers, all species of Nannobrachium.

TABLE A4.—Tooth patches, lower limb of second gill arch, all species of Nannobrachium.

TABLE A5.—Fin rays, all species of Nannobrachium.

TABLE A6.—Luminous caudal gland scales, all species of Nannobrachium.

TABLE A7.—Lateral line organs, all species of Nannobrachium.

TABLE A8.—Vertebrae, all species of Nannobrachium.

TABLE A9.—Regale group: Modal characters with extremes in parentheses.

TABLE A10.—Cuprarium group and N. isaacsi: Modal characters with extremes in parentheses.

TABLE A11.—Achirus group: Modal characters with extremes in parentheses.

Appendix Tables 12 to 14: Explanation

The following tables will help to identify specimens through the use of a series of measurements to distinguish between pairs of species. The pairs of species are primarily those within a species group, but they also may include selected pairs of species from different species groups when the species are likely to co-occur and are morphologically similar. To use a table effectively it is necessary to have some idea of the identification of the specimen at hand, usually by having identified it to one of two possibilities through use of a key. Turning to the table for that species group, the intersection of the column and row with the two species names will give 4 or 5 quotients (Q) for which 8 or 10 measurements are needed. Once the measurements have been obtained and the necessary division operation done to produce the quotients, these must be multiplied by the proper function (F) following each quotient. These S values (either positive or negative values) are then added arithmetically and the final value compared with the Discriminant Value (D.V.) given at the bottom of the box. An obtained value will be larger than the D.V. for one species and smaller than the D.V. for the other species in almost all cases. A few specimens, probably only 1 or 2% (certainly less than 5% of the total number measured), for pairs of species that are morphologically the most similar, have been found to give an obtained value on the “wrong” side of the D.V. Thus, this technique is not infallible, but it is merely another aid to the identification of these morphologically similar species. The abbreviations for the measurements are as follows.

AFB | Anal-fin base length
CPD | Caudal peduncle depth
CPL | Caudal peduncle length
DFB | Dorsal-fin base length
ED | Eye diameter
HD | Head depth
HL | Head length
IGEL | Infracaudal gland, extreme length
IGS | Infracaudal gland, solid length
PADL | Post adipose length
PANL | Preanal length
PDD | Predorsal depth
PDL | Predorsal length
PAL | Pelvic to anal length
SGEL | Supracaudal gland, extreme length
SGS | Supracaudal gland, solid length
SL | Standard length
SOL | Snout to orbit length
UJL | Upper-jaw length

TABLE A12.—Discrimination values for distinguishing between pairs of species in the the Nigrum group, N. crypticum, and N. bristori using mensuristics.

TABLE A13.—Discrimination values for distinguishing between pairs of species in the Regale group using mensuristics.

TABLE A14.—Discrimination values for distinguishing between pairs of species in the Achirus group using mensuristics.

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1953.   Checklist of Philippine Fishes. U.S. Fish and Wildlife Service, Research Report, 20:1–977.

Huang, Z., and J. Yang

1983.   [The Deep-Sea Fishes from the Adjacent Waters of Dongsha Islands in the South China Sea.] In J. Yang and Z. Huang, editors, Contributions on Marine Biological Research of the South China Sea, pages 234–255. Beijing: Ocean Publishing. [In Chinese, with English abstract]. [Not seen; fide J. Paxton.]

Hubbs, C.L., and K.M. Lagler

1958.   Fishes of the Great Lakes Region. Bulletin of the Cranbrook Institute of Science, 26:i–xii, 1–135.

Hubbs, C.L., and R.L. Wisner

1964.   Parvilux, a New Genus of Myctophid Fishes from the Northeastern Pacific, with Two New Species. Zoologische Mededelingen, Uitgegeven Door Het Rijksmuseum van Natuurlijke Historie te Lieden, 39:445–563.

Hulley, P.A.

1972.   A Report on the Mesopelagic Fishes Collected during the Deep-Sea Cruises of R.S. Africana II, 1961–1966. Annals of the South African Museum, 60(6):197–236.

1981.   Results of the Research Cruises of FRV “Walther Herwig” to South America, LVII: Family Myctophidae (Osteichthys. Myctophiformes). Archives Fischerei Wissenschaft, 31(1):1–300.

1984a. The South African Museum's Meiring Naude Cruises, Part 14: Family Myctophidae (Osteichthyes, Myctophiformes). Annals of the South African Museum, 93(2):53–96.

1984b. Myctophidae. In P.J.P. Whitehead, M.-L. Bauchot, J.-C. Hureau, J. Nielsen, and E. Tortonese, editors. Fishes of the Northeastern Atlantic and the Mediterranean, 1:429–483. Paris: UNESCO.

1986a. A Taxonomic Review of the Lanternfish Genus Triphoturus Fraser-Brunner, 1949 (Myctophidae, Osteichthyes). Annals of the South African Museum, 97(4):71–95.

1986b. Lanternfishes of the Southern Benguela Region, Part I: Faunal Complexity and Distribution. Annals of the South African Museum, 97(7):227–249.

1986c. Family No. 86: Myctophidae. In M.M. Smith and P.C. Heemstra, editors, Smith's Sea Fishes, pages 282–321. Johannesburg, South Africa: Macmillan.

1989.   Lanternfishes (Osteichthys, Myctophidae) from the Region of the Saint Paul and Amsterdam Islands (Southern Indian Ocean). Bulletin du Muséum d'Histoire Naturelle de Marsaille, 49:49–58.

1990.   Family Myctophidae, Lanternfishes. In O. Gon and P.C. Heemstra, editors, Fishes of the Southern Ocean, pages 146–178. Grahamstown: Smith Institute of Ichthyology.

1995.   Lanternfishes. In J.R. Paxton and W.N. Eschmeyer, editors, Encyclopedia of Fishes, pages 127–128. San Diego: Academic Press.

Hulley, P.A., and G. Krefft

1985.   A Zoogeographic Analysis of the Fishes of the Family Myctophidae (Osteichthys, Myctophiformes) from the 1979–Sargasso Sea Expedition of R.V. Anton Dorhn. Annals of the South African Museum, 96(2):19–53.

Ivanov, Yu.A., and V.G. Neiman

1965.   [Frontal Zones of the Southern Ocean.] In The Antarctic, pages 157–174. Moscow: The Academy of Sciences of the USSR, Soviet Committee on Antarctic Research. [Translated from Russian by the Indian National Scientific Documentation Centre, Delhi, India, 1971, 269 pages. Available from U.S. Department of Commerce, National Technical Information Service, Springfield, Virginia 22151.]

Jordan, D.S., and B.W. Evermann

1896a. A Checklist of the Fishes and Fish-like Vertebrates of North and Middle America. U.S. Commission of Fish and Fisheries, Report, 21(5):209–584.

1896b. The Fishes of North and Middle America: A Descriptive Catalogue of the Species of Fish-like Vertebrates Found In the Waters of North America, North of the Isthmus of Panama. Bulletin of the U.S. National Museum, 47(1):1–685.

Jordan, D.S., B.W. Evermann, and H.W. Clark

1930.   Checklist of the Fishes and Fish-like Vertebrates of North and Middle America North of the Northern Boundary of Venezuela and Columbia. In Report of the U.S. Commissioner of Fisheries for the Fiscal Year 1928, 670 pages. [Reprint 1955. Washington, D.C.]

Kailola, P.J.

1987.   The Fishes of Papua New Guinea: A Revised and Annotated Checklist, 1: Myxinidae to Synbranchidae. Papua New Guinea Department of Fisheries and Marine Research, Research Bulletin, 41:1–194.

Karnella, C.

1987.   Family Myctophidae, Lanternfishes. In R.H. Gibbs, Jr., and W.H. Kruger, editors, Biology of Midwater Fishes of the Bermuda Ocean Acre. Smithsonian Contributions to Zoology, 452:51–168.

King, J.E., and R.T.B. Iversen

1962.   Midwater Trawling for Forage Organisms in the Central Pacific 1951–1956. U.S. Fish and Wildlife Service, Fishery Bulletin, 62:271–321.

Kinzer, J., and K. Schulz

1985.   Vertical Distribution and Feeding Patterns of Midwater Fish in the Central Equatorial Atlantic, I: Myctophidae. Marine Biology, 85:313–322.

Kotthaus, A.

1972a. Die meso-und bathypelagischen Fische der “Meteor”—Rossbreiten-Expedition 1970 (2. and 3. Fahrtabschnitt). “Meteor” Forschung-Ergebnisse, series D, 11:1–28. [In German; English abstract.]

1972b. Fische des Indischen Ozeans, A: Systematischer Teil IX: Iniomi (Nachtrag: Fam. Myctophidae). “Meteor” Forschung-Ergebnisse, series D, 12:12–35. [In German, with English abstract.]

Krefft, G.

1974.   Investigations on Midwater Fish in the Atlantic Ocean. Berichte der Deutschen Wissenschaftlichen Kommission für Meeresforschung, 23(3):226–254.

1976.   Distribution Patterns of Oceanic Fishes in the Atlantic Ocean; Selected Problems. Revue des Travaux de l'Institute des Peches Maritimes, 40(3–4):439–460.

Krefft, G., and V.E. Bekker

1973.   Myctophidae. In J.C. Hureau and Th. Monod, editors, Checklist of the Fishes of the North-Eastern Atlantic and of the Mediterranean (CLOFNAM), part 1, pages 171–198. Paris: UNESCO.

Kulikova, E.G.

1960.   [Lampanyctus (Genus Lampanyctus) of the Far Eastern Seas and the Northwestern Pacific.] Transactions of the Institute of Oceanology, Academy of Sciences of the USSR, 31:166–204. [Original in Russian; Translation No. 44, pages 1–43. National Marine Fisheries Service Ichthyological Laboratory, Museum of Natural History, Washington, D.C.]

Lancraft, T.M., and B.H. Robison

1979.   Evidence of Postcapture Ingestion by Midwater Fishes in Trawl Nets. Fishery Bulletin, 77(3):713–715.

Lavenberg, R.J., and J.E. Fitch

1966.   Annotated List of Fishes Collected by Midwater Trawl in the Gulf of California, March–April 1964. California Fish and Game, 52(2):92–110.

Leviton, A.E., R.H. Gibbs, Jr., E. Heal, and C.E. Dawson

1985.   Standards in Herpetology and Ichthyology, Part 1: Standard Symbolic Codes for Institutional Resource Collections in Herpetology and Ichthyology. Copeia, 1985(3):802–832.

Loeb, V.J.

1979a. Larval Fishes in the Zooplankton Community of the North Pacific Central Gyre. Marine Biology, 53:173–191.

1979b. Vertical Distribution and Development of Larval Fishes in the North Pacific Central Gyre during Summer. Fishery Bulletin, 77(4):777–793.

1980.   Patterns of Spatial and Species Abundance Within the Larval Fish Assemblage of the North Pacific Central Gyre during Late Summer. Marine Biology, 60:189–200.

1986.   Importance of Vertical Distribution Studies in Biogeographic Understanding: Eastern Tropical Pacific vs. North Pacific Central Gyre Ichthyoplankton Assemblages. In A.C. Pierrot-Bults, S. van der Spoel, B.J. Zahuranec, and R.K. Johnson, editors, Pelagic Biogeography, pages 177–181. Paris: UNESCO Technical Papers in Marine Science, number 49.

MacKintosh, N.A.

1946.   The Antarctic Convergence and the Distribution of Surface Temperatures in Antarctic Waters. Discovery Reports, 23:177–212.

Makushok, V.M.

1970.   [Data on Fishes Collected during the 39th Voyage of the R/V Vityaz in the Kurile-Kamchatka Trench Area during the Summer of 1966.] In V.G. Bogdanov, editor, Proceedings of the Institute of Oceanology, Academy of Sciences, USSR, 86:541–564. [Translation No. 1, 71-50130. Available from U.S. Department of Commerce, National Technical Information Service, Springfield, Virginia 22151.]

Matarese, A.C., A.W. Kendall, Jr., D.M. Blood, and B.M. Vintner

1989.   Laboratory Guide to Early Life History Stages of Northeast Pacific Fishes. NOAA Technical Report, NMFS, 80:1–652. [Not seen; fide H.G. Moser.]

McGinnis, R.F.

1974.   Counterclockwise Circulation in the Pacific Subantarctic Sector of the Southern Ocean. Science, 186:736–738.

1982.   Biogeography of Lanternfishes (Myctphidae) South of 30°S. In D.L. Pawson, editor, Biology of the Antarctic Seas XII. Antarctic Research Series, 35:1–110. Washington, DC.: American Geophysical Union.

McGowan, J.A.

1971.   Oceanic Biogeography of the Pacific. In B.M. Funnell and W.R. Riedel, editors, The Micropaleontology of Oceans, pages 3–74. Cambridge, U.K.: Cambridge University Press.

1974.   The Nature of Oceanic Ecosystems. In C.B. Miller, editor, The Biology of the Oceanic Pacific, pages 9–28. Corvallis, Oregon: Oregon State University Press.

1976.   What Regulates Pelagic Community Structure in the Pacific? In N.R. Andersen, B.J. Zahuranec, editors, Oceanic Sound Scattering Prediction, Marine Science Series, 5:423–443. New York: Plenum.

1986.   The Biogeography of Pelagic Ecosystems. In A.C. Pierrot-Bults, S. van der Spoel, B.J. Zahuranec, and R.K. Johnson, editors, Pelagic Biogeography, pages 191–200. Paris: UNESCO Technical Papers in Marine Science, number 49.

McNulty, J.A., and B.G. Nafpaktitis

1977.   Morphology of the Pineal Complex in Seven Species of Lanternfishes (Pisces: Myctophidae). American Journal of Anatomy, 15(4):509–530.

Merrett, N.R., and H.S.J. Roe

1974.   Pattern and Selectivity in the Feeding of Certain Mesopelagic Fishes. Marine Biology, 28:115–126.

Miller, D.J., and R.N. Lea

1972.   Guide to the Coastal Marine Fishes of California. California Department of Fish and Game, Fish Bulletin, 107: ii + 235 pages.

Moser, H.G., and E.H. Ahlstrom

1974.   Role of Larval Stages in Systematic Investigations of Marine Teleosts: The Myctophidae, a Case Study. Fishery Bulletin, 72(2):391–413.

1996.   Myctophidae: Lanternfishes. In H.G. Moser, editor, The Early Stages of Fishes in the California Current Region, pages 387–475. CalCOFI Atlas 33.

Moser, H.G., E.H. Ahlstrom, and J.R. Paxton

1984.   Myctophidae: Development. In H.G. Moser, editor, Ontogeny and Systematics of Fishes. American Society of Ichthyologists and Herpetologists, Special Publication, 1:218–239.

Moser, H.G., R.L. Charter, P.E. Smith, D.A. Ambrose, S.R. Charter, C.A. Meyer, E.M. Sandknop, and W. Watson

1993.   Distributional Atlas of Fish Larvae and Eggs in the California Current Region: Taxa with 1,000 or More Total Larvae, 1951 Through 1984. CalCOFI Atlas 31, 233 pages.

Moser, H.G., and P.E. Smith

1993.   Larval Fish Assemblages of the California Current Region and Their Horizontal and Vertical Distributions across a Front. Bulletin of Marine Science, 53(2):645–691.

Moser, H.G., P.E. Smith, and L.E. Eber

1987.   Larval Fish Assemblages in the California Current Region, 1954–1960, a Period of Dynamic Environmental Change. California Cooperative Oceanic Fisheries Investigations, 28:97–127. [Not seen; fide H.G. Moser.]

Nafpaktitis, B.G.

1978.   Systematics and Distribution of Lanternfishes of the Genera Lobianchia and Diaphus (Myctophidae) in the Indian Ocean. Science Bulletin, Natural History Museum of Los Angeles County, 30: 4 pages [unnumbered].

1973.   A Review of the Lanternfishes (Family Myctophidae) Described by A. Vedel Tåning. Dana Report, 83:1–46.

Nafpaktitis, B.G., R.H. Backus, J.E. Craddock, R.L. Haedrich, B.H. Robison, and C. Karnella

1977.   Family Myctophidae. In Fishes of the Western North Atlantic, 7: Order Iniomi (Myctophiformes). Sears Foundation for Marine Research, Memoir, 1:13–265.

Nafpaktitis, B.G., and M. Nafpaktitis

1969.   Lanternfishes (Family Myctophidae) Collected during Cruises 3 and 6 of the R/V Anton Bruun in the Indian Ocean. Science Bulletin, Natural History Museum of Los Angeles County, 5:5 pages [unnumbered].

Neighbors, M.A., and B.G. Nafpaktitis

1982.   Lipid Compositions, Water Contents, Swimbladder Morphologies and Buoyancies of Nineteen Species of Midwater Fishes (18 Myctophids and Neoscopelid). Marine Biology, 66:207–215.

Nie, H.H., C.H. Hull, J.G. Jenkins, K. Steinbrenner, and D.H. Bent

1977.   Statistical Package for the Social Sciences. Second edition, 675 pages. New York: McGraw-Hill.

Nielsen, J.G.

1974.   Fish Types in the Zoological Museum of Copenhagen. 115 pages. Copenhagen: Zoological Museum, University of Copenhagen.

Norman, J.R.

1930.   Oceanic Fishes and Flatfishes Collected in 1925–1927 Discovery Report, 2:261–369.

1939.   Fishes; The John Murray Expedition, 1933–34. Scientific Reports, 7(1):1–116.

Novikov, N.P., L.S. Kodolov, and G.M. Gavrilov

1981.   [Preliminary List of Fishes of the Emperor Underwater Ridge.] In Fishes of the Open Ocean, pages 32–35. Moscow: Academy of Sciences of the USSR. [In Russian, with English summary.]

Nybelin, O.

1948.   Fishes Collected by the Skagerak Expedition in the Eastern Atlantic 1946. Goteborgs Kunglige Vetenskaps-och Vitterhets-samhalles Handlingar, (B)5(16):1–95.

Pappenheim, P.

1914.   Die Fische, II: Die Tiefseefische. Deutsche Sudpolar-Expedition, 1901–1903, 15(2): 376 pages. [Not seen; in Krefft and Bekker, 1973.]

Parin, N.V.

1961.   [Distribution of Deep-Sea Fishes in the Upper Bathypelagic Layer of the Subarctic Waters of the North Pacific.] In N.N. Sysoev, editor, Oceanographic Research by the Vityaz in the North Pacific under the I.G.Y. Program. Transactions of the Institute of Oceanology, Academy of Sciences, USSR, 45:262–284. [Translation No. TT 60-50358. Available from U.S. Department of Commerce, National Technical Information Service, Springfield, Virginia 22151.]

1971.   [On Distributional Pattern of Midwater Fishes of the Peru Current Zone.] In L.A. Zenkevitch, editor, Oceanologic Investigations in the Peru Current Area. Transactions of the Institute of Oceanology, Academy of Sciences, USSR, 89:81–95. [In Russian, with English summary.]

1975.   [Change of Pelagic Ichthyocoenoses along the Section at the Equator in the Pacific Ocean between 97° and 155°W.] In M.E. Vinogradov, editor, Ecosystems of the Pelagic Zone of the Pacific Ocean. Transactions of the Institute of Oceanology, Academy of Sciences, USSR, 102:313–334. [In Russian, with English summary.]

1976.   [Comparative Analysis of the Mesopelagic Ichthyocoenoses on Four Polygones in the Western Tropical Pacific.] In N.V. Parin, editor, Biology and Distribution of the Tropical Deep-Sea Fishes. Transactions of the Institute of Oceanology, Academy of Sciences, USSR, 104:195–205. [In Russian, with English summary.]

Parin, N.V., and A.P. Andriashev

1972.   Ichthyological Studies during the 11th Cruise of the Research Vessel Akademik Kurchatov in the South Atlantic. Journal of Ichthyology, 12(5):883–886.

Parin, N.V., A.P. Andriashev, O.D. Borodulina, and V.M. Tchuvasov

1974.   [Midwater Fishes of the Southwestern Atlantic Ocean.] In Z.A. Filatova, editor, Biological Investigations in the Atlantic Section of the Antarctic Ocean. Transactions of the Institute of Oceanology, Academy of Sciences, USSR, 98:76–140. [In Russian, with English summary.]

Parin, N.V., and V.E. Bekker

1981.   [Some Peculiarities of Geographical Distribution of the Pacific Ocean Mesopelagic Fishes (as Exemplified by the Myctophidae).] In Biology of the Pacific Ocean Depths. Proceedings of the XIV Pacific Science Congress (Khabarovsk, August 1979) (Marine Biology), 1:63–71. Vladivostok: Academy of Sciences of the USSR, Far East Science Center. [In Russian, with English summary.]

Parin, N.V., V.E. Bekker, O.D. Borodulina, E.S. Karmouskaya, B.I. Fedoryako, J.N. Shcherbachev, G.N. Pokhilskaya, and V.M. Tchuvasov

1977.   [Midwater Fishes in the Western Tropical Pacific Ocean and the Seas of the Indo-Australian Archipelago.] In N.V. Parin, editor, Deep Sea Biological Investigations in the Western Tropical Pacific. Proceedings of the P. P. Shirshov Institute of Oceanology, Academy of Sciences of the USSR, 107:68–188. [In Russian, with English summary.]

Parin, N.V., V.E. Bekker, O.D. Borodulina, and V.M. Tchuvasov

1973.   [Bathypelagic Fishes of the South-Eastern Pacific Ocean and Adjacent Waters.] In T.S. Rass, editor, Fishes and Squids of the South-Eastern Pacific Ocean. Transactions of the Institute of Oceanology, Academy of Sciences, USSR, 94:71–172. [In Russian, with English summary.]

Parin, N.V., and V.V. Fedorov

1981.   [Comparison of the Midwater Fish Faunas of the Western and Eastern North Pacific.] In Biology of the Pacific Ocean Depths. Proceedings of the XIV Pacific Science Congress (Khabarovsk, August 1979) (Marine Biology), 1:72–78. Vladivostok: Academy of Sciences of the USSR, Far East Science Center. [In Russian, with English summary.]

Parin, N.V., and G.A. Golovan

1976.   [Pelagic Deep-Sea Fishes of the Families Characteristic of the Open Ocean Collected Over the Continental Slope off West Africa.] In N.V. Parin, editor, Biology and Distribution of the Tropical Deep-Sea Fishes. Transactions of the Institute of Oceanology, Academy of Sciences, USSR, 104:250–276. [In Russian, with English summary.]

Parr, A.E.

1928.   Deep-Sea Fishes of the Order Iniomi from the Waters around the Bahama and Bermuda Islands. Bulletin of the Bingham Oceanographic Collection, 3(3):1–193.

1929.   Notes on the Species of Myctophine Fishes Represented by Type Specimens in the United States National Museum. Proceedings of the U.S. National Museum, 76(10):1–47.

1931.   Deep-Sea Fishes off the Western Coast of North and Central America. Bulletin of the Bingham Oceanographic Collection, 2(4):1–53.

Paxton, J.R.

1967a. A Distributional Analysis for the Lanternfishes (Family Myctophidae) of the San Pedro Basin, California. Copeia, 1967(2):422–440.

1967b. Biological Notes on Southern California Lanternfishes (Family Myctophidae). California Fish and Game, 53(3):214–217.

1972.   Osteology and Relationships of the Lanternfishes (Family Myctophidae). Science Bulletin, Natural History Museum of Los Angeles County, 13:1–81.

1979.   Nominal Genera and Species of Lanternfishes (Family Myctophidae). Contributions in Science, Los Angeles County Museum, 316:1–28.

Paxton, J.R., and J.E. Hanley

1989.   Myctophidae. In J.R. Paxton, D.F. Hoese, G.R. Allen, and J.E. Hanley, Zoooligical Catalogue of Australia, 7: Pisces Petromyzontidae to Carangidae, pages 253–270. Canberra: Australian Biological Resources Survey.

Paxton, J.R., J. Lavenberg, and C. Sommer

1995.   [Myctophidae.] In W. Fischer, F. Krupp, W. Schneider, C. Sommer, K.E. Carpenter, and V.H. Niem, editors, Guia FAO para la Identification de Especies para los Fines de la Pesca. Pacifico Centro-Oriental, pages 1315–1321. Rome: FAO. [In Spanish; not seen; fide J. R. Paxton.]

Pearcy, W.G.

1964.   Some Distributional Features of Mesopelagic Fishes off Oregon. Journal of Marine Research, 22(1):83–102.

Pearcy, W.G., E.E. Krygier, R. Mesecar, and F. Ramsey

1977.   Vertical Distribution and Migration of Oceanic Micronekton off Oregon. Deep Sea Research, 24:223–245.

Pearcy, W.G., T. Nemoto, and M. Okiyama

1979.   Mesopelagic Fishes of the Bering Sea and Adjacent Northern North Pacific Ocean. Journal of the Oceanographical Society of Japan, 35(3–4):127–135.

Post, A.

1972.   Ergebnisse der Forschungsreise des FFS WALTHER HERWIG nach Sudamerika, XXIV: Die Chromosomenzahlen einieger atlantischer Myctophidenarten (Osteichthys, Myctophoidei, Myctophidae). Archiv für Fischerei Wissenschaft, 23:89–93.

Quero, J.C.

1969.   List des Poissons Captures au Cours des Peches Pelagiques Profonde de la “Thalasso” dans l'Atlantique Nord-est. Conseil Permenante Internationale Exploration du Mer, circular L, 25:1–5. [Not seen; in Krefft and Bekker, 1973.]

Rao, C.R.

1965.   Linear Statistical Inference and Its Applications. 625 pages. New York: Wiley.

Rass, T.S.

1955.   [Deep Sea Fishes of the Kurile-Kamchatka Trench.] Proceedings of the Institute of Oceanology, Academy of Sciences of the USSR, 12:328–339. [In Russian.]

1968.   [Some Distribution Patterns of Deepwater Fishes.] In Biology of the Pacific Ocean, 7(3):228–246. Moscow: Institute of Oceanology of the Academy of Sciences of the USSR. [In Russian.]

Reid, J.L., E. Brinton, A. Fleminger, E.L. Venrick, and J.A. McGowan

1978.   Ocean Circulation and Marine Life. In H. Charnock, G. Deacon, editors, Advances in Oceanography, pages 65–130. New York: Plenum.

Richardson, S.L., and W.G. Pearcy

1977.   Coastal and Oceanic Fish Larvae in an Area of Upwelling off Yaquina Bay, Oregon. Fishery Bulletin, 75(1):125–145.

Risso, A.

1810.   Ichthyologie de Nice, ou Histoire Naturelle des Poissons du Department des Alpes Maritimes. Pages i–xxvi, 1–388. Paris.

Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea, and W.B. Scott

1980.   A List of Common and Scientific Names of Fishes from the United States and Canada. Fourth edition, 174 pages. Bethesda, Maryland: American Fisheries Society Special Publication.

Robison, B.H.

1972.   Distribution of the Midwater Fishes of the Gulf of California. Copeia, 1972(3):448–461.

Robison, B.H., and T.G. Bailey

1981.   Sinking Rates and Dissolution of Midwater Fish Fecal Matter. Marine Biology, 65:135–142.

Robison, B.H., and J.E. Craddock

1983.   Mesopelagic Fishes Eaten by Fraser's Dolphin, Lagenodelphus hosei. Fishery Bulletin, 81(2):283–289.

Rochford, D.J.

1964.   Salinity Maxima in the Upper 1000 Metres of the North Indian Ocean. Australian Journal of Marine and Freshwater Research, 15(1):1–24.

1966a. Source Regions of Oxygen Maxima in Intermediate Depths of the Arabian Sea. Australian Journal of Marine and Freshwater Research, 17:1–30.

1966b. Distribution of Banda Intermediate Water in the Indian Ocean. Australian Journal of Marine and Freshwater Research, 17:60–76.

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1974.   Observations of the Diurnal Vertical Migrations of an Oceanic Animal Community. Marine Biology, 28:99–113.

Rubies, P.

1985.   Zoogeography of the Lanternfishes (Osteichthyes, Myctophidae) of Southwest Africa. In C. Bas, R. Margalef, and P. Rubies, editors, Simposio International Sobre las Areas de Alfloramiento mas Importantes del Oeste Africano (Cabo Blanco y Benguela), 1:573–586. Barcelona: Instituto de Investigacione Pesqueras.

Sawada, Y.

1983–1985. Lampanyctus regalis (Gilbert). In K. Amaoka, K. Nakaya, H. Araya, and T. Yasui, editors, Fishes from the North-Eastern Sea of Japan and the Okhotsk Sea off Hokkaido, 1983:90–91, 1985:236–237, 318. Tokyo: Japanese Fisheries Resource Conservation Association.

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1988.   Atlantic Fishes of Canada. Canadian Bulletin of Fisheries and Aquatic Sciences, 219: 731 pages.

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1949.   Sea Fishes of Southern Africa. 550 pages. Cape Town, South Africa: Central News Agency, Ltd.

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1985.   Towing Large Nets by Single Warp at Abyssal Depths: Methods and Biological Results. Deep Sea Research, 32(2):183–200.

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1996.   Basal Ctenosquamate Relationships and the Interrelationships of the Myctophiform (Scopelomorph) Fishes. In M.L.J. Stiassny, L.R. Parenti, and G.D. Johnson, editors, Interrelationships of Fishes, pages 405–426. New York: Academic Press.

Sverdrup, H.V., M.W. Johnson, and R.H. Fleming

1942.   The Oceans, Their Physics, Chemistry and General Biology. 1087 pages. New York: Prentice-Hall.

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1928.   Synopsis of the Scopelids in the North Atlantic. Videnskabelige Meddelelser fra Dansk Naturhistorisk Forening i Kjøbenhavn, 86:4–69.

1932.   Teleostei: Iniomi-Myctophidae. In L. Joubin, editor, Faune Ichtyologique Atlantique Nord, pages 109–128. Copenhagen.

Willis, J.M.

1984.   Mesopelagic Fish Faunal Regions of the Northeast Pacific. Biological Oceanography, 3:167–185. [Not seen; fide H.G. Moser.]

Willis, J.M., and W.G. Pearcy

1982.   Vertical Distribution and Migration of Fishes of the Lower Mesopelagic Zone off Oregon. Marine Biology, 70:87–98.

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1988.   Zoogeography of Midwater Fishes in the Subarctic Pacific. Bulletin of the Ocean Research Institute of the University of Tokyo, 26(2):79–142.

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1971.   Eight New Species of Myctophid Fishes from the Eastern Pacific Ocean. Copeia, 1971(1):39–54.

1974.   Description of Five New Species of Myctophid Fishes from the Pacific, Indian and Atlantic Oceans. Occasional Papers of the California Academy of Sciences, 110:1–37.

1976.   The Taxonomy and Distribution of Lanternfishes (Family Myctophidae) of the Eastern Pacific Ocean. Volume 3, 229 pages. Bay St. Louis, Mississippi: Naval Ocean Research and Development Activity.

Wyrtki, K.

1971.   Oceanographic Atlas of the International Indian Ocean Expedition. Pages i–xxi, 1–531. Washington, D.C.: National Science Foundation, U.S. Government Printing Office. No. 3800–0104.

Yang, J., Z. Huang, S. Cheng, and Q. Li

1996.   [The Deep-Water Pelagic Fishes in the Area from Nansha Islands to the Northeast Part of South China Sea.] 190 pages. Beijing: Science Press. [In Chinese; not seen; fide J.R. Paxton.]

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Manuscripts intended for series publication receive substantive review (conducted by their originating Smithsonian museums or offices) and are submitted to the Smithsonian Institution Press with Form SI-36, which must show the approval of the appropriate authority designated by the sponsoring organizational unit. Requests for special treatment—use of color, foldouts, case-bound covers, etc.—require, on the same form, the added approval of the sponsoring authority.

Review of manuscripts and art by the Press for requirements of series format and style, completeness and clarity of copy, and arrangement of all material, as outlined below, will govern, within the judgment of the Press, acceptance or rejection of manuscripts and art.

Copy must be prepared on typewriter or word processor, double-spaced, on one side of standard white bond paper (not erasable), with 1art″ margins, submitted as ribbon copy (not carbon or xerox), in loose sheets (not stapled or bound), and accompanied by original art. Minimum acceptable length is 30 pages.

Front matter (preceding the text) should include: title page with only title and author and no other information; abstract page with author, title, series, etc., following the established format; table of contents with indents reflecting the hierarchy of heads in the paper; also, foreword and/or preface, if appropriate.

First page of text should carry the title and author at the top of the page; second page should have only the author's name and professional mailing address, to be used as an unnumbered footnote on the first page of printed text.

Center heads of whatever level should be typed with initial caps of major words, with extra space above and below the head, but no other preparation (such as all caps or underline, except for the underline necessary for generic and specific epithets). Run-in paragraph heads should use period/dashes or colons as necessary.

Tabulations within text (lists of data, often in parallel columns) can be typed on the text page where they occur, but they should not contain rules or numbered table captions.

Formal tables (numbered, with captions, boxheads, stubs, rules) should be submitted as carefully typed, double-spaced copy separate from the text; they will be typeset unless otherwise requested. If camera-copy use is anticipated, do not draw rules on manuscript copy.

Taxonomic keys in natural history papers should use the aligned-couplet form for zoology and may use the multi-level indent form for botany. If cross referencing is required between key and text, do not include page references within the key, but number the keyed-out taxa, using the same numbers with their corresponding heads in the text.

Synonymy in zoology must use the short form (taxon, author, year:page), with full reference at the end of the paper under “Literature Cited.” For botany, the long form (taxon, author, abbreviated journal or book title, volume, page, year, with no reference in “Literature Cited”) is optional.

Text-reference system (author, year:page used within the text, with full citation in “Literature Cited” at the end of the text) must be used in place of bibliographic footnotes in all Contributions Series and is strongly recommended in the Studies Series: “(Jones, 1910:122)” or “…Jones (1910:122).” If bibliographic footnotes are required, use the short form (author, brief title, page) with the full citation in the bibliography.

Footnotes, when few in number, whether annotative or bibliographic, should be typed on separate sheets and inserted immediately after the text pages on which the references occur. Extensive notes must be gathered together and placed at the end of the text in a notes section.

Bibliography, depending upon use, is termed “Literature Cited,” “References,” or “Bibliography.” Spell out titles of books, articles, journals, and monographic series. For book and article titles use sentence-style capitalization according to the rules of the language employed (exception: capitalize all major words in English). For journal and series titles, capitalize the initial word and all subsequent words except articles, conjunctions, and prepositions. Transliterate languages that use a non-Roman alphabet according to the Library of Congress system. Underline (for italics) titles of journals and series and titles of books that are not part of a series. Use the parentheses/colon system for volume (number):pagination: “10(2):5–9.” For alignment and arrangement of elements, follow the format of recent publications in the series for which the manuscript is intended. Guidelines for preparing bibliography may be secured from Series Section, SI Press.

Legends for illustrations must be submitted at the end of the manuscript, with as many legends typed, double-spaced, to a page as convenient.

Illustrations must be submitted as original art (not copies) accompanying, but separate from, the manuscript. Guidelines for preparing art may be secured from the Series Section, SI Press. All types of illustrations (photographs, line drawings, maps, etc.) may be intermixed throughout the printed text. They should be termed Figures and should be numbered consecutively as they will appear in the monograph. If several illustrations are treated as components of a single composite figure, they should be designated by lowercase italic letters on the illustration; also, in the legend and in text references the italic letters (underlined in copy) should be used: “Figure 9b.” Illustrations that are intended to follow the printed text may be termed Plates, and any components should be similarly lettered and referenced: “Plate 9b.” Keys to any symbols within an illustation should appear on the art rather than in the legend.

Some points of style: Do not use periods after such abbreviations as “mm, ft, USNM, NNE.” Spell out numbers “one” through “nine” in expository text, but use digits in all other cases if possible. Use of the metric system of measurement is preferable; where use of the English system is unavoidable, supply metric equivalents in parentheses. Use the decimal system for precise measurements and relationships, common fractions for approximations. Use day/month/year sequence for dates: “9 April 1976.” For months in tabular listings or data sections, use three-letter abbreviations with no periods: “Jan, Mar, Jun,” etc. Omit space between initials of a personal name: “J.B. Jones.”

Arrange and paginate sequentially every sheet of manuscript in the following order: (1) title page, (2) abstract, (3) contents, (4) foreword and/or preface, (5) text, (6) appendices, (7) notes section, (8) glossary, (9) bibliography, (10) legends, (11) tables. Index copy may be submitted at page proof stage, but plans for an index should be indicated when the manuscript is submitted.