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SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES • NUMBER 20

Systematics and Ecology of the Sea-Urchin
Genus Centrostephanus (Echinodermata:
Echinoidea) from the Atlantic and
Eastern Pacific Oceans

David L. Pawson
and John E. Miller

SMITHSONIAN INSTITUTION PRESS
City of Washington
1983

ABSTRACT

Pawson, David L., and John E. Miller. Systematics and Ecology of the Sea-Urchin Genus Centrostephanus (Echinodermata: Echinoidea) from the Atlantic and Eastern Pacific Oceans. Smithsonian Contributions to the Marine Sciences, number 20, 15 pages, 5 figures, 5 tables, 1983.—Surveys by the Johnson-Sea-Link submersibles have revealed the presence of large populations of black Centrostephanus, superficially resembling Diadema antillarum Philippi, along the shelf edge prominences off the east coast of Florida in depths of 48–80 meters. Typical habitats are aggregations of dead coral rubble, with seasonal growths of leafy red algae. Some aspects of the biology of these echinoids are described.

We affirm that only a single species of the genus, Centrostephanus longispinus (Philippi), occurs in the Atlantic Ocean. As Fell (1975) and Serafy (1979) have shown, western Atlantic populations can be referred to the subspecies Centrostephanus longispinus rubicingulus H.L. Clark, which usually differs from the typical subspecies in possessing uniformly black spines rather than banded purple and yellowish white spines when fully grown. C. besnardi Bernasconi from Isla Trindade, Brazil, is herein synonymized with C. longispinus rubicingulus. C. coronatus (Verrill) from California and the Galapagos Islands differs little from C. longispinus and the two species may yet prove to be subjective synonyms. There is some evidence to suggest that Gulf of California populations of C. coronatus differs from California populations at the subspecies level.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution’s annual report, Smithsonian Year. SERIES COVER DESIGN: Seascape along the Atlantic coast of eastern North America.

Library of Congress Cataloging in Publication Data

Pawson, David L. (David Leo), 1938–

Sea urchin genus Centrostephanus (Echinodermata: Echinoidea)

(Smithsonian contributions to the marine sciences ; no. 20)

Bibliography: p.

Supt. of Docs, no.: ST 1.41:20

1. Centrostephanus. 2. Echinodermata—Atlantic Ocean. 3. Echinodermata—Pacific Ocean. I. Miller, John E. II. Title. III. Series.

QL384.E2P38    1983    593.9′5    83–600054

Systematics and Ecology of the Sea-Urchin
Genus Centrostephanus (Echinodermata:
Echinoidea) from the Atlantic and
Eastern Pacific Oceans

David L. Pawson and John E. Miller

David L. Pawson, Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560. John E. Miller, Harbor Branch Foundation, Inc., R.R. 1, Box 196, Fort Pierce, Florida, 33450.

Introduction

During investigations of the structure and faunas of shelf-edge prominences along the east coast of Florida (see Avent et al., 1977; Reed, 1980), a long-spined black sea urchin was found to be a notable and numerous inhabitant of coral rubble zones. Using Harbor Branch Foundation, Inc. submersibles Johnson-Sea-Link I and II, we have been able to collect specimens of this urchin, to observe them in their natural habitat, and maintain them alive in aquaria. Closer examination revealed that the urchin is a species of Centrostephanus, a widespread Atlantic and Indo-Pacific diadematid genus.

In this paper we describe this newly found material of Centrostephanus and discuss some aspects of its biology and systematic position. In addition, we compare our Florida specimens with C. longispinus from the eastern Atlantic and C. coronatus from the eastern Pacific.

ACKNOWLEDGMENTS.—Determinations of algal species were kindly made by S.M. Blair, Harbor Branch Foundation. We thank F.M. Bayer, Smithsonian Institution, for his helpful insight with several nomenclatural problems. Loan of museum specimens was made possible by Robert M. Woollacott, Museum of Comparative Zoology, Harvard, and Alberto Larrain, Allan Hancock Foundation, University of Southern California. We are indebted to the crews of Johnson-Sea-Link submersibles and R/V Johnson for their professional skills during submersible operations. We are grateful to G. Hendler and R.L. Turner for critically reviewing the manuscript. Funding for this study was granted by the Smithsonian Institution and Harbor Branch Foundation, Inc. This paper represents Contribution No. 118 from the Smithsonian Marine Station at Link Port and Contribution No. 336 from Harbor Branch Foundation, Inc.

Centrostephanus Peters, 1855

DIAGNOSIS.—Like Diadema, but with buccal plates carrying spines and pedicellariae. Globiferous pedicellariae present.

TYPE-SPECIES.—Centrostephanus longispinus (Philippi).

COMPOSITION OF THE GENUS.—Centrostephanus currently comprises ten nominal species, widely distributed in the Atlantic and Indo-Pacific. In his monograph of the Echinoidea, Mortensen (1940) described eight species of Centrostephanus. Later, Bernasconi (1955a,b) described C. besnardi from Isla Trindade, Brazil, and Fell (1975) described C. sylviae from San Felix and Juan Fernandez Islands, off Chile. Mortensen (1940) noted that C. longispinus and C. rubicingulus were apparently closely related; he believed that C. rubicingulus could be distinguished from C. longispinus by the presence in the former species of more numerous and larger secondary interambulacral tubercles. Fell (1975) briefly reviewed the genus and found that differences in size and number of secondary interambulacral tubercles were not reliable systematic characters. Fell (1975) suggested that C. rubicingulus should be reduced to a subspecies of C. longispinus, and he noted that the three nominal Atlantic Ocean species, C. longispinus, C. rubicingulus, and C. besnardi, along with juvenile C. coronatus from the eastern Pacific, “cannot be distinguished morphologically using adult characters. Identifications must be done by locality” (Fell, 1975:181). Serafy (1979) followed Fell’s suggestion, and reduced C. rubicingulus to a subspecies of C. longispinus (Phillippi).

FIGURE 1.—Relationship of apical system to horizontal diameter (in mm) in species of Centrostephanus (closed circles = C. longispinus longispinus (Philippi) from eastern Atlantic; open circles = C. longispinus rubicingulus H.L. Clark from east coast of Florida; closed triangles = C. coronatus (Verrill) from lower California coast; open triangles = C. coronatus from Gulf of California).

CLAVIFORM SPINES IN Centrostephanus.—Several authors, including Hamann (1887), Mortensen (1940), and Fell (1975) have called attention to the presence of peculiar club-shaped spines on the adapical plates in some species of Centrostephanus. These highly motile spines, tipped with an intense pink or purple pigment, are found in only four of the ten nominal species: C. longispinus, C. rubicingulus, C. besnardi, and C. coronatus. These closely related “species” form a natural (Tethyan″) group occurring in the eastern Atlantic, the western Atlantic, and in the eastern Pacific. Fell (1975) noted that C. asteriscus Agassiz and Clark, 1907, from Hawaii and the Kei Islands, has some features in common with the species mentioned above but differs in lacking claviform spines. Fell (1975) referred the species that lack claviform spines, C. rodgersii (Agassiz, 1863), C. tenuispinus Clark, 1914, and C. sylviae Fell, 1975, to a single “superspecies.” If the genus Centrostephanus were to be split into two genera or subgenera based upon the presence or absence of claviform spines, the genus name Trichodiadema Agassiz, 1863, type-species rodgersii Agassiz, is available for species that lack these spines.

FIGURE 2.—Relationship of whorls of spinelets of spines (verticillations) to horizontal diameter of test in species of Centrostephanus (circles = C. coronatus from Gulf of California; triangles = C. coronatus from lower California coast; squares = C. longispinus rubicingulus from east coast of Florida; open symbols = ambulacral spines; closed symbols = adambulacral spines).

CHANGES PROPOSED FOR THE GENUS Centrostephanus.—Results from our studies of live material and existing museum collections lead us to agree with the suggestions of Fell (1975). We accept Serafy’s reassignment of Centrostephanus rubicingulus to a subspecies of C. longispinus, although the diagnoses of the subspecies require some modification. Further, we refer C. besnardi Bernasconi to synonymy with C. longispinus rubicingulus H.L. Clark, thereby restricting Centrostephanus to eight nominal species.

Centrostephanus longispinus (Philippi)

DIAGNOSIS.—Claviform spines present adapically. Apical system usually 30%–40% of test diameter. Spines usually with well-developed trabeculae between wedges. Eastern and western Atlantic Ocean.

REMARKS.—Two subspecies of C. longispinus may now be recognized.

Key to Subspecies of C. longispinus

Centrostephanus longispinus longispinus (Philippi)

FIGURE 1; TABLE 1

Diadema longispina Philippi, 1845:354.

Centrostephanus longispinus.—Mortensen, 1940:300, pl. 24: figs. 1–11; pl. 25: figs. 11, 12; pl. 75: figs. 5–24 [complete synonymy up to 1938]; 1951:296.—Tortonese, 1953:214; 1965:311, figs. 143–145; 1976:238.—Chapman, 1955: 399.—Cherbonnier, 1956:17; 1959:44, pl. 4: figs, B-L; pl. 5: figs, a, b; 1963:186.—Millott, 1957, fig. 4.—Repelin, 1962:4, pl. 1: fig. 6; pl. 2: figs. 7, 8.—Chesher, 1966:215.—Märkel, 1970:190, figs. 1, 2, 4, 5, 14a.

?Centrostephanus longispinus.—Alvardo and Alvarez, 1964: 278.

MATERIAL EXAMINED.—Universitetets Zoologiske Museum, Copenhagen, Atlantide Expedition, Sta. 61, 106, 116, Gulf of Guinea, 53–95 meters, seven specimens. Museum of Comparative Zoology, Harvard University, Cat. No. 689, 4573, Northeastern Atlantic, two specimens.

DIAGNOSIS.—Spines banded purple and yellowish white. Mediterranean and eastern Atlantic.

TYPE-LOCALITY.—Palermo, Sicily.

DESCRIPTION.—Specimens examined were typical of the subspecies as described by Mortensen (1940) and others. Information on numbers of test plates, diameter of apical system and peristome, and on structure of spines, is presented in Table 1.

DISTRIBUTION.—Western Mediterranean; eastern Atlantic, from Morocco to Gabon; Cape Verde Islands and the Azores (Mortensen, 1940, 1951; Chesher, 1966). Depth range 42–208 meters.

REMARKS.—This subspecies has been thoroughly described by Koehler (1895) and Mortensen (1904, 1940), and requires no further comment here. Unlike C. longispinus rubicingulus (see below), apparently no specimens with spines of a solid dark color have been found; in even the largest specimens the spines are banded.

Centrostephanus longispinus rubicingulus H.L. Clark

FIGURES 1–5; TABLES 2, 3

Centrostephanus rubicingulus H.L. Clark, 1921:108, pl. 1: figs. 1, 2.

Centrostephanus rubricingulus H.L. Clark, 1925:52.—Mortensen, 1940:308, pl. 36: figs. 3–6, 11, 12, pl. 76: figs. 10–12, 14–18, 22. —A.H. Clark, 1954:374.—Lewis, 1961:53.—Fell, 1975:180.

Centrostephanus besnardi Bernasconi, 1955a:92; 1955b:56, figs. 1–9, pl. 1: figs. 2, 6; pl. 7: fig. 2a–c.—Brito, 1962:5, pl. 3: fig. 2; 1968: 20, pl. 9: figs. 2, 3.—Tommasi, 1967:10, figs. 1, 2.

Centrostephanus longispinus rubricingulus.—Serafy, 1979:28, fig. 8

SPECIES NAME.—In his original description of this species, H.L. Clark (1921:108) spelled the species name as rubicingulus. In a footnote, Clark stated that the name was derived from “rubus = red + cingulus = a zone or band, in references to the banded spines.” Here Clark was in error, for rubus translates from Latin as a bramble or blackberry. In a later paper (Clark, 1925) he spelled the species-name as rubricingulus without comment, and every subsequent author has spelled the name as rubricingulus. Clark’s original spelling of the species name does not represent an incorrect original spelling in the sense of Article 32(c) of the International Code of Zoological Nomenclature (1961 edition). Clark made an incorrect transliteration and, according to the provisions of Article 32(a) (ii), this does not qualify as an inadvertent error; the original spelling must therefore be retained.

TABLE 1.—Measurements of Centrostephanus longispinus longispinus from the eastern Atlantic (Atl. = Atlantide Expedition stations; MCZ = Museum of Comparative Zoology, Harvard University; H.D. = horizontal diameter of test (in mm); Dia. = diameter; % H.D. = peristome or apical system diameter expressed as percentage of test diameter; Plates A and IA = number of plates in ambulacral and interambulacral columns, respectively; Wedges A and IA = number of wedges in ambital ambulacral and interambulacral spines, respectively)

MATERIAL EXAMINED.—The description given below is based upon study of numerous live and preserved specimens collected from the east coast of Florida (see Table 2). Representative specimens have been deposited at the National Museum of Natural History, Smithsonian Institution (USNM E28068, E28069), and the Indian River Coastal Zone Museum, Harbor Branch Foundation, Inc. (IRCZM 72:330, 72:331, 72:332, 72:333, 72:334).

DIAGNOSIS.—Smaller specimens with banded spines, bands reddish brown on a whitish ground color. Larger specimens, horizontal diameter > 25 mm, with uniformly blackish spines or banded spines, the bands brown on a lighter brown ground color. Western Atlantic.

TYPE-LOCALITY.—Off Barbados, British West Indies.

DESCRIPTION.—Characters of test and spines are similar to those described by Mortensen (1940) for C. rubicingulus, although supposed differences between C. longispinus and C. rubicingulus noted by Mortensen are apparently not significant, as pointed out by Fell (1975) and by the present authors (see “Remarks,” p. 11). Information on the numbers of test plates, the diameter of peristome and apical system, and on the structure of spines, is presented in Table 3.

In natural light, overall color of living specimens appears uniformly black, except for distinctively colored claviform spines and lighter colored bases of primary spines. Under artificial light, the apical system is reddish brown, madreporic plate darker. Anal funnel and spines on the periproct are dark brown. On the plates surrounding the apical system, the proximal portion is deep reddish brown; the distal portion and all other plates are lighter reddish brown. Thus a dark ring is formed around the apical system. Claviform spines are reddish brown proximally, tipped with intense pink or purple pigment. Primary and secondary spines are dark reddish brown to black; the bases of the primary spines are light reddish brown, uniformly flecked with brown pigment spots. The podia are dark brown when contracted, flecked with reddish brown pigment spots when expanded. The peristome is creamy white, except for triangular areas adjacent to ambs, which are flecked with light brown spots. The spines around the peristome are white, with light orange tips. The cleaned test is green to yellowish white.

FIGURE 3.—Upper and lower, Centrostephanus longispinus rubicingulus H.L. Clark, photographed from Johnson-Sea-Link submersible on sea floor off Sebastian, Florida, 27°49.7′N, 79°58.2′W, at 58 m (note dense aggregations of dead Oculina coral rubble in area).

FIGURE 4.—Centrostephanus longispinus rubicingulus H.L. Clark, from off Sebastian, Florida: upper, specimen of 48 mm horizontal diameter; lower, specimen of 34 mm horizontal diameter.

FIGURE 5.—Upper: Centrostephanus coronatus (Verrill), from Gulf of California, horizontal diameter 33 mm; lower: Centrostephanus longispinus rubicingulus H.L. Clark, light-colored form from Gulf of Mexico, horizontal diameter 37 mm (note banding of spines).

TABLE 2.—Geographic and bathymetric distribution of Centrostephanus longispinus rubicingulus off east central Florida, compiled from observations and collections by Johnson-Sea-Link submersibles

    Locality
       Coordinates

Depth (m)

Daytona Beach
28°57.7′N, 80°06.5′W

66–84

Cape Canaveral
28°30.0′N, 80°10.4′W

43

28°29.6′N, 80°01.2′W

70

28°29.6′N, 80°06.5′W

51

28°29.5′N, 80°01.7′W

48

Satellite Beach
28°08.6′N, 79°59.6′W

73

Sebastian
27°50′11.7″N, 79°57′59.8″W

79

27°50′02.4″N, 79°58′08.3″W

67

27°49.7′N, 79°58.2′W

53–58

27°46′07.7″N, 79°58′10.5″W

85

27°46.0′N, 79°58.6′W

54

27°43.8′N, 79°58.4′W

60–70

27°43.8′N, 79°58.0′W

73

St. Lucie Inlet
27°12.5′N, 80°08.2′W

40

In the USNM collections are several lots of small (<20 mm h.d.) specimens of this subspecies; all have reddish brown bands on white ground color on their primary spines. Two additional specimens, one of 32 mm h.d. from Sebastian, Florida, and one of 37 mm h.d. from the Gulf of Mexico, also have distinctly light-colored, banded spines, although in these cases the bands are darker brown on a lighter brown ground color. It is possible that the black-spined adults are derived from younger specimens with banded spines, as in Diadema species (Mortensen, 1940). Alternatively it is possible that populations of specimens with banded spines occur elsewhere in the Florida-Caribbean area, and they have yet to be adequately sampled.

Concerning the black color of the spines in the east Florida specimens, one of us (J.E.M.) has noted that when these spines are immersed in liquid bleach, the black pigment disperses, and it becomes evident that the spines are banded with light and dark brown bands. In the field, occasional specimens have a very light-colored aboral surface and spines. In light of recently published information, (Weber and Dambach, 1972), on ameboid movement of pigment cells in C. longispinus longispinus, a study of the pigmentation of this western Atlantic form would undoubtedly be rewarding.

DISTRIBUTION.—Western Atlantic, from Florida to Brazil and Gulf of Mexico, 33–310 meters. Black, long-spined echinoids, usually referred to as “Diadema” (those collected or photographed in depths greater than 40 meters along the U.S. east coast from North Carolina to Florida), probably also represent this subspecies.

HABITAT.—Serafy (1979) found Centrostephanus longispinus rubicingulus on algal substrata (Lithothamnion spp.) in the Gulf of Mexico off Egmont Key and Sanibel Island, 55–73 m. During this study we examined specimens collected from shelf-edge prominences off east central Florida, from Daytona Beach to St. Lucie Inlet, 40–85 m (see Table 2). Many of these outcroppings are covered with a dense layer of rubble, remains of the reef-building scleractinian coral, Oculina varicosa Lesueur. In addition to Centrostephanus, these rubble zones support a rich and diverse invertebrate fauna of mollusks, echinoderms, polychaetes, decapods, and encrusting organisms (see Avent et al., 1977; Reed, 1980; Reed et al., 1982). Reed (1980) mapped numerous Oculina reefs, both living and dead, that occur off east central Florida in depths of 50–100 m. Our in situ observations of C. longispinus rubicingulus with the submersibles confirm that this subspecies is restricted to dead reefs.

TABLE 3.—Measurements of Centrostephanus longispinus rubicingulus from western Atlantic (first 11 specimens with uniformly blackish spines, last 4 with banded spines; abbreviations as in Table 1; also Whorls A and IA = number of whorls per 1 cm of spine length in ambulacral and interambulacral spines, respectively)

Several possibilities could explain the absence of Centrostephanus from living reefs. Living Oculina reefs support large schools offish that seek shelter within the confines of the reef matrix. Predation pressure by these fish, as well as the suspension-feeding coral polyps, may exclude juvenile and larval Centrostephanus respectively. Alternatively, the lack of suitable substratum for the settlement and metamorphosis of urchin larvae (i.e., living coral branches) might limit recruitment. In addition the living coral community provides less available space for the attachment of leafy algae and encrusting organisms, thereby limiting potential food resources for the urchins; leafy algae have not been reported from living Oculina reefs (J. Reed, pers. comm.).

As noted by Avent et al. (1977), C. longispinus rubicingulus usually occurs on the summits and sides of dead Oculina reefs. Though the bases of these reefs commonly extend to a depth of 100 m, Centrostephanus restricts its depth to 75–80 m, in apparent response to a distinct pycnocline and thermocline occurring at that depth.

POPULATION DENSITIES.—Throughout the year, C. longispinus rubicingulus were found in densities up to 5 individuals per m². Commonly co-existing with Centrostephanus are large populations of the cidaroid urchin, Stylocidaris affinis (Philippi), which achieves densities up to 80–100 individuals per m².

BEHAVIOR.—Laboratory-maintained specimens are photo-negative. A sudden increase or decrease of illumination evokes a rapid response of the primary spines that normally wave or rotate incessantly. The small claviform spines are especially sensitive to varying light intensities. Under intense artificial light from a fiber optics illuminator, the claviform spines initially wave vigorously and cease all movement after approximately 10 minutes. Reduction of light intensity induces resumption of normal movement.

Any slight mechanical stimulation also elicits a rapid reflex action, presumably defensive in nature. Similar reactions have been noted by von Uexkull (1896) in C. longispinus longispinus.

FEEDING.—In contrast to its congener, C. coronatus, which hides in crevices during the daylight and emerges only at night to feed (Nelson and Vance, 1979), C. longispinus rubicingulus actively forages in daylight. The coral rubble habitat of adult C. longispinus rubicingulus provides little refuge from predators, although juveniles perhaps receive some protection in the rubble.

During the months of June through September, various species of leafy algae have been observed attached to the coral rubble substratum. An examination of intestine contents of resident Centrostephanus revealed the remains of several of these species of red algae:

RHODOPHYTA

DELESSERIACEAE

Searlesia subtropica (Schneider) Schneider and Eiseman

Apoglossum ruscifolium (Turner) J. Agardh

Hypoglossum tenuifolium (Harvey) J. Agardh

Nitophyllum species

KALLYMENIACEAE

Kallymenia limminghii Montagne

RHODYMENIACEAE

Leptofauchea rhodymenioides Taylor

Diet during those months in which leafy algae is absent is unknown. However, the presence year-round of large, successful populations of urchins suggests that C. longispinus rubicingulus can also exist on a varied diet of small invertebrates, encrusting organisms, and drift algae. Vance (1979) reported a similar diet for C. coronatus off Catalina Island, California.

In the laboratory, we have maintained several specimens in closed-system aquaria for up to two years. These specimens fed on fresh shoots of the seagrass Thalassia testudinum. Starved specimens have been observed to prey upon the arms of the sea star Narcissia trigonaria Sladen.

SEXUAL DIMORPHISM.—In specimens of Florida C. longispinus rubicingulus, males possess conspicuous tubular genital papillae while females have short conical papillae. Through a brief survey of museum specimens, we were able to determine that the following species of Centrostephanus also display this type of sexual dimorphism: C. longispinus longispinus (Philippi), C. rodgersii (A. Agassiz), and C. coronatus (Verrill). It is probable that all species in the genus are sexually dimorphic. This type of sexual dimorphism is probably more common among echinoids than formerly supposed (Chia, 1977; Pawson and Miller, 1979).

REMARKS.—In commenting on C. rubicingulus, Mortensen (1940:310) noted the “general resemblance to longispinus in nearly all characters.” He listed several supposed differences in the interambulacral tubercle size and distribution, in the number of wedges in primary spines, and in the tridentate and ophicephalous pedicellariae. As examination of our newly acquired material of C. longispinus rubicingulus demonstrates, the only consistent difference, at least in adult specimens, lies in the one character that Mortensen (1940) dismissed, namely the coloration of spines.

Bernasconi (1955a,b) based her species C. besnardi on two small specimens, h.d. 12 and 18 mm, from Isla Trindade, off Brazil. In her detailed description, Bernasconi noted that C. besnardi differs from C. longispinus in various characters of the apical system, the rostrate pedicellariae, and the spine coloration. In the apical system of C. besnardi, ocular plates are all exsert, and the plates are essentially naked, except for the presence of a single secondary tubercle. According to Mortensen (1940:303), the position of the ocular plates, either insert or exsert, as well as the tuberculation of the apical system plates, can vary considerably in C. longispinus. The rostrate pedicellariae of C. longispinus are also variable in shape (Mortensen, 1940:305). Bernasconi’s description (1955b:59) and figures of rostrate pedicellariae do not provide a clear indication that the rostrate pedicellariae of C. besnardi are distinctive. Coloration of the spines in C. besnardi (white and claret colored bands) seem to differ in no important aspect from that in juvenile C. longispinus rubicingulus. Although type specimens of this species are not available for study, it seems evident that C. besnardi falls within the range of variation of C. longispinus rubicingulus, and the species are herein regarded as synonymous. Fell (1975) has already suggested that C. besnardi might be at best a subspecies of C. longispinus.

TABLE 4.—Measurements of Centrostephanus coronatus, from lower California (see Tables 1 and 3 for abbreviations; also, AHF = Allan Hancock Foundation)

Centrostephanus coronatus (Verrill)

FIGURES 1, 2, 5; TABLES 4, 5

Echinodiadema coronata Verrill, 1867:295.

Centrostephanus coronatus.—Mortensen, 1940:314, pls. 36: figs. 7–10, pl. 76: figs. 1–4 [complete synonymy up to 1938].—H.L, Clark, 1948:237, 244, pl. 39: fig. 10.—Fell, 1975:181.—Morris, Abbott, and Haderlie, 1980:162, pl. 51: fig. 11.2a,b.

MATERIAL EXAMINED.—Allan Hancock Foundation, University of Southern California: Lower California (6.30, 8.34, 8.36, 8.38, 8.43), eight specimens; Gulf of California (8.27, 8.28), six specimens. National Museum of Natural History, Smithsonian Institution: Gulf of California (USNM 17441, USNM 32472), five specimens.

DIAGNOSIS.—Like Centrostephanus longispinus, except that diameter of apical system usually 24%–34% of test diameter. Spines may virtually lack trabeculae between wedges.

TYPE-LOCALITY.—Cabo San Lucas, Gulf of California.

DISTRIBUTION.—Mortensen (1940) noted that C. coronatus was known only from the Gulf of California to 3 fathoms. The species also occurs at the Galapagos Islands and in lower California (including offshore islands) where it is common in depths of 3–10 meters (H.L. Clark, 1948; see Pearse, 1972).

REMARKS.—H.L. Clark (1921:109) noted that “in every way” his C. rubicingulus is nearest to C. coronatus. Mortensen (1940:310) disagreed, and later (p. 315, et seq.) alluded to differences in characters of test, spines, pedicellariae, and color that could distinguish C. coronatus from C. longispinus. Our investigations of additional material revealed the following information.

In examining the interambulacra, Mortensen (1940:317) noted that in C. coronatus only the uppermost interambulacral plates carry claviform spines, whereas in C. longispinus “…the two uppermost plates often carry a claviform spine, and are without a primary tubercule….” In our material of C. longispinus, more often than not, there is only a single adapical interamb plate with a claviform spine, Furthermore, in C. coronatus, several instances occur in which the two uppermost interamb plates carry claviform spines. Thus, this character is not reliable.

Regarding the apical system, Mortensen (1940) stated that in C. coronatus the apical system is 25%–27% of the horizontal diameter, while in C. longispinus it is 35%–40%. Our material shows that in C. coronatus the apical system is 24%–34% h.d., while in C. longispinus it is 31%–40% h.d. (see Tables 1, 3, 4, and 5; Figure 1). There is a slight overlap in these proportions, but apical system sizes do appear to differ consistently in the two “species.”

TABLE 5.—Measurements of Centrostephanus coronatus, from Gulf of California (see Tables 1 and 3 for abbreviations; also, USNM = United States National Museum, collections in National Museum of Natural History, Smithsonian Institution; Mrtsn. = Mortensen collection; AHF = Allan Hancock Foundation)

Supposed differences in spine coloration, noted by Mortensen (1940), are eliminated by our new Florida material. In large specimens of C. coronatus, the spines are nearly black and the same is true for C. longispinus rubicingulus, at least in East Florida populations. One usually consistent difference between the two species lies in the trabecules between the spokes of the spines; in C. longispinus trabecules are conspicuous, while in C. coronatus they are virtually non-existent (Mortensen, 1940).

The number of verticillations (whorls of spinelets) on the spines provide some evidence that there may be two distinct subspecies of C. coronatus (see Tables 4 and 5; Figure 2). In Gulf of California specimens, the number of verticillations in ambulacral and interambulacral spines usually exceeds 20 per cm of spine length; in California specimens examined, there are usually fewer than 20 verticillations per cm of spine length. A more detailed survey of California specimens from several habitats is required before the status of the California and Gulf of California populations is settled. In C. longispinus rubicingulus spines usually have fewer than 20 whorls of spinelets per cm of spine length, and thus in this character the western Atlantic Centrostephanus most closely resembles the California coast populations of C. coronatus.

The relatively trivial differences between C. coronatus and C. longispinus might seem to justify uniting them under a single species name. We hesitate to take this step because it would appear to serve no useful purpose. It is important to note, however, that these species are indeed closely related, contrary to Mortensen’s (1940) contentions.

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