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SMITHSONIAN CONTRIBUTION TO ZOOLOGY • NUMBER 174

Three New Crustaceans from La Media Luna, San Luis Potosí, Mexico

Alejandro Villalobos Figueroa and Horton H. Hobbs, Jr.

SMITHSONIAN INSTITUTION PRESS

City of Washington

1974

A B S T R A C T

Villalobos Figueroa, Alejandro, and Horton H. Hobbs, Jr. Three New Crustaceans from La Media Luna, San Luis Potosí, Mexico. Smithsonian Contributions to Zoology, number 174, 18 pages, 8 figures, 1 table, 1974.—Representatives of three families of crustaceans are described from La Media Luna, San Luis Potosí, Mexico: Ankylocythere barbouri representing the ostracod family Entocytheridae, Procambarus (Pennides) roberti, the decapod family Cambaridae, and Palaemonetes (Palaemonetes) lindsayi belonging to the decapod family Palaemonidae. All three are known only from the vicinity of the type-locality and seem to have affinities with species occurring in the southeastern part of the United States. A key to the freshwater representatives of the genus Palaemonetes, together with a summary of their diagnostic features, is appended.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 5080. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus).

Library of Congress Cataloging in Publication Data

Villalobos Figueroa, Alejandro.

Three new crustaceans from La Media Luna, San Luis Potosí, Mexico.

(Smithsonian contributions to zoology, no. 174)

Supt. of Docs, no.: SI 1.27:174.

1. Ankylocythere barbouri. 2. Procambarus roberti. 3. Palaemonetes lindsayi. 4. Crustacea—Mexico—San Luis Potosí (State). I. Hobbs, Horton Holcombe, 1914- joint author. II. Title. III. Series: Smithsonian Institution. Smithsonian contributions to zoology, no. 174.

QL1.S54 no. 174 [QL441.2] 591′.08s [595′.384] 74-879

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 Price 30 cents (paper cover)

Three New Crustaceans from La Media Luna, San Luis Potosí, Mexico

Alejandro Villalobos Figueroa and Horton H. Hobbs, Jr.

____________

Alejandro Villalobos Figueroa, Instituto de Biologia, Universidad Nacional Autónoma de México, Apartado Postal 70-233 México 20, D. F., México. Horton H. Hobbs, Jr., Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560.

Introduction

Three new crustaceans, a crayfish of the genus Procambarus, which harbors an entocytherid ostracod of the genus Ankylocythere, and a shrimp belonging to the genus Palaemonetes may now be added to the faunal list of aquatic animals frequenting the springs and drainage ditches of La Media Luna, San Luis Potosí.

The presence of the crayfish in this headwater tributary of Río Pánuco was discovered by Salvador Contreras on 15 June 1968, and a year later, Clyde D. Barbour collected a single female there, which he sent to the Smithsonian Institution. Being aware of the active fieldwork of Robert R. Miller in Mexico, we asked him to try to get additional specimens for us, should he be collecting in the area. To our delight, he and Kinji Kurawaka obtained seven specimens of the new crayfish, together with two shrimp. Dr. Contreras also secured five additional crayfish in December 1971. After it was realized that the shrimp represented an un-described species, the senior author visited La Media Luna where, on 14 February 1972, more than 500 additional shrimp were taken in canals and springs of Ejido Las Palomas.

Miller (1956), in describing the endemic cyprinodontid Cualac tessellatus from La Media Luna, presented the following account of the habitat:

La Media Luna is the name given to an extensive warm-spring area that lies in a broad meadow about seven airline miles south-southwest of the town of Río Verde. A large, constant volume of water rises principally from two rather deep holes in a crescent-shaped pond (laguna) and provides all the water for three muniripios. The approximate area of the laguna has been estimated to be 24,800 square meters…. The water is blue, very clear, and has a strong sulfur odor. Water temperatures taken at various stations during different seasons indicate a variation from about 83° to 86.5° F…. The pH varied from 6.9 to 7.3 … hardness was recorded as 92 p.p.m. of CaCO₃. There was no trace of CO₂ and no reaction to phenolphthalein. According to our altimeter, the elevation is 3,580 feet … the correct altitude of La Media Luna may be closer to 3,350 feet ….

The vegetation of the region is arid, with few trees on the valley floor and a close growth of xerophytic plants on the hills. Mesquite and creosote bush are characteristic, along with large acacias, yuccas, and numerous cacti. Principal crops are sugar cane, corn, beans, citrus fruits, and bananas …. Although the vegetation zone of the area is classified in a general way as desert … it is markedly different from the other desert areas of northeastern Mexico, and reflects the peculiar position of a depression lying between the relatively low crest (5,500 ft.) of the Sierra Madre Oriental, just to the east and the much higher ranges (8,000 ft.) to the west …. The mean annual rainfall of the depression may approach 15 to 20 inches.

In the field notes that accompanied the specimens received from Dr. Miller, he included the following additional information. The ditch (Figure 1) from which the material was collected was some 8 to 35 feet in width and situated in a cultivated area with few trees and shrubs along the bank. The moderately strong current of clear water (78°F) flowed over a bottom consisting of rocks, boulders, gravel, and deep mud, and supported dense beds of submergent aquatic plants, Scirpus, and a few water lilies. The crayfish and shrimp were taken by seine and hand net along the undercut bank at depths of two to three feet. The fishes secured in the same area included Astyanax fasciatus mexicanus (de Filippi), Dionda rasconis (Jordon and Snyder), Cichlasoma bartoni (Bean), Cichlasoma steindachneri Jordon and Snyder, Ataeniobius toweri (Meek), and the endemic Cualac tessellatus Miller. Only two other fishes, Ictalurus mexicanus (Meek) and Cichlasoma labridens (Pellegrin), are known to occur in the area.

ACKNOWLEDGMENTS.—We wish to thank Clyde D. Barbour, Salvador Contreras, Robert R. Miller, and Kinji Kurawaka for their kindness in collecting many of the specimens on which the descriptions are based. Dr. Miller also provided us with the photograph of the type-locality and read an early draft of the manuscript. We are also grateful to Isabel Pérez Farfante, Fenner A. Chace, Jr., and Margaret A. Daniel for their criticisms of the manuscript and to Ned E. Strenth for his critical reading of the key.

FIGURE 1.—Ditch from La Media Luna, San Luis Potosí, Mexico, the type-locality of Procambarus roberti, Palaemonetes lindsayi and Ankylocythere barbouri. (Photo courtesy of Robert R. Miller.)

Procambarus (Pennides) roberti, new species

FIGURE 2

DIAGNOSIS.—Body pigmented, eyes well developed. Rostrum with marginal spines. Areola 31.1 to 34.5 percent of entire length of carapace, and 7 to 10 times longer than wide. Two cervical spines usually present. Suborbital angle rounded and weak. Postorbital ridge with apical spine. Hepatic region tuberculate but lacking spines. Antennal scale approximately 2.3 times longer than wide, broadest near midlength. Ischia of third and fourth pereiopods of first form male with simple hooks overreaching basioischial articulation proximally. First pleopods of male asymmetrical, lacking cephalic shoulder, provided with conspicuous array of subterminal setae, and reaching coxae of third pereiopods; distal extremity bearing (1) slender, caudomesially situated mesial process extending caudodistally and somewhat laterally, slightly beyond other terminal elements; (2) small, curved, platelike, corneous cephalic process on cephalodistal surface; (3) subtriangular, laterally grooved, corneous caudal process on caudodistal surface abutting caudal base of centrally located central projection; and (4) corneous, central projection extending distally about same distance as cephalic process, slightly farther than caudal process, and consisting of subspatulate centrocephalic process and smaller subtriangular centrocaudal process. Annulus ventralis subspindle-shaped, broader than long, with broad median elevated portion marked by sigmoid sinus cutting caudal 0.8 length of annulus. Sternum immediately cephalic to annulus with few low tubercles, but with caudal margin entire.

HOLOTYPIC MALE, FORM I.—Body (Figure 2c,l) subovate, somewhat compressed laterally. Abdomen slightly narrower than thorax (10.3 and 11.5 mm). Width of carapace slightly less than height at caudodorsal margin of cervical groove (10.9 and 11.5 mm). Areola 7.4 times longer than broad with 2 punctations across narrowest part. Cephalic section of carapace 2.1 times as long as areola (latter 32.2 percent of entire length of carapace). Rostrum excavate dorsally with unthickened margins slightly convex at base and tapering to marginal spines; dorsal surface with submarginal row of setiferous punctations and others scattered between; spines at base of acumen moderately strong; acumen subtriangular, longer than wide between marginal spines (1.7 and 1.4 mm), and constituting approximately 25 percent of total length of rostrum. Subrostral ridges weak and scarcely evident in dorsal aspect. Postorbital ridges strong, grooved dorsolaterally, with setiferous punctations, and terminating cephalically in corneous-tipped spines. Suborbital angle very weak and rounded. Branchiostegal spine prominent and acute. Carapace punctate dorsally, with conspicuously large pits from base of rostrum posteriorly over most of gastric region; hepatic region mostly tuberculate; branchiostegites granulate laterally and with tubercles ventral to cephalic portion of cervical groove. Two cervical spines on each side of carapace subequal in size. Abdomen slightly longer than carapace (27.4 and 25.2 mm). Cephalic section of telson with 3 spines in each caudolateral corner. Epistome (Figure 2k) subcordiform, broader than long; well defined fovea present. Antennules of usual form with prominent spine on ventral surface of proximal segment near midlength. Antennae extending caudally to near midlength of telson. Antennal scale (Figure 2o) about 2.4 times longer than broad, broadest near midlength, with broadest lamellar area about 1.6 times wider than thickened lateral portion, latter terminating in strong acute spine.

Right chela (Figure 2p) moderately depressed, with palm somewhat inflated; lateral margin with row of subsquamous tubercles along proximal half; dorsal and ventral surfaces of palm with ciliated squamous tubercles, mesial margin with irregular row of 6 or 7 tubercles flanked dorsally by irregular row of 8, ventral surface with prominent tubercle opposite base of dactyl. Fixed finger with moderately well-developed median longitudinal ridge flanked by setiferous punctations, and proximomesial surface with several tuberosities; opposable margin with row of 8 rounded tubercles along proximal 0.6 subtended by row of conspicuously setiferous punctations, third and fourth tubercles from base largest, and large tubercle on lower level at base of distal third; crowded minute denticles along almost entire length, sublinearly arranged basally but forming broad band distally; ventral surface with submedian ridge, otherwise with setiferous punctations. Dactyl with low submedian longitudinal ridges dorsally and ventrally, flanked proximally by tubercles and distally by setiferous punctations; mesial surface with tubercles along proximal fourth and setiferous punctations distally; opposable margin with row of 9 low, rounded tubercles along proximal three-fifths, interspersed in band of crowded minute denticles extending almost entire length of finger.

FIGURE 2.—Procambarus (Pennides) roberti (a, c, e–g, i–l, o, p from holotypic male. Form I; b, d, h, m, n from morphotypic male, Form II): a, mesial view of first pleopod; b, mesial view of distal part of first pleopod; c, lateral view of carapace; d, caudoiateral view of distal part of first pleopod; e, lateral view of first pleopod; f, caudal view of first pleopods; g, annulus ventralis of allotype; h, dorsal view of cephalic region; i, basal podomeres of third, fourth, and fifth pereiopods; j, lateral view of first pleopod with pubescence; k, epistome; l, dorsal view of carapace; m, ventral view of basal podomeres of third, fourth, and fifth pereiopods; n, dorsal view of distal podomeres of cheliped; o, antennal scale; p, dorsal view of distal, podomeres of cheliped.

Carpus of right cheliped longer than broad (6.4 and 4.3 mm), with dorsal and dorsomesial surfaces tuberculate and that lateral to oblique furrow punctate; distal dorsomesial surface with prominent spine; mesial surface with 1 very large spine slightly distal to midlength and several small tubercles proximal to it; ventrodistal margin with 2 spines, 1 on ventral articular condyle and other submedian.

Merus of left cheliped mostly punctate; dorsal margin with row of tubercles along proximal half and more irregularly arranged ones distally, two subdistal ones spiniform; ventrolateral margin with row of 10 tubercles proximal to fork and 5 in each ramus of fork; ventromesial margin with row of 16 tubercles; distal tubercles in mesial and lateral rows strongly spiniform; other smaller tubercles present mesial and lateral to 2 rows. Ischium with row of 4 small tubercles on ventromesial margin.

Hooks on ischia of third and fourth pereiopods (Figure 2i) simple, and both overreaching basioischial articulation, neither opposed by conspicuous prominence on basis, instead by large pit, bearing tuft of setae; hook on third subconical and longer than somewhat flattened hook on fourth. Coxa of fourth pereiopod with prominent caudomesial boss; that of fifth with slender, rounded, subspatulate prominence on ventral caudomesial margin.

Sternum between second through fifth pereiopods moderately deep and bearing prominent fringe of setae on ventrolateral margins.

First pleopods (Figure 2a,e,f,j) as described in diagnosis.

ALLOTYPIC FEMALE.—Differing from holotype in following respects: acumen of rostrum subequal in length and width at base; postorbital spines longer; ventral members of paired cervical spines distinctly larger than dorsal ones; cephalic section of telson with only 2 spines in right caudolateral corner; epistome with paired anterolateral obtuse angles; opposable margin of both fingers of chela with minute denticles reduced to very narrow band, with maximum of 3 denticles in broadest portions; carpus of cheliped with small spiniform tubercle immediately proximal to large spine on dorsal mesiodistal angle, and with additional spiniform tubercles proximal to spine on mesial surface; several tubercles ventral to large spine also spiniform; ventral surface of merus with mesial row of 13 or 14 tubercles and lateral row of 9 or 11, with 2 or 3 in distomesial ramus of lateral row. (See “Measurements.”)

Sternum cephalic to annulus ventralis (Figure 2g) comparatively shallow, with caudal margin entire; surface of winglike plates between fourth pereiopods with few very low tubercles, otherwise unadorned.

Annulus ventralis freely movable, broader than long, subspindle-shaped in outline, with median portion elevated ventrally and bearing broadly S-shaped sinus, latter beginning on median line, approximately 0.2 length of annulus from cephalic margin, extending caudodextrad, then turning gently caudosinistrad to median line before bending slightly caudodextrad to caudal margin. Median sternite immediately caudal to annulus in form of half-ellipse, with horizontal caudal margin and with transverse elevation, highest medially, slightly cephalic to midlength.

First pleopods uniramous and reaching cephalic margin of annulus when abdomen flexed.

MORPHOTYPIC MALE, FORM II.—Differing from holotype in following respects: width of cephalothorax and abdomen 10.3 and 8.5 mm, respectively; width and height of cephalothorax at level of caudodorsal margin of cervical groove 10.3 and 9.5 mm, respectively; areola 4.9 times longer than broad; cephalic section of carapace twice as long as areola and constituting 33 percent of total length of carapace; surface of rostrum (Figure 2h) grooved and with fine punctations, marginal spines well defined, acumen triangular, length less than distance between spines (1.3 and 1.6 mm) and constituting 23.2 percent of total length of rostrum; postorbital ridge well defined, terminating anteriorly in spine; branchiostegal spine conical and sharp; only 1 cervical spine present; abdomen slightly longer than carapace (23.0 and 20.7 mm); antennal scale 2.4 times longer than wide and with greatest width at midlength; right chela (Figure 2n) slenderer than that of holotype and with opposable margins of fingers less pubescent, immovable finger with 6 small, somewhat hemispherical teeth along dorsal region of margin and 1 large subconical tubercle situated ventrally at base of distal 0.33 of dactyl, movable finger with 6 denticles; carpus of cheliped with 2 spines on mesial surface, 1 near midlength and other subdistal; ischia of third and fourth pereiopods (Figure 2m) with hooks represented by angular prominences.

First pleopod (Figure 2b,d) with mesial process conical, broad basally, and maintaining its caudomesial position; cephalic process forming broad plate; central projection consisting of subconical tubercle; caudal process absent.

COLOR.—Mostly bleached after several weeks’ preservation in formalin and alcohol; however, palm of chela reddish purple dorsally, reddish orange ventrally; fingers black dorsally and ventrally, with reddish orange tips. Distal half of merus and entire carpus reddish purple.

TYPE-LOCALITY.—“Ditch from La Media Luna, 4.8 miles (6.6 km) south of Río Verde (on highway to Pedro Montoya) and 2.5 miles (4 km) west on dirt road to Mina El Refugio, San Luis Potosí, México” (Miller, in litt.). See Figure 1 and “Introduction” for description.

DISPOSITION OF TYPES.—The holotypic male, Form I, allotype, and morphotypic male, Form II, are deposited in the National Museum of Natural History, Smithsonian Institution, under the catalog numbers of the United States National Museum (USNM), 132345, 132346, and 144826, together with 2 females and 1 juvenile female paratype. The remaining paratypes consisting of 4 males, Form I, 2 females, and 2 juvenile females are in the collections of the Instituto de Biologia, Universidad Nacional Autónoma de México.

RANGE AND SPECIMENS EXAMINED.—All of the specimens available are from Laguna de la Media Luna: 2art1, 9 km southwest of Río Verde, 15 June 1968, Salvador Contreras, coll.; 1art, type-locality, 9 June 1969, Clyde D. Barbour and R. J. Douglass, coll.; 2artI, 3art, 1 juv. art, type-locality, 8 March 1971, Robert R. Miller and Kinji Kurawaka, coll.; 1 art I, 1 art II, 1 art, 2 juv. art, 7 km southwest of Río Verde, 23 December 1971, F. C, coll.

SIZE AND VARIATION.—The largest specimen available is a paratypic first form male that has a carapace length of 29.6 mm, 4.4 mm longer than the holotype. The largest female, the allotype, has a corresponding length of 27.0 mm.

Most of the variations noted seem rather in-significant and some, at least, are associated with size and/or possible injury. Chief among them is the presence of only 1 cervical spine on each side in the largest male; all of the spines are heavier and more tubercle-like in this specimen than in any of the others. The epistome varies from subcordiform to subtriangular, some specimens having anterolateral angles. The number of tubercles along the mesial margin of the palm of the chela ranges from 6 to 8. The boss on the coxa of the left fifth pereiopod of the largest male consists of a broad plate rather than a subspatulate one as on the right pereiopod and in the holotype. The spines on the caudolateral corner of the cephalic section of the telson vary from 2 to 4. There may be 1 or 2 subdistal spines on the dorsal surface of the merus. The sinus on the annulus ventralis may be a mirrored image of that in the allotype and may also be more strongly curved.

RELATIONSHIPS.—Procambarus roberti is a member of the subgenus Pennides Hobbs (1972:10) and has its closest affinities with those crayfishes that have formerly been assigned to the Spiculifer Group (Ortmann, 1905:100). Among them (see Hobbs, 1969), it resembles most closely P. natchitochae Penn (1953:5), P. ablusus Penn (1963:121), P. elegans Hobbs (1969:329), and P. penni Hobbs (1951: 273). In all of them, the first pleopod of the first form male has a full complement of terminal elements, and the central projection is directed distally or subdistally. Too, the sternum immediately anterior to the annulus ventralis is not produced into tuberculiform or fingerlike lobes. It differs from all of the species of the subgenus in possessing an areola that is 7 to 10 times longer than wide; in none of the other members is it more than 6 times longer, and in most less than 5. It is the only member of the subgenus in which the cephalic process is in the form of a curved, corneous plate. This platelike cephalic process and the large punctations on the dorsal surface of the carapace, particularly between the postorbital ridges, are unique in the subgenus Pennides and resemble characteristics that are more typical of the members of the Mexican subgenus Villalobosus Hobbs (1972:12) (= “section riojae” Villalobos, 1955:94).

ETYMOLOGY.—This species is named in honor of Robert R. Miller, who has contributed greatly to our knowledge of the Mexican crayfishes by sending many collections to the Smithsonian and who made a special effort to obtain specimens of this new Mexican species.

MEASUREMENTS (mm).—

Ankylocythere barbouri, new species

FIGURE 3

DIAGNOSIS.—Shell length: art, 0.36 mm; art, 0.40-0.41 mm. Shell height: art. 0.19-0.20 mm; art, 0.22 mm.

Clasping apparatus with talon represented by very slight excrescence near midlength of external border of horizontal ramus; internal border with 2 teeth, larger tooth above talon and small one immediately distal to larger; apex with 2 upturned denticles. Ventral portion of peniferum subtruncate with anteroventral angle produced ventrally in short spinelike projection and with short fingerlike thickening at posterior end of truncate ventral extremity.

MALE.—Eye situated at anterodorsal 0.2 of shell. Shell (Figure 3e) oblong with greatest height slightly posterior to midlength; ventral margin only slightly curved, lacking concavity; submarginal setae almost evenly spaced except dorsally, and few additional setae on posterolateral surface.

Copulatory complex (Figure 3a-c) with peniferum slightly arched posteriorly, subtruncate ventrally, with short spinelike projection anteroventrally supported by elevated flange extending dorsally almost to level of penis; small fingerlike thickening directed anteriorly on posteroventral extremity. Penis much longer than half anteroposterior diameter of peniferum at level of penis and curved with proximal and distal ends directed at angle of approximately 130 degrees. Dorsal and ventral fingers moderately heavy and both terminating in simple setiform tips; ventral finger gently curved throughout its length. Clasping apparatus with indistinctly delimited horizontal and vertical rami disposed at angle of approximately 50 degrees. Pre- and postaxial borders of vertical ramus entire; postaxial border of horizontal ramus with slight excrescence near midlength (excrescence more clearly defined, with horizontal ramus directed somewhat laterally); preaxial border of horizontal ramus with 2 teeth: proximal one larger and situated opposite excrescence, smaller tooth located slightly distal to larger one and with distinct curved ridge extending proximoventrally from apex; distal extremity of ramus with 2 denticles directed somewhat dorsally.

FIGURE 3.—Ankylocythere barbouri: a, copulatory complex of paratypic male; b, c, clasping apparatus of same; d, lateral view of shell of allotypic female; e, lateral view of shell of holotype. (Scales in mm.)

TRIUNGUIS FEMALE (Figure 3d).—Eye situated anterodorsally at anterior 0.17 of shell length. Shell oblong, slightly higher in posterior half than in anterior, greatest height distinctly posterior to midlength; submarginal setae as in male.

Genital complex consisting of 2 posterodorsally situated elements: posterior one subdigitiform, hyaline, and grooved laterally; anterior sclerotized and cylindroid.

MEASUREMENTS.—Holotype: length 0.36 mm, height 0.20 mm. Allotype: length 0.41 mm, height 0.22 mm. See “Diagnosis” for ranges.

TYPE-LOCALITY.—Ditch from La Media Luna, 4.8 miles (6.6 km) south of Río Verde (on highway to Pedro Montoya) and 2.5 miles west on dirt road to Mina El Refugio, San Luis Potosí, Mexico. (See Figure 1 and “Introduction” for description).

DISPOSITION OF TYPES.—The type-series, consisting of the holotypic male, USNM 149159, allotypic female, USNM 149160, a dissected paratypic male, a paratypic female, and 6 juvenile specimens, is deposited in the National Museum of Natural History, Smithsonian Institution, under the catalog numbers of the United States National Museum (USNM). No other specimens are available.

RANGE AND HOST.—Known only from the type-locality, where it is the sole entocytherid infesting the crayfish Procambarus (Pennides) roberti, described above.

ETYMOLOGY.—This ostracod is named in honor of its discoverer, Clyde D. Barbour, who has contributed a number of Mexican crayfishes to the Smithsonian Institution.

RELATIONSHIPS.—Ankylocythere barbouri exhibits characteristics that indicate its close relationships with two geographic neighbors currently assigned to different genera: Ankylocythere toltecae Hobbs (1971:36) from the states of Hidalgo, San Luis Potosí, and Tamaulipas, and Uncinocylhere bicuspide (Rioja, 1943:565) from Hidalgo, Puebla, and Veracruz. It differs most strikingly from the former in possessing two teeth on the preaxial border of the horizontal ramus of the clasping apparatus of the male and from the latter in bearing a rudimentary talon (excrescence) on the postaxial border of the ramus (see Hobbs, 1971, for summaries of our knowledge of both species). Whereas the excrescence in A. toltecae is markedly reduced in size as compared with that of many members of the genus, it is even more rudimentary in A. barbouri. The latter differs from both in being larger; for example, its shell length in the male is 0.36 mm, whereas the corresponding lengths in A. toltecae and U. bicuspide range from 0.29 to 0.31 mm in both species. The penifera of the three are markedly similar, and the clasping apparatus are basically similar, differing essentially only in the characteristic pointed out immediately above.

Those of us concerned with the interrelationships of entocytherids have been aware of the fact that as additional species were added to the two genera, their distinctness became less well defined. With the discovery of Ankylocythere barbouri (linking the Mexican species assigned to the genus Uncinocythere with Ankylocythere toltecae, and it, in turn, through the various “talirotundi” forms of A. heterodonta, to those members of Ankylocythere having a well-developed talon on the clasping apparatus of the male), the advisability of maintaining the two genera does indeed become questionable. Nevertheless, the divergence that has occurred within the two is so great that uniting them does not seem fully justified. Furthermore, the two genera may still be recognized on the basis of the presence or absence of a talon or excrescence on the horizontal ramus of the clasping apparatus of the male.

In reference to the assumed relationships with members of the genus Uncinocythere, it is note-worthy that the presence of only two apical denticles on the clasping apparatus is limited to the three Mexican species [U. bicuspide, U. cuadricuspide (Rioja, 1945:422), and U. dobbinae (Rioja, 1943:560)] and two [U. equicurva (Hoff, 1944) and U. lucifuga Walton and Hobbs, 1959] from the southeastern part of the United States [within the range of the crayfish subgenus Pennides, and the former occurring on Procambarus (Pennides) spiculifer (LeConte, 1956)]. Perhaps it is significant that the peniferum of U. lucifuga is remarkably similar to that of A. barbouri, and, in some individuals of both U. equicurva and U. lucifuga, there are two teeth on the preaxial border of the horizontal ramus of the clasping apparatus that are arranged much as they are in A. barbouri, thus differing from the latter chiefly in lacking an excrescence on the horizontal ramus of the clasping apparatus.

Palaemonetes (Palaemonetes) lindsayi, new species

FIGURES 4–7, 8e

DIAGNOSIS.—Rostrum dentate: art in general reaching extremity of antennal scale. Telson with 4 dorsal spines; distal margin with 4 spines and 2 setae, none of which exceeding distal end of uropod. Ventral ramus of lateral flagellum of antennule with 3 or 4 free articles. Antennal scale 3.5 times longer than wide. Endopodite of first maxilla with 3 spines. First maxilliped with unilobulate gill. Second maxilliped with mesial border of branchial ramus entire. Third maxilliped with 2 podobranchs, proximal one very small. Appendix masculina as long as endopodial ramus of pleopod and bearing 4 apical and 2 (including distal member of row) subapical spines.

DESCRIPTION.—Rostrum gently curved and reaching extremity of antennal scale in 39.3 percent of individuals examined, in others (24.4 percent) projecting beyond scale, and in remaining specimens (36.3 percent) rostrum not quite reaching distal end of scale; dorsal margin armed with 6 or 7 teeth, latter number predominant; ventral margin with 2, more usually 3, or rarely 4, teeth; single dorsal tooth situated posterior to orbit (Figures 4, 5). Antennal and branchiostegal spines quite long and sharp, former implanted submarginally, latter on margin. Hepatic groove extending to anterior border of carapace, slightly above antennal spine.

Pleuron of second abdominal somite rounded both antero- and posteroventrally, its width in females equal to length of tergum of third somite, and in males 0.75 length of latter. Tergal length of sixth somite equal to that of telson not including distal spines (Figure 4).

Telson with 2 pairs of dorsal spines in posterior 0.25 somewhat asymmetrically arranged, but posterior pair situated about midway between anterior pair and posterolateral angle; posterior margin, prolonged in median acute angle, provided with pair of short posterolateral spines, pair of longer more median ones, and pair of plumose setae inserted mesial to long spines (Figure 6a-e).

Eye well developed, cornea and peduncle together pyriform (Figure 6f).

Antennular peduncle with apex of stylocerite reaching midlength of first article. Lateral flagellum of antennule bifurcate at thirteenth to fifteenth article from base; ventral ramus, consisting of 3 or 4 free articles, about 0.33 length of basal undivided portion of flagellum (Figure 6g, h).

Antennal scale 3.5 times longer than wide; lateral border weakly concave, free portion of scale, from base of spine to distal margin, 0.2 total length of scale; length of distal article of antennal peduncle equal to greatest width of scale (Figure 6i, j).

First maxilla (Figure 6l,m) with bifurcate palp; distal margin of lateral lobe lacking setae or spines, that of mesial, or more proximal, lobe armed with 3 spines bent at angle. Gnathal lobules as illustrated.

Second maxilla (Figure 6n) with extremities of scaphognathite rounded, its width almost uniform. Palp with distal half naked. Gnathal lobules as illustrated.

First maxilliped (Figure 7a) with branchial epipodite bearing slight lateral emargination. Second maxilliped (Figure 7b) with branchial epipodite bilobed, one lobe entire, other with digitiform processes. Third maxilliped (Figure 7c) with 2 podobranchs, large distal one with digitiform processes, and proximal one small with irregular margins.

First pair of pereiopods reaching base of distal third of antennal scale. Carpus and merus subequal in length (Figure 7d). Setiferous organs present on ventrodistal part of carpus, ventroproximal region of propodus, and on dactyl of chela (Figure 7e); length of palm equal to that of dactyl; opposable margin of fingers without teeth, single marginal row of setae on both sides of margin in each finger.

FIGURE 4.—Palaemonetes (Palaemonetes) lindsayi: a, lateral view of holotypic male; b, lateral view of ovigerous paratypic female. (Scale in mm.)

Second pair of pereiopods overreaching rostrum by length of distal third of carpus and chela; merus equal in length to chela, and dactyl shorter than palm (Figure 7f,g); opposable margins of fingers without teeth.

Third pair of pereiopods (Figure 7h) with 3 spines on ventral margin of propodus and 1 spine at ventrodistal extremity. Fourth pair of pereiopods with 4 spines on ventral margin of propodus and another ventrodistally (Figure 7i), and, in addition, series of lateral spines on lateral surface. Fifth pair of pereiopods (Figure 7j) with 6 spines on ventral margin of propodus; ventrodistal portion of latter with setiferous organ as depicted (Figure 7l). Ventral border of dactyl of third through fifth pereiopods in females regularly curved, in males with subdistal, almost angular excavation (Figure 7k).

Second pleopod of male (Figures 7n,o, 8e) with appendix masculina as long as endopod and provided with row of spines along almost its entire length; distal extremity with group of 4 apical spines and 2 (including distal member of row) subapical spines.

MEASUREMENTS (mm).—

FIGURE 5.—Palaemonetes (Palaemonetes) lindsayi: variation in rostrum. (Grid in mm.)

FIGURE 6.—Palaemonetes (Palaemonetes) lindsayi: a, telson and uropods of male; b, e, telson of adult females; c, d, telson of adult males; f, dorsal view of antennule and eye; g, ventral view of antennule; h, ventral view of external and accessory flagella of antennule; i, dorsal view of basal portion of antenna; j, ventral view of same; k, mandibles; l, first maxilla; m, details of palp of same; n, second maxilla, (a–e to scale 1; f, g to scale 2; i, j to scale 3; k, l, n to scale 4; scales in mm.)

FIGURE 7.—Palaemonetes (Palaemonetes) lindsayi: a, first maxilliped; b, second maxilliped; c, third maxilliped; d, first pereiopod; e, chela of first pereiopod; f, second pereiopod; g, chela of second pereiopod; h, i, j, third, fourth, and fifth pereiopods; k, distal extremity of dactyl of pereiopods 3–5; l, distal extremity of propodus of fifth pereiopod of male; m, same of female; n, second pleopod of male; o, distal portion of appendix masculina. (a–d, f, h–j to scale 1; e, k–m to scale 2; g to Scale 3; n to Kale 4; scales in mm.)

HABITAT.—Margins of irrigation canals, among the submerged vegetation where the current is more sluggish.

TYPE-LOCALITY.—Springs and canals in the watershed of Laguna de la Media Luna, 4.8 miles (6.6 km) south of Río Verde (on the road to Pedro Montoya) and 2.5 miles (4 km) to the west on a road to the Mina El Refugio, San Luis Potosí, Mexico.

DISPOSITION OF TYPES.—The type-series consists of the holotypic male, USNM 149161, the allotypic female, USNM 149162, and 25 males and 25 females, all deposited in the National Museum of Natural History, Smithsonian Institution; the remaining paratypes are in the collection of Crustacea in the Instituto de Biologia, Universidad Nacional Autónoma de México, and the collection of Crustacea of the Facultad de Ciencias Biológicas, Universidad Nacional Autónoma de Nuevo Léon, Mexico.

DISTRIBUTION.—Known only from the type-locality.

ETYMOLOGY.—This species is dedicated to George E. Lindsay, eminent student of cacti and director of the California Academy of Sciences.

RELATIONSHIPS.—Our knowledge of the genus Palaemonetes in Mexico is so fragmentary, and that of the limits of variations in the four freshwater representatives in the United States so inadequately known, the affinities of the species described here cannot be properly assessed. Overlooking the lack of pigment in P. (P.) cummingi Chace, 1954, all five of the known species belonging to the nominate subgenus are remarkably similar, and few characters have been found that serve to separate them.

TABLE 1.—Diagnostic features of North and Middle American freshwater Palaemonetes

FIGURE 8.—Distal portions of appendices masculinae in postaxial view: a, Palaemonetes (Alaocaris) antrorum; b, Palaemonetes (Palaemonetes) kadiakensis; c, P. (P.) cummingi; d, P. (P.) paludosus; e, P. (P.) lindsayi; f, P. (P.) suttkusi. (Not drawn to same scale.)

Holthuis (1952), in monographing the American Palaemoninae, summarized the ranges of the three known freshwater species and used spination of the carapace, telson, and uropods as the primary characters for distinguishing between the two epigean members. Subsequently, some specimens from the southeastern part of the United States could not, on the basis of those characters, be identified. Fleming (1969), investigating the secondary sexual characters of certain members of the genus, found that a reliable characteristic for distinguishing between P. (P.) paludosus (Gibbes, 1850) and P. (P.) kadiakensis Rathbun, 1902, exists in the number and distribution of the setae of the apical region of the appendix masculina.

The characteristics presented in Table 1 include most of those that we have found to be useful in assessing probable relationships and in distinguishing between the six known freshwater species of the genus occurring in North America and Middle America. The overlap in most of the other characters that we have investigated is such that one must conclude that, excluding P. (Alaocaris) antrorum, Benedict, 1896, the remaining species comprise a closely allied group. Of the previously described species, adequate series are available of only P. (A.) antrorum, P. (P.) kadiakensis, and P. (P.) paludosus. There are only 4 specimens of P. (P.) cummingi known to us, and only 13 specimens of P. (P.) suttkusi Smalley, 1964, have been reported.

Utilizing the limited data available, and perhaps emphasizing the resemblance existing between the appendices masculinae (Figure 8a-f), we believe that the closest relatives of P. (P.) lindsayi are P.(P.) suttkusi (Coahuila Province, Mexico) and P. (P.) paludosus (New Jersey to Florida).

The key on page 16 will assist in recognizing the species mentioned above.

Discussion

As has been pointed out in the sections devoted to relationships of the three crustaceans, the affinities of the crayfish, Procambarus roberti, seem clearly to be with species occurring principally in the southeastern part of the United States, and the discovery of the geographically disjunct member of the stream-dwelling subgenus Pennides in a stream within the Sierra Madre Oriental, so far south in Mexico, came as a great surprise.

Certain resemblances of P. roberti to members of the subgenus Villalobosus (a group of crayfishes confined to a relatively small area north of the Cordillera Volcánica Transversal in the states of Hidalgo, Puebla, and Veracruz) were noted above. Both the morphological similarities and geographic position of P. roberti suggest that it was derived from the ancestral stock that was the forerunner of Villalobosus. If Hobbs’ views concerning the invasion of Mexico by crayfish stocks from the north prove to be admissible (Hobbs, 1971:12, 13; see summary table and Figure 6b), then P. roberti represents a relict of one of the three stocks (“5B”) migrating southward into Mexico during the Pliocene.

Key to the North and Middle American Freshwater Species of the Genus Palaemonetes

With the assumed passive migration (Hobbs, 1971:10) of the ostracod on crayfish hosts, and if the suggested relationships of the hosts, as pointed out above, are valid, one might assume that the ostracods occurring on P. roberti would show affinities with those ostracods infesting members of the subgenus Villalobosus, and this is precisely what we believe has been found. Ankylocythere barbouri indeed is markedly similar to Uncinocythere bicuspide (Rioja, 1943), which infests six crayfishes belonging to the subgenus Villalobosus. Its importance in linking the previously recognized genus Uncinocythere with Ankylocythere has been discussed in the paragraphs devoted to its relationships.

In discussing the origin of the Mexican entocytherid fauna, Hobbs (1971:15-17) stated that the Uncinocythere stock, “generally considered to be the most primitive of the subfamily [Entocytherinae], apparently was brought into Mexico during the Pliocene by one or more of the three stocks of crayfishes (one of which is rather primitive [P. roberti is believed to be a descendant of that stock]) that moved southward across the Northern Gulf Slope [1971:10-11] to populate the interjacent area.” He further indicated that Ankylocythere toltecae, which is restricted to a small area in southern Tamaulipas, eastern San Luis Potosí, and extreme northern Hidalgo … is associated with only two hosts, P. toltecae and P. villalobosi … remnants of the Pliocene crayfish migration passing through the Northern Gulf Slope southward. In fact, these two represent the only suspected traces of the Pliocene crayfish stock that have remained in that area [P. roberti is the third]. Why they should harbor a member of the genus Ankylocythere while their close relatives to the south are infested by members of the genus Uncinocythere poses a problem in itself.

After exploring possible explanations, he “favored” the hypothesis, “that A. toltecae is viewed as a relict of the pioneering [pre-Pliocene] Ankylocythere stock which, before the extinction of its original hosts, managed to gain access to certain members of the Pliocene crayfish invaders as alternative hosts.”

With the discovery of A. barbouri in the Northern Gulf Slope, linking A. toltecae to U. bicuspide, one could hardly overlook the possibility of an in-dependent acquisition of the excrescence on the clasping apparatus by their immediate ancestors from the Pliocene Uncinocythere stock that gave rise to the Mexican members of Uncinocythere. While this would suggest at least a diphyletic origin of Ankylocythere from the more primitive Uncinocythere, it would permit a strong parallel with the assumed migrations of the host stocks, and, in addition, it would provide an explanation for the marked similarities betwen A. barbouri and the two members of Uncinocythere (U. equicurva and U. lucifuga) occurring in the southeastern part of the United States. Even though such an explanation is in keeping with our present knowledge, until more conclusive evidence for the di- or polyphyletic origin of Ankylocythere becomes available, recognition of the two generic groups does not seem in-appropriate.

As pointed out above, there are so few data on the range of the genus Palaemonetes in Mexico, and one of the American species is so poorly known, there is little to suggest the source of the stock from which this new species was derived. If our tentative conclusion—that Palaemonetes (P.) lindsayi is most closely allied to P. (P.) suttkusi and P. (P.) paludosus—proves to be tenable, then there exists a similar pattern of relationships (Mexico and the southeastern part of the United States) parallel to that postulated for the crayfish and entocytherid frequenting the waters of La Media Luna.

It seems highly probable to us that the crayfish and its ostracod commensal (also possibly the shrimp), in contrast to most of the fish fauna (see Miller, 1956:15), have affinities with the nearctic faunas rather than with tropical ones.

Literature Cited

Benedict, J. E.

1896. Preliminary Descriptions of a New Genus and Three Species of Crustaceans from an Artesian Well at San Marcos, Texas. Proceedings of the United States National Museum, 18(1087):615–617.

Chace, Fenner A., Jr.

1954. Two New Subterranean Shrimps (Decapoda: Caridea) from Florida and the West Indies, with a Revised Key to the American Species. Journal of the Washington Academy of Sciences, 44(10):318–324, 2 figures.

Fleming, Laurence E.

1969. Use of Male External Genitalic Details as Taxonomic Characters in Some Species of Palaemonetes (Decapoda, Palaemonidae). Proceedings of the Biological Society of Washington, 82(34):443–452, 14 figures.

Gibbes, L. R.

1850. On the Carcinological Collections of the Cabinets of Natural History in the United States. With an Enumeration of the Species Contained Therein, and Descriptions of New Species. Proceedings of the American Association for the Advancement of Science, 3:165–201.

Hobbs, Horton H., Jr.

1951. A New Crayfish of the Genus Procambarus from Louisiana with a Key to the Species of the Spiculifer Group. Journal of the Washington Academy of Sciences, 41(8):272–276, 11 figures.

1969. Two New Species of the Crayfish Genus Procambarus (Decapoda, Astacidae) with Keys to the Members of the Spiculifer Group. Proceedings of the Biological Society of Washington, 83(24):329–348, 38 figures.

1971. The Entocytherid Ostracods of Mexico and Cuba. Smithsonian Contributions to Zoology, 81: 55 pages, 31 figures.

1972. The Subgenera of the Crayfish Genus Procambarus (Decapoda, Astacidae). Smithsonian Contributions to Zoology, 117: 22 pages, 20 figures.

Hoff, C. Clayton

1944. New American Species of the Ostracod Genus Entocythere. American Midland Naturalist, 32(2):327–357, 33 figures.

Holthuis, Lipke B.

1952. A General Revision of the Palaemonidae (Crustacea Decapoda Natantia) of the Americas, II: The Subfamily Palaemoninae. Allan Hancock Foundation Publications, Occasional Paper, 12: 396 pages, 55 plates.

LeConte, John

1856. Descriptions of New Species of Astacus from Georgia. Proceedings of the Academy of Natural Sciences of Philadelphia, 7:400–402.

Miller, Robert Rush

1956. A New Genus and Species of Cyprinodontid Fish from San Luis Potosí, Mexico, with Remarks on the Subfamily Cyprinodontinae. Occasional Papers of the Museum of Zoology, University of Michigan, 581: 17 pages, 2 plates, 2 figures.

Ortmann, A. E.

1905. The Mutual Affinities of the Species of the Genus Cambarus, and Their Dispersal over the United States. Proceedings of the American Philosophical Society, 41(171):267–400, 8 figures.

Penn, George Henry, Jr.

1953. A New Crawfish of the Genus Procambarus from Louisiana and Arkansas (Decapoda: Astacidae). Journal of the Washington Academy of Sciences, 43(5):163–165, 12 figures.

1963. A New Crawfish from the Hatchie River in Mississippi and Tennessee (Decapoda, Astacidae). Proceedings of the Biological Society of Washington, 76(15):121–126, 10 figures.

Rathbun, Mary J.

1902. Descriptions of New Decapod Crustaceans from the West Coast of North America. Proceedings of the United States National Museum, 24(1272):885–905.

Rioja, Enrique

1943. Estudios Carcinológicos, XIV: Nuevos Datos acerca de los Entocythere (Crust. Ostrácodos) de México. Anales del Instituto de Biologia, Universidad National Autónoma de México, 14(2):553–566, 24 figures.

1945. Estudios Carcinológicos, XVIII: Observaciones acerca de las Variaciones de la Pieza Copuladora en Entocythere dobbini, Rioja (Crust. Ostrácodos). Anales del Instituto de Biologia, Universidad National Autónoma de Mexico, 16(2):419–423, 4 figures.

Smalley, Alfred E.

1964. A New Palaemonetes from Mexico (Decapoda, Palaemonidae). Crustaceana, 6(3):229–232, 1 figure.

Villalobos, Alejandro

1955. Cambarinos de la Fauna Mexicana. xvi + 290 pages, 62 plates. Tesis, Facultad de Ciencias, Universidad Nacional Autónoma de México.

Walton, Margaret, and Horton H. Hobbs, Jr.

1959. Two New Eyeless Ostracods of the Genus Entocythere from Florida. Quarterly Journal of the Florida Academy of Sciences, 22(2):114–120, 20 figures.

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