9 Octote 2001 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 114(3):640-648. 2001. A new species of Stebbing (Crustacea: : ) from the Pacific coast of Mexico ^

%^ Ma. del Carmen Espinosa-Perez and Michel E. Hendrickx Unidad Academica Mazatlan, ICML, UNAM, P.O. Box 811, Mazadan, Sinaloa 82000, Mexico.

Abstract.—Exosphaeroma bruscai is described from the Pacific coast of Mexico. Exosphaeroma bruscai is most closely related to E. diminuta Menzies & Frankenberg, 1966 from the western Atlantic, from which it differs in having much longer antenna, an acute rostrum, a triangular first pleopod endopod, a transverse suture on exopod of pleopods 3-5, and a considerably longer and more slender appendix masculina. Specimens examined here define the geo­ graphic distribution of E. bruscai from the central Gulf of California to Los Arcos, in the southern part of Banderas Bay, Jalisco. Previously published records of an unidentified Exosphaeroma from the eastern tropical Pacific in­ dicate that E. bruscai occurs from sandy beaches of the upper Gulf of Cali­ fornia to Colombia.

Sphaeromatidae is the most specious species for similar habitats in Costa Rica family of marine isopods. According to a and Colombia. This identification, however, recent survey it contains 633 species (Ken- was considered doubtful by Brusca & Iver­ sley & Schotte 2000) and they are often son (1985:26-28) who thought that Pacific very abundant in intertidal and shallow wa­ records of Dexter (1974, 1979) belong to ter habitats. Their is one of the an undescribed species, probably extending most confused among isopods, in great part from the upper Gulf of California, Mexico, due to marked sexual dimorphism in some to Parque Nacional Santa Rosa, Costa Rica. genera (Schultz 1969, Brusca 1980, Ken- Brusca & Iverson (1985:26-28) provided sley & Schotte 1989) and to the difficulty some diagnostic characters of this undes­ in establishing generic relationships within cribed Exosphaeroma, illustrated parts of the family (see Bruce 1995). The family has an adult male, but did not give it a new been formally divided into five subfamilies name. by Iverson (1982), who based his study on Since Brusca and Iverson's 1985 note on previous works by Hurley & Jansen (1977) this , another report of an Exosphae­ and Bowman (1981). More recently, genera roma sp. was published by Rios & Ramos of Sphaeromatidae have been reviewed by (1990) from specimens collected in Malaga Harrison & Ellis (1991) who presented an Bay, Colombia. These authors refer to the identification key to genera. data presented by Brusca & Iverson (1985). The genus Exosphaeroma is known from No further reports on Exosphaeroma from the Pacific coast of Mexico, but no identi­ the Pacific coast of America have been pub­ fied species has been recorded. The first lished. Recent collecting along the Pacific published record of Exosphaeroma for the coast of Mexico, including sampling on area is by Dexter (1972) who recorded E. sandy beaches, led to the discovery of an diminuta Menzies & Frankenberg, 1966, a undescribed species similar to those of west Atlantic sphaeromatid, from sandy Brusca & Iverson (1985) in several locali­ beaches of the west coast of Panama. Dex­ ties. The purpose of the present paper is to ter (1974, 1979) later reported the same formalize the description of this apparently VOLUME 114, NUMBER 3 641 abundant species, the first of the genus Ex- 2), not ventrally directed, without suture, osphaeroma reported for the Pacific coast not narrowed. Pleon with 3 incompletely of America. fused pleonites. Pleotelson smooth, wider Abbreviations used in this paper are: St., than long, regularly curving towards pos­ sampling station; TL, total length; NS, un- terior margin in lateral view (Fig. IB, D); sexed specimen; coll., collector; EMU, Un- wider anteriorly, posteriorly rounded in dor­ idad Academica Mazatlan UNAM Inverte­ sal view. Epistome scarcely visible in dorsal brates Reference Collection. view; elongate in ventral view (Fig. IE), about twice as long as wide in its middle Sphaeromatidae H. Milne-Edwards, 1840 part, apex truncate, posterior arms shorter Exosphaeroma Stebbing, 1900 than anterior portion. Antennular peduncle Exosphaeroma bruscai, new species with 3 articles; flagellum with 8—9 articles. Figs. 1-5 Antennal peduncle with 4 articles; flagel­ lum with 11-12 articles, twice as long as Exosphaeroma diminutum.—Dexter, 1972: antennular flagellum (Fig. IE). Mandibular 425; 1974:54; 1979:547 (Pacific records palp of 3 articles; 2 distal articles with 9 only). and 14 spines. Left mandible with incisor Exosphaeroma sp.—Brusca & Iverson, 4-dentate and lacinia mobilis (3-dentate); 1985:26-28, fig. lOb-d.—Rios & Ramos, setal row of 4 serrate setae; molar process 1990:86-87, fig. 2. serrate. Right mandible similar in shape, Type material.—Holotype, 1 male (TL 4.6 with a 4-dentate incisor; setal row of 4 ser­ mm), Los Arcos (20°32.5'N, 105°18.4'W), rate setae; molar process with dentate mar­ Jalisco, Mexico, 12 Apr 1996 (EMU-4745). gin and a seemingly rugose surface (Fig. Paratypes, 3 females (TL 1.9-2.8 mm), Los 3A, B). Apex of the lateral lobe of maxil- Arcos (20°32.5'N, 105°18.4'W), Jalisco, lula (Fig. 3C) with 6 serrate setae, and 3 Mexico, 12 Apr 1996 (EMU-5357). slender non-plumose, non-serrate setae; me­ Additional material.—El Tesoro (24° sial lobe with 4 plumose setae, and a short 18.0'N, 110°19.0'W), La Paz, Southern non-plumose seta. Maxilla (Fig. 3D) lateral Baja Cahfornia, Mexico, 17 Jul 1996, 2 lobe with 6 serrate setae, middle with 7, and ovigerous females (TL 1.6-2.6 mm) and 1 mesial lobe with 7 plumose setae and a unsexed, unmeasured specimen (EMU- much longer, slender, mesial plumose setae. 4743). Piedras Pintas (27°56.5'N, 111° Maxilliped palp (Fig. 3E) with 4 articles; 05.5'W), Sonora, Mexico, 24 Mar 1997, 1 11-10-11-8 setae on articles 1-4, respec­ female (TL 4.7 mm) (EMU-4742). Piedras tively; endite with 1 retinaculum, 9 plumose Pintas (27°56.5'N, 111°05.5'W), Sonora, setae, 4 stout non-plumose setae and about Mexico, 24 Mar 1997, 2 females (TL 2.9- 7 setules. 3.4 mm) and 1 ovigerous female (TL 2.4 All pereopods with setules, simple mm) (EMU-4744). Bacochibampo Bay spines, composed spines (stout spines with (27°54.3'N, 110°57.6'W), Guaymas, Sono­ basal part tipped with a slender seta), and ra, Mexico, 26 Mar 1997, 1 ovigerous fe­ diminutive scales on margins. Pereopod 1 male (TL 2.4 mm) collected by diving (Fig. 4A) merus slightly shorter than half (EMU-5376). ischium length; ischium with 4 setae at su­ Description of male.—Body ovate (Fig. perior distal angle; merus with 3 setae at lA, C), about twice as long as wide; dorsal superior distal angle; carpus triangular, surface smooth. Head wide, rostrum short, short, slightly longer than half merus acute. Length of holotype 4.6 mm. Pereon- length; propodus shorter than ischium; dac- ite 3 longest, pereonites 1-2 and 4-5 sub- tylus about half propodus length, with 1 equal in length; pereonite 7 more than half subterminal seta on the lower margin; com­ as long as pereonite 6. Coxae smooth (Fig. posed spines, scales and serrate scales pre- 642 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Fig. 1. Exosphaeroma bruscai, new species. A, Holotype, male, dorsal view (EMU-4745); B, pleotelson, male, lateral view; C, Paratype, female, dorsal view (EMU-5337); D, pleotelson, female, lateral view; E, ceph- alon, male, ventral view; F, uropods, dorsal view, detail; G, penes, male. VOLUME 114, NUMBER 3 643

Fig. 2. Exosphaeroma bruscai, new species, male holotype (EMU-4745). Schematic drawing of body in lateral view; appendages not ilustrated. sent on articles as illustrated. Pereopods 2- dopod of pleopod 2 by about half length of 3 similar, 3rd slightly longer than 2nd. Pe- the latter. Pleopod 3 as illustrated. Exopod reopod 3 (Fig. 4B) merus slightly longer of pleopods 3-5 with complete transverse than half ischium length; ischium with 5 suture. Pleopod 4 (Fig. 5D) endopod with spines near superior distal angle and 1 distinct thickened ridges, 3 short plumose shorter proximal spine; merus with 6 spines marginal setae on ventral margin of exopod at superior distal angle; carpus subcylindri- and 1 on endopod; a row of short non-plu­ cal, similar in length to merus; propodus mose setae on the inner margin of exopod. shorter than ischium; dactylus about half Pleopod 5 (Fig. 5E) endopod with distinct length of propodus, with 1 subterminal thickened ridges, a row of short, non-plu­ spine on the lower margin; composed mose setae on inner margin of exopod and spines, spines, scales and serrate scales pre­ 6 similar setae near ventral margin of en­ sent on articles as illustrated. Pereopod 7 dopod; exopod with a deep cleft along inner (Fig. 4C) longer and more slender than pe­ margin, and 5 small lobes with scales close reopods 1—3; merus with 4 spines at supe­ to inner distal and ventral margins. rior distal angle; carpus distal margin with Uropod exopods of similar length, en­ 2 inferior and a row of 5 superior serrated dopod slightly longer and acute, exopod spines; propodus with 1 bifid spine and 1 with rounded tip. subterminal serrate seta at superior angle; Female.—Body ovate, about twice as composed spines, spines and scales present long as wide. Pleotelson slightly more in­ on joints as illustrated. Pereopods 5-6 sim­ flated than in male, with a weak depression ilar in shape and spination to pereopod 7; near posterior margin. All characters, in­ these pereopods slightly increasing in size cluding all pereopods, very similar to male. from 5th to 7th. Etymology.—This species is named for Penes not fused, about twice as long as Richard C. Brusca, from the BIOSPHERE- basal width (Fig. IG). 2 Center, Tucson, Arizona, in recognition of Pleopods 1-3 (Fig. 5A-C) endopod and his contibution to knowledge of the Isopo- exopod with long, plumose marginal setae da, and for his support of our work. on pleopods as follows (endopod and exo­ Habitat.—In the eastern Pacific, previous pod): pleopod 1,16 and 26; pleopod 2, 18 records of Exosphaeroma are usually from and 27; pleopod 3, 13 and 30; protopod sandy beaches. On Panamanian beaches, with 3 coupling spines. Distal margin of the species was collected in substrate com­ pleopod 1 exopod slightly curved; endopod posed of quartz sand, fine sand and calcar­ triangular Appendix masculina of pleopod eous shell fragments (Dexter 1972). Rios & 2 elongate, slender, distally minutely serrate Ramos (1990) recorded specimens from and curving, tip rounded, overreaching en­ sandy beaches of Colombia. Exosphaeroma 644 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Fig. 3. Exosphaeroma bruscai, new species, male holotype (EMU-4745). A, left mandible; B, right mandible; C, right maxilulla; D, right maxilla; E, right maxilliped. VOLUME 114, NUMBER 3 645

Fig. 4. Exosphaeroma bruscai, new species, male holotype (EMU-4745). A, right pereopod 1; B, right pereopod 3; C, right pereopod 7. 646 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Fig. 5. Exosphaeroma bruscai, new species, male holotype (EMU-4745). A, right pleopod 1; B, right pleopod 2; C, right pleopod 3; D, right pleopod 4; E, right pleopod 5 (ed = endopod; ex = exopod). VOLUME 114, NUMBER 3 647 has also been registered in gravels, off man­ fused. The illustration of the dorsal habitus grove lagoons in Costa Rica (Brusca & provided by Brusca & Iverson (1985: fig. Iverson 1985). In the Gulf of California, 10, B) differs somewhat from our speci­ Mexico, Exosphaeroma has been taken un­ mens; the Costa Rica specimens have an der shell fragments on sandy stretches of anteriorly inflated pleon, a character not so tidal flats (Brusca & Iverson 1985). Records clearly marked in our specimens. This may for E. bruscai are from algae on rocky be due to overshading of the original illus­ beaches from intertidal zone to at least 3 m; tration, as demonstrated by the lateral view environmental data available at the time of of the same pleon (Brusca & Iverson, 1985: sampling indicate epibenthic temperature fig. 10 D) provided by these authors, which range from 20.3 to 28.0°C. is much more similar to our illustration (see Although it seems reasonable to assume Fig. 1). Comparison of original illustrations that all specimens of Exosphaeroma previ­ of E. diminuta by Menzies & Frankenberg ously reported from the region belong to E. (1966) with the new species show the fol­ bruscai, the habitat of specimens described lowing variations: antenna and antennula here differs from the typical sandy beach are similar in size in E. diminuta, while the habitat reported previously by Dexter antenna of E. bruscai is almost twice as (1974, 1979) and Brusca & Iverson (1985). long as the antennula; the rostrum is round­ Furthermore, three species of Exosphaero­ ed in E. diminuta, acute in E. bruscai; en- ma from the Caribbean are known from dopod of first pleopod is triangular in E. sand {E. diminuta) or from algae on rocks bruscai, narrowly oval in E. diminuta; a {E. alba Menzies & Glynn, 1968 and E. transverse suture is present on exopod of productatelson Menzies & Glynn, 1968), pereopods 3—5 in E. bruscai, present only on pereopod 4 in E. diminuta; appendix but none has been reported from both hab­ masculina slender, much longer than pleo­ itats (Kensley & Schotte 1989). Although pod 2 endopod in E. bruscai, stouter, just we believe that previous reports of Exos­ reaching apex of the endopod in E. dimi­ phaeroma from Panama, Costa Rica and nuta; distal 2 articles of maxilliped palp Colombia correspond to E. bruscai, a com­ slender in E. diminuta. According to Men­ parison of specimens from these localities zies & Frankenberg (1966: fig. 21 B), clyp- to type specimens of E. bruscai is desirable. eus of E. diminuta is almost rectangular but Distribution.—The species is known it is figured by Kensley & Schotte (1989: with certainty from Sonora (27°56.5'N, fig. 100 H) as being widest in middle 11]°05.5'W) to Los Arcos (Banderas Bay), length, as in E. bruscai. Jalisco, on the east coast of the Gulf of Cal­ ifornia, and from La Paz, South Baja Cali­ Exosphaeroma bruscai also differs from fornia. It is also known from the west coast other American species of Exosphaeroma of Costa Rica to Colombia. reported by Kensley & Schotte (1989). Ex­ Remarks.—The type species of Exos­ osphaeroma alba has a notched, and E. yu- phaeroma, gigas Leach, 1818, catanum (Richardson, 1901) a trilobate, was recently redescribed (Brandt & Wagele margin of the posterior pleotelson; the pleo- 1989). Exosphaeroma bruscai expresses the telson of E. antillense Richardson, 1912 typical generic characters considered by bears two rounded submedial tubercles; E. Brandt & Wagele (1989), in particular the productatelson, features broad lateral patch­ ridges or folds of pleopods 4 and 5, and the es of pigment on pleotelson, not observed two posteriorly directed submedian flat on any specimen of E. bruscai. lobes on pleonite 1 (see Bruce 1994). Ex­ osphaeroma bruscai is very similar to E. Acknowledgments diminuta which occurs in the western At­ The authors thank scientists and students lantic and with which is was originally con­ who provided assistance during field work. 648 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Graciano Valenzuela drew figure 1. Mer­ es.—Estuarine and Coastal Marine Science 9: cedes Cordero did the final editing of the 543-558. Harrison, K., & J. P. ElUs. 1991. The genera of the manuscript. German Ramirez provided sup­ Sphaeromatidae (Crustacea: Isopoda): a key and port with computing software. Part of this distribution list.—Invertebrate Taxonomy 5: study was supported by CONABIO (Com- 915-952. ision Nacional para el Uso y Conocimiento Hurley, D. E., & K. P. Jansen. 1977. The marine fauna of New Zealand: family Sphaeromatidae (Crus­ de la Biodiversidad), Mexico, project H170. tacea: Isopoda: Flabellifera).—New Zealand Oceanographic Institute Memoir 63:1-80. Literature Cited Iverson, E. W. 1982. Revision of the isopod family Sphaeromatidae (Crustacea: Isopoda: Flabelli­ fera) I. Subfamily names with diagnoses and Bowman, T. E. 1981. milleri and T. key.—Journal of Biology 2:248- smithi, new sphaeromatid isopod 254. from hot springs in Chihuahua, Mexico, with a Kensley, B., & M. Schotte. 1989. Guide to the marine review of the genus.—Journal of Crustacean Bi­ isopod crustaceans of the Caribbean. Smithson­ ology 1:105-122. ian Institution Press, Washington, D.C., 308 pp. Brandt, A., & J. W. Wagele. 1989. Redescriptions of , & . 2000. World list of marine and Cymodocella tubicauda Pfeffer, 1887 and Ex- freshwater Crustacea Isopoda. (URL-.http:/ / osphaeroma gigas (Leach, 1818) (Crustacea, Is- nmnhwww.si.edu/gopher-menus/WorldListof opoda, Sphaeromatidae).—Antarctic Science 1: MarineandFreshwaterCrustaceaIsopoda.html) 205-214. Leach, W. E. 1818. Cymothoadees. in F Cuvier ed., Bruce, N. L. 1994. Four new genera of marine isopod Dictionnaire des Sciences Naturelles 12:338- crustaceans (Sphaeromatidae) from eastern and 354. southern Australia.—Memoirs of the Museum Menzies, R. J., & D. Frankenberg. 1966. Handbook on of Victoria 54:399-438. the common marine isopod Crustacea of Geor­ . 1995. The taxonomy and phylogeny of tube- gia. University of Georgia Press, Athens, 93 pp. tailed sphaeromatid isopods (Crustacea) with , & P. W. Glynn. 1968. The common marine descriptions of new species and a new genus isopod Crustacea of Puerto Rico.—Studies on from southern Austraha.—Ophelia 43:127-180. the Fauna of Curasao and other Caribbean Is­ Brusca, R. C. 1980. Common intertidal invertebrates lands, 27:1-133. of the Gulf of California. The University of Ar­ Richardson, H. 1901. Key to the isopods of the Atlan­ tic coast of North America, with descriptions of izona Press, Tucson, 513 pp. new and little known species.—Proceedings of , & E. W. Iverson. 1985. A guide to the marine the United States National Museum 23:493- isopod Crustacea of Pacific Costa Rica.—Revis- 579. ta de Biologia Tropical 33:1-77. . 1912. Marine and terrestrial isopods from Ja­ Dexter, D. M. 1972. Comparision of the community maica.—Proceedings of the United States Na­ structures in a Pacific and Atlantic Panamanian tional Museum 42:187-194. sandy beach.—Bulletin of Marine Science 22: Rios, R., & G. E. Ramos. 1990. Los isopodos (Crus­ 449-485. tacea: Isopoda) de Bahia Malaga, Colombia.— . 1974. Sandy-beach fauna of the Pacific and Revista de Ciencias, Universidad del Valle 2: Atlantic coast of Costa Rica and Colombia.— 83-96. Revista de Biologia Tropical 22:51-66. Schultz, G. A. 1969. How to know the marine isopod . 1979. Community structure and seasonal var­ crustaceans. W.M.C. Brown Company Publish­ iation in intertidal Panamanian sandy beach­ ers, Dubuque, Iowa, 359 pp.

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