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A New Species Of Cassidinidea Hansen (Isopoda : Sphaeromatidae) And First Record Of The Genus From The Eastern Tropical Pacific
| Content Provider | Semantic Scholar |
|---|---|
| Author | Hendrickx, Michel E. |
| Copyright Year | 1998 |
| Abstract | —Cassidinidea mexicana, a new species, is described from an abundant material from the southeastern Gulf of California, on the west coast of Mexico. The species is closely related to the type species of the genus, C. ovalis (Say) with which it shares a very similar appendix masculina, and an almost similar arrangement of trifid serrated spines on the distal margin of the carpus of pereopod 7. The absence of dorsal nodules on pereonites (very weak, almost wanting, in ovalis) and the presence of a single, median elevation on the pleotelson are other similarities between the two species. It differs from this Atlantic species, however, by the presence of a pair of weak ridges almost parallel to the lateral margin of the pleotelson, the presence of another pair of ridges, inverted "v"-shaped, running from the anterior part of the median elevation of the pleotelson towards its posterior margin, and the absence of a clear indentation on the distal margin of the exopod of pleopod 1. The new species is the first record of the genus Cassinidinea in the east Pacific region. The subfamily Cassidininae Hansen was recently reviewed by Bruce (1994). Species of this subfamily of Sphaeromatidae Latreille are small and usually associated with shallow water, estuarine or coastal lagoonal habitats. Although he indicates that " . . . the resolution of the status of the Cassidininae must wait until further data are available on the [two other subfamilies] Sphaeromatinae and Dynameninae" Bruce (1994:1083) implicitly accepted the validity of the Cassidininae by providing synonymy and diagnosis. Bruce (1994) further divided the genera of Cassidininae into three groups: the "Cassidina" group, the "Leptosphaeroma" group, and the "'Cassidinidea" group. The material on which this study is based clearly belongs to the Cassinididea group (containing only two genera) for the following reasons: the lateral margins of the cephalon are expanded (not expanded in the Leptosphaeroma group) and the pleon has only one segment (three segments in the Cassidina group). It is distinct from Syncassidina Baker, the second genus belonging to the ''Cassidinidea" group, in having non-flattened first and second antennule peduncle articles. Its affinity with the genus Cassidinidea Hansen is confirmed by the presence of the very long and acute appendix masculina set on a proximal directed expansion of the endopod of male pleopod 2, the absence of a rostral point, pleon without sutures and a relatively wide epistome. Dorsal nodules are apparently very weak or wanting (as in Naesa ovalis Say, 1818, the type species of Cassidinidea), except on the pleotelson. The exact composition of the genus Cassidinidea Hansen is still to be confirmed. According to Bruce (1994), several Atlantic species are probably synonyms of previously described species [e.g., C. ovalis (Say, 1818)]. All together, there seems to be 10 valid species, none from the east Pacific. The presence of the herein described new species along the coast of western Mexico, represents the first record of the genus Cassidinidea for the west coast of America. 296 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Abbreviations used in this paper are: TL, total length; coll., collector; EMU, Estacion Mazatlan UNAM Invertebrates Reference Collection; USNM, United States National Museum, Smithsonian Institution, Washington D.C., U.S.A.; QM, Queensland Museum, Brisbane, Australia. Family Sphaeromatidae Latreille, 1825 Genus Cassidinidea Hansen, 1905 Cassidinidea mexicana, new species Figs. 1-4 Type material.—Holotype, 1 male (TL 3.0 mm), Estero Sirena (23°09.03'N, 106°19.00'W), Mazatlan, Sinaloa, Mexico, 24 Apr 1997 (EMU-4072). Paratype, 1 female (TL 3.7 mm), same locality, 24 Apr 1997 (EMU-4073). Paratypes, 2 males (TL 2.5 and 2.8 mm) and 2 ovigerous females (TL 4.0 and 4.2 mm), same locality, 24 Apr 1997 (USNM 285513). Paratypes, Estero el Infiemillo, Mazatlan, Sinaloa, Mexico, 14 Mar 1996, 1 male (TL 3.2 mm) and 1 female (TL 2.9 mm) (QM W22716). Paratypes, 3 males (TL 2.7-3.1 mm) and 8 females (TL 1.6-3.7 mm), same locality, 24 Apr 1997 (EMU-4074) (All specimens, coll. J. Salgado-Barragan and M. C. Espinosa-Perez). Additional material.—Estero el Infiemillo, Mazatlan, Sinaloa, Mexico, 06 Sep 1995, 1 male (TL 2.8 mm), 1 female (TL 3.4 mm), and 1 ovigerous female (TL 3.1 mm) (EMU-4432) (coll. J. Salgado-Barragan and M. C. Espinosa-Perez). Same locality, 14 Mar 1996, 3 males (TL 2.7-3.1 mm), and 3 females (TL 2.8-3.5 mm) (EMU-4433) (coll. J. Salgado-Barragan and M. C. Espinosa-Perez). Estero Caiman (23°09.20'N, 106°19.93'W) 1 female (TL 3.5 mm) (EMU-4434) (coll. J. Salgado-Barragan). Estero el Verde (23°25'N, 106°34'W), Sinaloa, Mexico, 10 Feb 1979, 2 ovigerous females (TL 4.0-4.3 mm) (coll. M. E. Hendrickx) (EMU-4435). Estero Barron (23°08.87'N, 106°18.78'W), 24 Feb 1994, 1 male (TL 3.0 mm) (EMU4436) (coll. J. Salgado-Barragan). Estero Sirena (23°09.03'N, 106°19.00'W), Mazatlan, Sinaloa, Mexico, 24 Apr 1997, 1 male (TL 2.5 mm), 6 females (TL 1,4-2.7 mm), and 2 ovigerous females (TL 3.4 mm) (EMU-4630). Description of male.—Body ovate, about 1.8 times as long as wide; pereonites 1-7 without sub-median nodules (Fig. lA) . Pleotelson with a median elevation and a pair of lateral ridges; another pair of inverted 'V-shaped ridges running from the anterior part of the median elevation towards posterior margin of the pleotelson. Epistome (Fig. 3F) anterior margin almost straight, reduced, less than half the length of cephalon in dorsal view. Epistome in ventral view subrectangular, slightly longer than broad, lateral and posterior sides strongly concave. Cephalon without rostral point. Antennule peduncle (Fig. 2A) with 3 articles; flagellum with 7 articles, long, extending slightly beyond half of pereonite 2. Antenna peduncle (Fig. 2B) with 5 articles; flagellum with 8 articles, slightly longer than antennular flagellum. Mandible palp (Fig. 3B) articles 1 and 2 with 5 serrated spines each. Left mandible with incisor tooth 3-dentated (an inconspicuous fourth) and lacinia mobilis (3dentated); setal row of 3 serrated setae; molar process with a straight serrated margin. Right mandible similar in shape, with only one 3-dentated (an inconspicuous fourth) incisor tooth; setal row made of 3 serrated setae and one bifid serrated setae; molar process as in left mandible. Apex of the lateral lobe of maxillula (Fig. 3D) with 8 non-plumose, non-serrated spines, and 2 serrated spines; medial lobe with 4 plumose spines. Maxilla (Fig. 3C) lateral lobe with 4 serrated spines, middle with 4, and medial lobe with 5 plumose spines (the inner one mounted on a short lobular process) and two slender non-plumose spines. Maxilliped palp (Fig. 3E) with only 4 distinguishable articles; about 7-8-6-7 setae on articles 1—4, respectively. All pereopods with setules on margins. Pereopod 1 (Fig. 2C) merus about half as VOLUME 111, NUMBER 2 297 |
| Starting Page | 295 |
| Ending Page | 302 |
| Page Count | 8 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://research.nhm.org/pdfs/2274/2274.pdf |
| Volume Number | 111 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
