Elasmopus spinimanus Walker, 1904

Chandani Appadoo, 2003, The Genus Elasmopus (Crustacea: Amphipoda: Melitidae) from Mauritius (Indian Ocean) with Description of Five New Species, Records of the Australian Museum 55, pp. 61-84 : 78

Elasmopus spinimanus Walker

Fig. 12

Elasmopus spinimanus Walker, 1904: 277 , pl. 5, fig. 36.– Pirlot,1936: 313.– Schellenberg, 1938: 55.– Myers, 1985: 109, fig. 87.

Material examined. 13, from mixture of Amansia glomerata , Jania adherens and Sargassum densifolium, Souillac (20°31'S 57°30.7'E), 10 Feb. 2000.

Description. Male, 3.8 mm. Head, with subocular notch; eyes large, subround with circular disc of clear ommatidia enclosing a dark core. Antenna 1, article 2 subequal to 1; article 3, 0.5× article 1; accessory flagellum 3-articulate, article 3 vestigial; primary flagellum 20-articulate. Antenna 2, article 5, 0.8× article 4; flagellum 7-articulate, the terminal article rudimentary. Mandible, palp article 2 with 1 strong distal seta and 2 short medial setae; article 3 falcate, 1.1× article 2 with a comb row of setae and 3 long terminal setae. Maxilla 1, inner plate with 2 terminal plumose setae, and several fine setae on inner margin. Labium, with mandibular lobes acute; outer plate with 2 stout setae. Maxilliped, palp article 3 with a small distal protuberance. Gnathopod 1, coxa 1.4× as long as broad, anterodistal corner slightly produced, distal margin with short setae; basis 2.5× as long as broad; propodus 1.4× carpus with 2 semicircular rows of setae on anterior margin, palm defined by a robust seta. Gnathopod 2, coxa 1.6× as long as broad with short setae on distal margin; basis slender, 4× as long as broad; carpus cup-shaped, 1.5× as broad as long; propodus 2.2× as long as broad and 3.6× length of carpus, posterior margin poorly setiferous, palm sinuous, palm and posterodistal margin with strong stout robust setae; dactylus curved and about half length of propodus. Pereopod 3–4, propodus posterodistal margin with 1 striate, sabre seta and 1 short, straight, robust seta; dactylus constricted subdistally at the junction of the unguis. Pereopod 5, basis subovoid, posterior margin weakly crenulate with short robust setae. Pereopod 6, basis, posterior margin weakly convex, weakly serrated with short setae. Pereopod 7, basis posterior margin weakly convex, serrated and with short setae. Epimera 1–3, posterodistal margin produced into a small but distinct tooth. Epimera 2–3, with robust setae on the anterodistal margin. Uropod 1, peduncle 1.3× inner ramus; outer ramus 0.8× inner ramus. Uropod 2, peduncle subequal to outer ramus; outer ramus 0.8× inner ramus. Uropod 3, peduncle 0.6× outer ramus; rami subequal with robust setae on margins and apices. Telson, cleft to about 80% its length, lobes tapered, notched at tip with an acute inner tooth, each lobe with 2 robust setae.

Remarks. The present material agrees well with Walker’s description of Elasmopus spinimanus , except that the male gnathopod 2 propodus is subquadrate proximally and excavate on the posterodistal margin (subpyriform in Walker’s material). The present material also closely resembles the material described by Myers (1985) from Fiji except that in that material, the coxae of gnathopods 1 and 2 have longer setae, the excavation on the palm of the male gnathopod 2 is not well developed and the telson has more setae on the lateral margins. Fijian material examined in the present work, has the posterodistal margins of the propodus of pereopods 3 and 4 with 1 striate locking seta and 1 normal robust seta (c.f. Myers, 1985, fig. 87). The tapered and notched telson, the subequal uropods 3 and the spinous, poorly setiferous palm of gnathopod 2 taken together, distinguish this species from other Elasmopus from Mauritius.

Type locality. Sri Lanka .

Distribution. Mauritius, Sri Lanka, Fiji.