Elasmopus atollicus, Myers, A. A., 2014

Myers, A. A., 2014, Amphipoda (Crustacea) from the Chagos Archipelago, Zootaxa 3754 (1), pp. 1-31 : 1-5

Elasmopus atollicus sp. nov.

( Figs 1–3 )

Type material. Holotype male, 3.5 mm, Diego Garcia atoll, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 15.02.2012 ( OUMNH.ZC.2013.06.001). Paratypes, 1 male 1 female, same data as holotype ( OUMNH.ZC.2013.06.002).

Other material. 1 male, Diego Garcia, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 15.02.2012 ( OUMNH.ZC.2013.06.003); 1 male 1 female 1 juvenile, Diego Garcia, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 16.02.2012 ( OUMNH.ZC.2013.06.004); 2 females, Peros Banhos, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 22.02.2012 ( OUMNH.ZC.2013.06.005); 1 male 1 female, Peros Banhos, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 24.02.2012 ( OUMNH.ZC.2013.06.006); 1 female, Great Chagos Bank – Eagle Island, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 29.02.2012 ( OUMNH.ZC.2013.06.007); 2 male, 5 females, Egmont, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 0 1.03.2012 ( OUMNH.ZC.2013.06.008); 5 males 1 female, Diego Garcia, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 0 3.03.2012 ( OUMNH.ZC.2013.06.009); 1 male, 1 female, Diego Garcia, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 0 5.03.2012 ( OUMNH.ZC.2013.06.010).

Etymology. Atoll dweller, referring to the type locality.

Description. Based on male holotype, 3.5 mm.

Head. Head with rounded eye lobes and sub-ocular notch. Antenna 1 much less than half body length; articles 1 and 2 subequal in length; article 3 a little over half length of article 2; flagellum shorter than combined length of peduncular articles 2 and 3, with 10 articles; accessory flagellum with two long articles and one rudimentary terminal article. Antenna 2 shorter and more slender than antenna 1; peduncular article 4 and 5 subequal; flagellum longer than peduncular article 5 with 6 articles. Mandible palp well developed; articles 2 and 3 subequal in length; article 3 subfalcate.

Pereon. Gnathopod 1 coxa anterodistal margin forward produced; basis short, stout; propodus longer than carpus, palm oblique defined by a robust seta; dactylus fitting palm. Gnathopod 2 coxa deeper than broad, unproduced; basis stout, expanded distally, anterodistal margin with two strong robust setae; carpus very reduced, cup-shaped; propodus pyriform, narrowing distally, palm oblique continuous with posterior margin, anteroposterior margin with two submarginal spines the anterior one subsquare the medial one subtriangular; dactylus falcate, posterior margin with large rounded excavation. Pereopods 5–7 stout with broadened merus and carpus. Pereopod 7 basis with posterior margin convex and weakly crenulate.

Urosome. Epimera 1–2 posterodistal margin with small spine. Epimeron 3 posterodistal margin scalloped. Uropod 1 with numerous robust setae, rami subequal in length. Uropod 2 with robust setae, inner ramus longer than outer. Uropod 3 peduncle longer than rami, outer ramus shorter than inner. Telson strongly cleft with two robust setae on each side.

Female (sexually dimorphic characters). Gnathopod 2 basis slender without robust setae; carpus less shortened than in male, subtriangular; propodus more than twice length of carpus, lacking submarginal spines, palm oblique defined by robust seta; dactylus slender, fitting palm.

Remarks. The most similar species to E. atollicus sp. nov. appears to be E. souillacensis Appadoo & Myers, 2003 from Mauritius, but in that species the rami of uropod 3 are subequal in length. The shape of the posterior margin of the male gnathopod 2 propodus also differs in the two species. The female of E. souillacensis is unknown.

Habitat. Dead coral heads in shallow water.

Distribution. Known only from Chagos archipelago,

Figures

FIGURE 1. Elasmopus atollicus sp. nov., male, holotype, 3.5 mm, Diego Garcia.

FIGURE 2. Elasmopus atollicus sp. nov., male, holotype, 3.5 mm, female paratype, 3.5 mm, Diego Garcia.

FIGURE 3. Elasmopus atollicus sp. nov., male, holotype, 3.5 mm, Diego Garcia.