Elasmopus ora, Myers, A. A., 2014

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

Elasmopus ora sp. nov.

( Figs 4 , 5 )

Type material. Holotype male, 4.6 mm, Great Chagos Bank, Brothers Island, outer reef, dead branching coral heads, 10 m. C. Head and H. Koldewey, 27.02.2012 ( OUMNH.ZC.2013.06.011). Paratypes 2 females, same data as holotype ( OUMNH.ZC.2013.06.012).

Etymology. ora = Latin, ledge, referring to the short overhanging palm of the male gnathopod 2.

Description. Based on male holotype, 4.6 mm.

Head. Head eye lobes rounded with subocular notch. Antenna 1 two thirds body length; peduncular article 1 a little longer than article 2; flagellum subequal in length with peduncle with 18 articles; accessory flagellum with two long articles and one rudimentary terminal article. Antenna 2 shorter than antenna 1; peduncular article 5 shorter than 4; flagellum with 8 articles. Mandible palp articles 2 and 3 subequal in length; article 3 falcate.

Pereon. Gnathopod 1 coxa produced anteriorly; propodus longer than carpus, palm oblique. Gnathopod 2 coxa deeper than broad, unproduced; basis slender, 4 × as long as broad; carpus reduced, cup-shaped; propodus elongate subovoid, palm a short shelf bearing four strong robust setae, proximal to which is a shallow depression; dactylus fitting palm. Pereopod 3 propodus posterodistal margin with strong curved robust seta. Pereopods 5–6 basis posterior margin weakly concave. Pereopod 7 basis evenly convex, very weakly notched.

Pleon. Epimera 1–3 each with posterodistal spine, that of epimeron 3 the largest. Uropod 1 with many robust setae; rami subequal, a little shorter than peduncle. Uropod 2 inner ramus longer than outer and longer than peduncle. Uropod 3 rami slender longer than peduncle, inner ramus longer than outer. Telson deeply notched, with bifid lobe terminations and bearing two unequal setae on each lobe.

Female (sexually dimorphic characters). Gnathopod 2 carpus less reduced that in male; propodus more slender than in male and with oblique regular palm.

Remarks. Elasmopus ora resembles E. mcluerensis Hughes & Lowry, 2011 from the Australian Northern Territories. It differs markedly in the third uropod, which is relatively elongate and slender in E. ora but short and stout in E. mcluerensis . In addition, the telson shape is a little different in the two species and bears two setae on each side in E. ora but four setae on each side in E. mcluerensis . The uropod 3 is similar to that of E. gracilis Schellenberg, 1938 , but in that species the posterior margin of the propodus in the male gnathopod 2 is clothed in dense long setae.

Elasmopus pectenicrus Bate, 1862 , has a similar shaped male gnathopod 2, but the propodus of that appendage is clothed in dense long setae on the posterior margin and the basis of pereopod 6 in that species is crenulate along the posterodistal margin.

Habitat. Dead coral heads in shallow water.

Distribution. Known only from Chagos archipelago.

Figures

FIGURE 4. Elasmopus ora sp. nov., male, holotype, 4.6 mm, female, paratype, 4.5 mm, Great Chagos Bank.

FIGURE 5. Elasmopus ora sp nov., male, holotype, 4.6 mm, Great Chagos Bank.