The genus Elasmopus (Crustacea: Amphipoda: Maeridae) in Australian waters Author Hughes, L. E. Author Lowry, J. K. text Journal of Natural History 2011 2011-03-31 45 9 - 10 579 628 http://dx.doi.org/10.1080/00222933.2010.534825 journal article 10.1080/00222933.2010.534825 1464-5262 4652513 Elasmopus arafura sp. nov. ( Figures 1 , 2 ) Type locality Reef at west end Oxley Island, Northern Territory , Arafura Sea, Australia (11 ◦ 00 ′ S, 132 ◦ 49 ′ E). Type material Holotype male, 6.0 mm, dissected, three slides, AM P.78273, reef west end Oxley Island , Northern Territory , Arafura Sea , Australia (11 ◦ 00 ′ S, 132 ◦ 49 ′ E), 5 m , red sponge on dead coral Acropora sp., hand collected on SCUBA , 20 October 1982 , coll. J.K. Lowry (NT 79). Figure 1. Elasmopus arafura sp. nov. , holotype male, 6.0 mm AM P.78273, Oxley Island, Northern Territory, Arafura Sea. Figure 2. Elasmopus arafura sp. nov. , holotype male, 6.0 mm AM P.78273, Oxley Island, Northern Territory, Arafura Sea. Additional material examined Western Australia : 9 specimens , AM P.79350, outer Ningaloo Reef , off Neds Camp , Cape Range National Park (21 ◦ 59 ′ 30 ′′ S, 113 ◦ 54 ′ 30 ′′ E), 2 m , small brown dictyotalean alga, hand collected on SCUBA , 1 January 1984 , coll. J.K. Lowry and R . T . Springthorpe (WA 342) ; 14 specimens , AM P.80012, Tantabiddy Creek , Ningaloo (21 ◦ 54 ′ 46 ′′ S, 113 ◦ 58 ′ 13 ′′ E), 0 m, sand, June 2008 , coll. N.L. Bruce (MI WA 968) ; 20 specimens , AM P.80016, southern side of pass, Ningaloo Reef (21 ◦ 55 ′ 6 ′′ S, 113 ◦ 57 ′ 37 ′′ E), coarse sediment, collected by hand on SCUBA , 3 m , 10 June 2008 , coll. N.L. Bruce and M. Blazewicz-Paszkowycz (MI WA 972) ; 3 specimens , AM P.80015, southern side of pass, Ningaloo Reef (21 ◦ 55 ′ 6 ′′ S, 113 ◦ 57 ′ 37 ′′ E), coarse sediment, collected by hand on SCUBA , 2 m , 8 June 2008 , coll. N.L. Bruce and M. Blazewicz-Paszkowycz (MI WA 971) . Etymology Named for the Arafura Sea, where this species was first collected. Description Based on holotype male, 6.0 mm, AM P.78273. Head. Eyes subovoid; lateral cephalic lobe broad, truncated, anteroventral margin with notch / slit. Antenna 1 longer than antenna 2; peduncular article 1 subequal in length to article 2, with 1 robust seta on posterior margin ; article 2 longer than article 3; flagellum with 27 articles; accessory flagellum short, tri-articulate. Antenna 2 peduncular article 2 cone gland not reaching to end of peduncular article 3; article 4 subequal in length to article 5; flagellum with eight articles. Mandible molar well developed, triturative, accessory setal row with three setae; palp tri-articulate; article 1 about twice as long as broad, shorter than article 2; article 2 longer than article 3, with few slender setae; article 3 strongly falcate, short (about 2.5 times as long as broad), longer than article 1, with comb of short robust setae along anterodistal margin and three apical setae. Lower lip unknown. Maxilla 1 inner plate subquadrate, with two apical plumose setae. Pereon. Gnathopod 1 coxa anterior margin straight, anteroventral corner produced, rounded; merus without posterodistal tooth; carpus about 1.5 times as long as broad, subequal in length to propodus, not heavily setose; propodus anterior margin with few rows of long slender setae, medial surface without setal comb, palm acute, convex, entire, defined by posterodistal corner, with posterodistal robust seta. Gnathopod 2 subchelate; basis slender, anterodistal corner excavate with group of five robust setae ; merus with subquadrate distoventral corner; carpus compressed, lobate, projecting between merus and propodus; propodus expanded, anterior margin with rows of short slender setae, posterior margin with a few clusters of long slender setae, palm about half length of propodus, acute, sculptured, palm distomedial shelf subrectangular with group of robust setae , proximal subacute tooth and palm defining posteroventral tooth , subpalmar surface smooth; dactylus closing along and reaching end of palm, apically subacute. Pereopod 4 coxa posteroventral lobe well developed, with rounded posteromedial corner. Pereopods 5–7 narrow distally; basis posterior margin slightly expanded convex, weakly crenulate , with many long stiff slender setae ; carpus and propodus with many long, slender setae along margins; propodus not expanded posterodistally; dactylar unguis simple. Pleon. Epimera 1–3 posteroventral corner with small subacute tooth. Urosomite 1 smooth, without carina. Uropod 1 peduncle with 1 basofacial robust seta; rami subequal in length; inner ramus about as long as peduncle. Uropod 2 rami subequal; inner ramus subequal in length to peduncle. Uropod 3 rami distally truncated, apical robust setae short; inner ramus long (twice as long as broad), shorter in length than outer ramus; outer ramus shorter than peduncle. Telson moderately cleft (30–66% cleft), broader than long, apical lobes with rounded inner and short outer apical cusp, each lobe with two or three short and long dorsal robust setae, with pair of lateral plumose setae. Remarks Many specimens of E. arafura sp. nov. were examined under slides to confirm that the species-level character of uropod 1 peduncle with 2 basofacial setae was not an aberration or misdiagnosis of a newly-forming moult stage. Elasmopus arafura sp. nov. should be considered as a cryptic species within the E. rapax complex. Elasmopus arafura sp. nov. is similar to E. hooheno , E. integer Myers 1989 and E. rapax juveniles in the male gnathopod 2 propodus palm with two teeth and pereopods 5–7 basis posterior margin lined with long stiff slender setae. Elasmopus arafura sp. nov. differs from these three species in the tri-articulate accessory flagellum, gnathopod 2 basis small distal excavation in adult males and uropod 1 peduncle with two basofacial robust setae. A distal cluster of robust setae on the gnathopod 2 basis is also present on E. integer and E. hooheno though greater in length in these species. Elasmopus arafura sp. nov. and E. integer are most readily separated by the telson, which is cleft and entire, respectively. Elasmopus arafura sp. nov. epimeron 3 distoventral corner has a small acute tooth while in E. hooheno the corner is rounded. Distribution Australia . Northern Territory : Oxley Island (current study) . Western Australia : Ningaloo Reef (current study).