Elasmopus pseudinteger, Chandani Appadoo, 2003

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 : 67

Elasmopus pseudinteger n.sp.

Figs. 5, 6

Elasmopus hooheno .– Ledoyer, 1978: 269.–Appadoo & Steele, 1998: 639.

Not E. hooheno J.L. Barnard, 1970: 121 , fig. 70.

Type material. HOLOTYPE: 3, 5.2 mm, from the alga Acanthophora spicifera, Anse la Raie (19°59.5'S 57°37.5'E), 15 May 1998, AM P60544 . PARATYPES: 533, 8♀♀, same data as holotype, AM P60545 .

Additional material examined. 13, 3♀♀, 5 juv., from Acanthophora spicifera, Anse la Raie , 15 May 1998. 633, 6♀♀, 5 juv., from Jania sp. and Valonia sp. , Bain Boeuf (19°59'S 57°36'E), 28 Aug. 1998. 6♀♀, 5 juv., from mixture of Caulerpa racemosa , Digenia simplex and Jania adherens, Roches Noires (20°6.2'S 57°44.5'E), 9 Apr. 1999. 13, 3♀♀, 4 juv., from Laurencia papillosa, Anse la Raie , 24 Jan. 2000. 13, 5♀♀, 1 juv., from mixture of Padina sp. , Gracilaria salicornia , Ulva lactuca, Hypnea cornuta and Dictyota divaricata, Choisy (20°01'S 57°32.7'E), 25 Jan. 2000.

Description. Male: Length, 3.9 mm. Body, with 1 or 2 groups of setae on dorsum, pereon and pleon. Head, with rudimentary subocular notch; eyes large and subround with ring of clear ommatidia and a dark core. Antenna 1, peduncle articles 1 and 2 subequal; article 3, 0.6× article 1; accessory flagellum 1-articulate; primary flagellum 19- articulate. Antenna 2, articles 4 and 5 subequal; flagellum 7-articulate. Mandible, palp article 2 with 1 medial and 2 distal setae; article 3 falcate, 1.4× article 2, with comb row of setae and 3 long terminal setae. Maxilla 1, inner plate with 2 terminal plumose setae and fine setae on inner margin. Labium with mandibular lobes acute; outer plate with blunt stout seta on inner margin. Maxilliped, palp article 3 with a small protuberance at distal end. Gnathopod 1, coxa subquadrate, 1.2× as long as broad, distal margin with setae reaching abut half length of coxa; basis slightly expanded, 2.3× as long as broad, with a group of long setae on the posterior margin; propodus subequal to carpus, palm defined by a robust seta, anterior margin with 2 groups of setae. Gnathopod 2, coxa 1.3× as long as broad, distal margin with a group of setae about half the length of the coxa; basis 2.2× as long as broad, posterior margin with 4 long setae, distal end of anterior margin with about 5 robust setae; carpus cup-shaped, twice as broad as long; propodus 4× length of carpus, narrower distally, posterior margin poorly setiferous, inner face with 2 distal processes and 1 medial process between which is a pit for reception of the dactylar tip; dactylus falciform. Pereopods 3–4, basis 3.2× as long as broad; propodus posterodistal margin with 1 striate sabre seta and 1 normal robust seta; dactylus distally constricted. Pereopod 5, basis broad, posterior margin crenulate distally, with both short and very long setae; merus and carpus expanded, about as broad as long. Pereopod 6, basis almost as broad as long, posterior margin crenulate distally, with short and very long setae. Pereopod 7, basis posterior margin convex, crenulate with short and very long setae. Epimeron 1, subquadrate. Epimeron 2, posterodistal margin produced into a small tooth, distal margin with a few setae. Epimeron 3, posterodistal margin weakly scalloped with short setae, distal margin with several well-developed setae. Uropod 1, peduncle 1.3× rami; rami subequal. Uropod 2, peduncle subequal to inner ramus; inner ramus 1.1× outer ramus. Uropod 3, peduncle subequal to outer ramus; outer ramus 1.2× inner ramus; inner ramus with only terminal robust setae. Telson, subquadrate, as long as broad, uncleft, with 2 stout robust setae on each side.

Female secondary sexual characters: length, 3 mm (ovigerous). Gnathopod 1, coxa a little deeper and basis a little longer than that of male; propodus 1.2× length of carpus. Gnathopod 2, coxa 1.5× as long as broad; basis 2.7× as long as broad; propodus 1.8× carpus; palmar margin with defining robust seta.

Remarks. This species closely resembles Elasmopus integer Myers (1989) from the Society Islands. However, Elasmopus pseudinteger differs from E. integer in the 1-articulate accessory flagellum (two articulate in E. intiger ); the more slender mandibular palp with less setiferous article 2; the more setiferous basis of pereopods 5 to 7; the scalloped posterodistal margin of epimeron 3 (evenly convex with small posterodistal tooth in E. integer )and in the evenly convex posterior margin of the telson (with dorsodistal depression in E. integer ).

An entire (uncleft) telson is known only in two other species of Elasmopus , E. integer Myers from the Society Islands and E. takamotus Myers (1986) from Niue Island. Elasmopus pseudinteger is thus easily distinguished from all other Elasmopus species in Mauritius.

Habitat. This species was found mostly among red algae along the north and northeast coast of Mauritius.

Type locality. Anse la Raie , Mauritius .

Distribution. Known only from Mauritius.

Etymology. From the Latin pseudo —false and integer , the name of a closely related species.