Ampithoe mascarenensis, Appadoo & Myers, 2004

Appadoo, C & Myers, A. A., 2004, Corophiidea (Crustacea: Amphipoda) from Mauritius, Records of the Australian Museum 56 (3), pp. 331-362 : 340-342

Ampithoe mascarenensis n.sp.

Figs. 10–12

Ampithoe sp. 2 (Appadoo & Steele, 1998: 639).

Type material. HOLOTYPE 3, 5.5 mm, AM P65848, from Centroceras clavulatum, Souillac (20°31'S 57°30.7'E),

depth less than 1 m, C. Appadoo, 13 August 1998. PARATYPES, 1♀, 4.3 mm, AM P65849, 13, AM P60598, 433 and 10♀♀, AM P60610, same data as holotype; 333, 12♀♀, 6 juv., AM P60611, from Centroceras clavulatum ; 13, 1 juv., AM P60612, from Digenia simplex, Souillac (20°31'S 57°30.7'E), 13 August 1998; 13 from Amansia glomerata, AM P 60613, Souillac, 4 August 1999; 333, 4♀♀, 4 juv., AM P60614, from Digenia simplex , Padina sp. and Jania adherens, Roches Noires (20°6.2'S 57°44.5'E), 6 August 1999; 233, 11♀♀, 2 juv., AM P60615, from Digenia simplex , Padina sp. , Jania adherens , Sargassum densifolium, Roches Noires , 15 October 1999.

Description. Male, 5.2 mm. Head 1.2× as long as deep, disto-ventral margin weakly recessed; eyes of medium size with well-developed ommatidial ring surrounding a dark central core (reddish brown in alcohol). Antenna 1, 1.3× as long as antenna 2, peduncle articles 1 and 2 subequal; article 3, 0.4× article 1; primary flagellum 29-articulate and bearing aesthetacs. Antenna 2 robust, peduncle articles 4 and 5 posterior margins with groups of plumose setae, peduncle article 4, 2.4× as long as broad; article 5, 3.7× as long as broad, 0.9× length of article 4; flagellum 13-articulate, moderately setose. Mandible palp well developed, article 3, 0.7× article 1, with apical setae. Lower lip outer lobe strongly notched, mandibular lobes rounded. Maxilla 1 inner plate small, subtriangular. Maxilla 2 inner plate narrow, with setae at apex and on inner margin; outer plate broad with apico-medial setae. Maxilliped palp article 4 subquadrate with terminal nail. Gnathopod 1 coxa 0.8× as broad as deep, anterodistal margin weakly produced, rounded, distal margin with few very short setae; basis 3× as long as broad, anterodistal lobe well developed; carpus subtriangular, as long as broad; propodus 1.7× as long as broad, palm weakly sinuous with a large medial posterodistal robust seta; dactylus robust, inner margin toothed. Gnathopod 2 robust, coxa 1.2× as broad as deep, distal margin with a few short setae; basis 2.2× as long as broad with well-developed anterodistal lobe; carpus subtriangular, 0.7× as long as broad; propodus 1.3× s long as broad, slightly expanded at the anterodistal margin, anterior margin with short setae, posterior margin with few groups of setae, inner face with one robust seta palm with a small excavation close to base of dactylus, palm sub-straight,; dactylus robust reaching end of palm. Pereopods 3 and 4 similar; coxa subrectangular, 1.3× as long as broad, distal margin with very short setae; basis slightly expanded, 2× as long as broad; merus 1.5× as long as broad; carpus and merus subequal; propodus 1.2× carpus. Pereopod 5 coxa as broad as deep, with small posterior lobe; basis expanded, about as broad as long, carpus subquadrate, subequal to merus; propodus 3.8× as long as broad, slightly expanded distally with 3 distal robust setae. Pereopods 6–7 similar, coxa broader than deep; basis slightly expanded, 1.4× as long as broad, posterior margin with a small excavation at the posterodistal corner; carpus subquadrate, 0.9× as long as merus; propodus 3.3× as long as broad, distally expanded, posterior distal margin with robust setae. Epimera 1–3 posterodistal margin rounded. Uropod 1 peduncle without interramal process, inner margin with robust setae, outer margin with fine slender setae; rami subequal and 0.6× length of peduncle. Uropod 2 rami subequal, 0.7× length of peduncle. Uropod 3 peduncle short, 1.2× as long as broad with few long slender seta on inner margin, with robust setae at the distal margin; outer ramus with a group of medial slender setae and 2 apical recurved robust setae; inner ramus 0.6× peduncle with apical slender and 5 robust setae. Telson subtriangular, distally rounded, telsonic cusps well developed, a few slender setae on medial face and lateral margins.

Female, 4.3 mm (ovigerous). Gnathopod 1 coxa 1.3× as long as broad, anterodistal margin weakly produced; basis 2.4× as long as broad, anterodistal lobe moderately developed; carpus subtriangular, 1.4× as long as broad; propodus 1.7× as long as broad, posterodistal margin with one robust seta, palm oblique; dactylus inner margin toothed. Gnathopod 2 coxa 1.4× as long as broad; basis 2.9× as long as broad, with well-developed anterodistal lobe; carpus 0.9× as long as broad; propodus 1.6× s long as broad, palm oblique with one robust seta at posterodistal corner; dactylus fitting palm, inner margin toothed.

Type locality. Souillac , Mauritius .

Distribution. Mauritius.

Habitat. This species was collected mostly amongst red algae at depths of less than 1 m. It occurred on sites that are exposed to heavy wave action (Souillac, Gris-Gris and Roches Noires).

Remarks. The presence of dense plumose setae on the peduncle of antennae 2 makes this species superficially similar to Plumithoe hirsuta ( Ledoyer, 1978) and Plumithoe plumicornis ( Ledoyer, 1979) . It differs from both these species, however, by the absence of a peduncular process on uropod 1. Ampithoe mascarenensis n.sp. resembles Ampithoe laxipodus n.sp., by the subrectangular propodus in the male gnathopod 2 and the shape of the basis of pereopods 6 and 7. The two species differ in the antenna 2: A. mascarenensis has a densely setose antenna 2 as compared to a moderately setiferous one in A. laxipodus . The males of the two species also differ in the male gnathopod 1, in A. laxipodus the basis has groups of long setae and the propodus is globular as compared to a poorly setiferous basis and a slender propodus in A. mascarenensis . The male gnathopod 2 of the two species differ; A. laxipodus has a small medial subrectangular process on the palm, a feature not present in A. mascarenensis .

Etymology. Named after the Mascarene islands: Mauritius, Reunion and Rodrigues.