Melita setimera, Appadoo & Myers, 2005

Appadoo, C & Myers, AA, 2005, Amphipods of the Genera Ceradocus, Dulichiella, Melita and Nuuanu (Crustacea: Melitidae) from Mauritius, Indian Ocean, Records of the Australian Museum 57, pp. 221-236 : 230-235

Melita setimera n.sp.

Figs. 7–8

Type material. HOLOTYPE 3, 4.1 mm, AM P60869, 0–1 m depth, living on a mixture of Centroceras clavulatum, Hypnea sp., Gracilaria corticata , Enteromorpha flexuosa and Sargassum densifolium, Tamarin (20°19.5'S 57°22'E), Mauritius, C. Appadoo, 11 October 1999. PARATYPES: 233, 4♀♀, AM P60870, same data as holotype; 1♀ from Acanthophora spicifera, Souillac (20°31'S 57°30.7'E), 10 November 1998; 13, 1♀ from Padina sp. and Halimeda sp. , Grand Baie (20°0.5'S 57°34'E), 5 May 1999; 233, 1♀, 1 juv. from mixture of Padina sp. , Enteromorpha flexuosa, Hypnea sp., Amphiroa sp. and Caulerpa sertulariodes, Tamarin , 18 June 1999; 13, 3♀♀, 3 juv. from Amphiroa flagellisima and Padina , Ulva lactuca and Enteromorpha sp. and ashcoloured sand, Tamarin, 2 August 1999; 933, 12♀♀, 9 juv. from mixture of Centroceras clavulatum,Hypnea sp., Gracilaria corticata , Enteromorpha flexuosa and Sargassum densifolium, Tamarin , 11 October 1999.

Description. Male length, 4.3 mm. Head lacking subocular notch; eyes subround. Antenna 1 peduncle article 1 with stout robust setae on ventral margin; article 2, 1.2× article 1; article 3 slightly less than half length of article 1; accessory flagellum 2-articulate, primary flagellum 20- articulate. Antenna 2 article 5 subequal to 4, flagellum 9- articulate. Mandible palp article 3 slightly longer than article 2, article 1, 0.5× the length of article 3. Maxilla 1 inner plate with 6 apical plumose setae. Lower lip with rounded mandibular lobes. Gnathopod 1 coxa subrectangular, 1.6× as long as broad, distal margin with very short setae; basis slender, 2.9× as long as broad, with very dense patches of setae on anterior margin; propodus 0.6× length of carpus, with a hood over the dactylus; dactylus broad at base, with a small medial expansion and tapering tip. Gnathopod 2 coxa subrectangular, 1.4× as long as broad; basis slightly expanded about 2.2× as long as broad, with dense long setae on anterior margin and a few patches of setae on posterior margin; carpus cup-shaped, 1.5× as broad as long; propodus 1.3× times as long as broad, palmar margin slightly oblique, palmar border broadly sinuous; dactylus slender and 0.6× the length of propodus, dactylus closing across the medial face of propodus. Pereopod 3 coxa subrectangular, 1.5× as long as broad with short setae on ventral margin; basis slender, anterior margin concave, 3.5× as long as broad; propodus subequal to carpus; dactylus with terminal unguis and one seta on anterior margin. Pereopod 4 coxa excavate on posterior margin; other features as pereopod 3. Pereopod 5 basis, 1.5× as long as broad, anterior margin with stout robust setae, posterior margin weakly serrated and with short setae; dactylus with 1 seta on anterior margin. Pereopod 6 basis 1.4× as long as broad, otherwise like that of pereopod 5; merus and carpus with dense patches of long setae on anterior margins and short robust setae on posterior margin. Pereopod 7 similar to pereopod 6 except dense patches of setae on merus and carpus on the posterior margins and short robust setae on anterior margins. Epimeron 1 with small posterodistal tooth. Epimeron 2 weakly toothed at posterodistal margin. Epimeron 3 weakly toothed on posterodistal margin. Urosomite 1 with acute dorsal tooth, urosomite 2 with one robust seta on middorsal surface. Uropod 1 peduncle with basofacial robust seta, rami slender, 0.9× peduncle. Uropod 2 rami subequal to peduncle. Uropod 3 inner ramus rudimentary, with one or two terminal robust setae; outer ramus 1-articulate, 2× length of peduncle, spatulate, and with short robust setae and long fine setae. Telson apices pointed, each lobe with two robust setae on outer margin and two on medial hump.

Female: length, 3.8 mm (mature, with eggs). Gnathopod 1 coxa 2× as long as broad; basis slender, with patches of setae on proximal and distal anterior margins and on medial posterior margin; propodus palm transverse; dactylus

b = 0.2 mm (female G1 and male G1 and G2), c = 0.2 mm (male G2) and d = 0.2 mm (enlargement of male G2).

normal. Gnathopod 2 coxa 2.1× as long as broad; basis slender, 3× as long as broad; propodus slightly longer than carpus, palm oblique, with long setae on palmar margin and anterior margin. Pereopod 6, coxa bilobed without any finger-like protuberance. Female pereopods 6 and 7 without dense setae on merus and carpus.

Remarks. This species most closely resembles Melita simplex Myers (1985) from Fiji, in having an acute dorsal tooth on urosomite 1 and a non sexually-dimorphic female coxa 6. Melita setimera male gnathopod 1, however, has a densely setose distal margin on the basis, the propodus is shorter than the carpus and it has a lobe above the dactylus. The male gnathopod 2 propodus of M. setimera has parallel margins and the palmar border is broadly sinuous whereas the ventral margin of male gnathopod 2 of M. simplex is evenly convex. Pereopods 6 and 7 merus and carpus are densely setose in M. setimera , but this character state is unknown in Melita simplex . The telson apices of M. simplex have a terminal robust seta that is lacking in M. setimera .

Melita setimera can be distinguished from all other species of Melita from Mauritius, by the presence of the dorsal tooth on urosomite 1 on both males and females. Males are easily distinguished by the broadly sinuous palmar margin of gnathopod 2 and the presence of dense long setae on merus of pereopods 6 and 7.

Habitat. Melita setimera was collected only at Tamarin at depths of less than 1 m. The site has some freshwater influence due to a river flowing in the vicinity.

Type locality. Tamarin , Mauritius .

Distribution. Mauritius.

Etymology. From the Latin saeta = bristle coupled with merus referring to the strongly setose merus of male pereopods 6 and 7.