Cochinorchestia Lowry & Peart, 2010

Lowry, J. K. & Springthorpe, R. T., 2015, Coastal Talitridae (Amphipoda: Talitroidea) from north-western Australia to Darwin with a revision of the genus Cochinorchestia Lowry & Peart, 2010, Zootaxa 3985 (2), pp. 151-202 : 160

Cochinorchestia Lowry & Peart, 2010

Cochinorchestia Lowry & Peart, 2010: 21 .

Type species. Parorchestia notabilis K.H. Barnard, 1935 , original designation.

Included species. Cochinorchestia includes 7 species: C. lindsayae sp. nov.; C. metcalfeae sp. nov.; C. morini ( Peethambaran Asari, 1998) ; C. morrumbene sp. nov.; C. notabilis ( K.H. Barnard, 1935) ; C. poka sp. nov. C. tulear sp. nov.

Diagnostic description (based on male). Head eyes medium (greater than 1/5 to 1/3 head length). Antenna 1 long, reaching slightly beyond antenna 2 peduncle. Antenna 2 peduncular articles slender; peduncular article 3 without ventral process; flagellum apical article minute, virgula divina present or absent. Mandible left lacinia mobilis 4-cuspidate. Maxilliped palp article 2 distomedial lobe well developed; article 4 small, well defined. Gnathopod 1 subchelate; posterior margin of merus, carpus and propodus each with lobe covered in palmate setae. Gnathopod 2 subchelate; merus and carpus free; dactylus not modified distally, blunt. Pereopods 3–7 simplidactylate. Pereopod 4 dactylus slender, similar to pereopod 3. Pereopods 5–7 without setae along posterior margin of the dactylus. Pereopods 6–7 not sexually dimorphic, without row of short setae along posterior margin of dactyli. Pleonites 1–3 without dorsal spines. Pleopods all well developed. Epimera without slits. Uropod 1 rami without apical pear-shaped setae; outer ramus slender, with marginal robust setae. Uropod 3 well developed; ramus shorter than peduncle. Telson entire, with 2–4 apical robust setae per side.

Ecological type. Marsh-hoppers (palustral, semi-aquatic in salt marshes and mangrove swamps).

Remarks. This is the first record of the genus Cochinorchestia since it was originally described from southwestern India ( Lowry & Peart 2010). We expand its distribution to Mozambique and Madagascar in the southwestern Indian Ocean; Thailand; Ambon in eastern Indonesia; and northern Australia.

There appears to be two types of Cochinorchestia – species with a relatively simple palm on male gnathopod 2 such as C. metcalfeae sp. nov., C. morini ( Peethambaran Asari, 1998) and C. poka sp. nov., and those with a highly complex palm such as C. lindsayae sp. nov., C. morrumbene sp. nov. and C. notabilis ( K.H. Barnard, 1935) .

Cochinorchestia appears to belong to a post-Gondwanan generic complex including Eorchestia Bousfield, 1984 , Microrchestia Bousfield, 1984 and Protorchestia Bousfield, 1982 . The main difference between Cochinorchestia and the other genera is the presence of robust setae on the outer ramus of uropod 1. They share a number of basal characters such as a long first antenna, a well-defined fourth article on the mandibular palp, simplidactylate pereopods and an unmodified dactylus on pereopod 4.

There is little difference between Protorchestia Bousfield, 1982 and Microrchestia Bousfield, 1984 . The only significant differences we can find between Microrchestia and Protorchestia are the slightly sexually dimorphic pereopods 7 in Microrchestia , the maxillipedal palp article 2 is slender in Microrchestia (expanded in Protorchestia ), the lacinia mobilis is 4-cuspidate (5-cuspidate in Protorchestia ) and the pereopod 4 carpus in Microrchestia is significantly shorter than that of pereopod 3 (similar length in Protorchestia ). Richardson (1996) comments on the slight differences between the Tasmanian species of ‘ Eorchestia ’ and Protorchestia . For Richardson the main difference was the 5-dentate left lacinia mobilis of Protorchestia and this character holds for all species. These are all very small differences which make it difficult at times to separate Microrchestia and Protorchestia .