Talorchestia Dana, 1852b

Lowry, J. K. & Springthorpe, R. T., 2019, Talitrid amphipods from India, East Africa and the Red Sea (Amphipoda, Senticaudata, Talitroidea, Talitridae), Zootaxa 4638 (3), pp. 351-378 : 363-364

Talorchestia Dana, 1852b

Scamballa White, 1847: 86 .

Talorchestia Dana, 1852b: 310 .―Dana, 1853: 851.―Stebbing, 1906a: 543 (partim.).―Stephensen, 1948: 7 (in part).―Hurley, 1956: 359 (in part.).―Morino & Miyamoto, 1988: 91.― Miyamoto & Morino, 1999: 170.―Lowry & Springthorpe, 2009: 905.

Type species. Talitrus gracilis Dana, 1852a , monotypy.

Included species. Talorchestia includes 18 species: T. affinis Maccagno, 1936 ; T. anakao sp. nov.; T. brucei Lowry & Springthorpe, 2009c ; T. bunaken Lowry, Springthorpe & Azman, 2017 ; T. dampieri Lowry & Springthorpe, 2015b ; T. dili Lowry, Springthorpe & Azman, 2017 ; T. gracilis ( Dana, 1852a) ; T. martensii ( Weber, 1892) (of Mi- yamoto & Morino 1999); T. mindorensis Oleröd, 1970 ; T. morinoi Othman & Azman, 2007 ; T. qeshm Lowry & Momtazi, 2015 ; T. seringat Lowry, Springthorpe & Azman, 2017 ; T. sipadan Lowry, Springthorpe & Azman, 2017 ; T. spinipalma ( Dana, 1852a) ; T. terraereginae Haswell, 1880 ; T. vietnamica ( Dang & Le, 2011) ; T. yoyoae Lowry, Springthorpe & Azman, 2017 ; T. sp. (based on T. martensii of Chilton, 1921).

Ecological type. Beach-hoppers (mainly coastal supralittoral/intertidal leaf-litter/wrack, non-substrate modifying talitrids).

Diagnostic description. Head. Eye medium (1/5–1/3 head length) or large (greater than 1/3 head length). Antenna 1 short, rarely longer than peduncular article 4 of antenna 2. Antenna 2 peduncular articles slender; article 3 without plate or process ventrally. Mandible left lacinia mobilis 6- or 5-cuspidate (sixth minute). Maxilliped palp article 2 with distomedial lobe; article 4 fused with article 3.

Pereon. Gnathopod 1 sexually dimorphic; simple or parachelate; posterior margin of carpus and propodus each with lobe covered in palmate setae; palm transverse or obtuse. Gnathopod 2 sexually dimorphic; subchelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; propodus palm angle acute; dactylus not modified distally, blunt. Pereopods 3–7 bi-cuspidactylate. Pereopod 4 dactylus thickened proximally with notch midway along posterior margin. Pereopod 5 dactylus long, slender, not inflated. Pereopod 6 not sexually dimorphic. Pereopod 6 shorter than pereopod 7, or subequal in length to pereopod 7. Pereopod 7 not sexually dimorphic (no articles expanded).

Pleon. Pleonites 1–3 without dorsal spines. Pleopods all well developed. Uropod 1 peduncle distolateral robust seta present or absent, with simple tip; rami without apical spear-shaped setae; endopod with marginal robust setae in 1 or 2 rows; exopod without marginal robust setae. Uropod 2 rami without apical spear-shaped setae; endopod with marginal robust setae in 1 or 2 rows; exopod with marginal robust setae in 1 row. Uropod 3 ramus subequal in length to peduncle or shorter than peduncle. Telson longer than broad, tapering distally, apically incised or notched, with 6 to 10+ marginal and apical robust setae per lobe.

Female (sexually dimorphic characters). Gnathopod 1 simple; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae. Gnathopod 2 mitten-shaped; basis expanded anteromedially. Oostegites on gnathopod 2 to pereopod 5.

Remarks. Lowry & Myers (2019) recently removed a number of species from Talorchestia and those changes are recognised here.

It is difficult to know where Talorchestia fits with other talitrid genera, but based on the above diagnostic characters it might be related to the western Indian Ocean genus Persianorchestia Momtazi, Lowry & Hekmatara, 2017 and/or the north-western Pacific genus Sinorchestia Miyamoto & Morino, 1999 . Talorchestia differs from Persianorchestia in having the dactylus of pereopod 4 thickened proximally with notch midway along posterior margin (slender, similar to pereopod 3 in Persianorchestia ) and in having simple apical robust setae on the rami of uropods 1 and 2 (spear-shaped in Persianorchestia ). Talorchestia differs from Sinorchestia in having a slender second antenna (incrassate in Sinorchestia ) and no ventral plate on peduncular article 3 of antenna 2 (present in Sinorchestia ).

In characters that are known Vietorchestia Dang & Le, 2011 is very similar to Talorchestia , but probably not the same genus. Vietorchestia has a distinctively shaped gnathopod 2. Several characters separate these two genera: the development of maxilliped palp article 2 which has a well-developed medial lobe in Talorchestia (secondarily absent in Vietorchestia ), the palm of gnathopod 2 which is acute in Talorchestia (transverse in Vietorchestia ) and the uropod 2 endopod with one row of marginal robust setae in Vietorchestia (one or two rows in Talorchestia ).