Austropacifica, Lowry & Springthorpe, 2019

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 : 358

Austropacifica gen. nov.

Type species. Orchestia monospina Stephensen, 1935 , original designation.

Included species. Austropacifica contains 4 species: A. australis ( Lowry & Springthorpe, 2009c) ; A. monospina ( Stephensen, 1935) ; A. pectenispina ( Bousfield, 1970) ; A. serejoae ( Lowry & Springthorpe, 2015a) .

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

Etymology. Named for the distribution of the genus confined to the South Pacific Ocean.

Diagnostic description (based on male). Head. Eye medium (1/5–1/3 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 5- or 4-cuspidate. Maxilliped palp article 2 with distomedial lobe; article 4 reduced, button-shaped.

Pereon. Gnathopod 1 subchelate; posterior margin of merus, carpus and propodus each with lobe covered in palmate setae; palm transverse. Gnathopod 2 subchelate; posterior margin of merus, carpus and propodus each without lobe covered in palmate setae; dactylus attenuated distally, shorter than propodus; palm acute. Pereopods 3–7 bi-cuspidactylate. Pereopod 4 dactylus thickened proximally with notch midway along posterior margin. Pereopod 6 shorter than pereopod 7. Pereopod 7 not sexually dimorphic (no articles expanded). Female—oostegites setae with simple smooth tips.

Pleon. Pleonites 1–3 without dorsal spines. Pleopods all well developed. Epimera 1–3 slits present on at least one plate. Uropod 1 peduncle distolateral robust seta present, with simple tip; endopod with marginal robust setae in 1 row; exopod with one long mid-medial seta. Uropod 2 rami without apical spear-shaped setae; endopod with marginal robust setae in 1 row; exopod with marginal robust setae in 1 row. Uropod 3 ramus subequal in length to peduncle, or shorter than peduncle. Telson as broad as long, telson tapering distally, apically incised, with 3–6 robust setae per lobe.

Remarks. Austropacifica is most similar to Floresorchestia . In species of Austropacifica the margin of the exopod of uropod 1 in adult males has a large mid-medial robust seta with a modified tip (looking like a sponge), possibly associated with sperm-transfer, but this has not been observed, and not found in species of Floresorchestia . In other respects the genera are the same.

Both genera appear to be closely related to the Australian marsh-hopper Tropicorchestia . The only significant morphological difference between these genera appears to be the lack of vertical slits on the epimeral plates and the apically incised telson in Tropicorchestia .