Microrchestia Bousfield, 1984

Lowry, J. K. & Peart, R., 2010, The genus Microrchestia (Amphipoda: Talitridae) in eastern Australia, Zootaxa 2349 (1), pp. 21-38 : 22-23

Microrchestia Bousfield, 1984

Microrchestia Bousfield, 1984: 202 (in part).

Type species. Parorchestia macrochela Bousfield, 1971 , original designation.

Diagnosis. Antenna 1 elongate, as long as antenna 2 peduncle. Mandible left lacinia mobilis 4 dentate. Maxilliped palp article 2 without medial lobe; article 4 small, but distinct. Gnathopod 1 subchelate; posterior margins of merus, carpus and propodus each with lobe covered in palmate setae. Gnathopod 2 subchelate in male, mitten-shaped in female. Pereopods 7 sexually dimorphic. Pleopods well developed. Uropods 1–2 outer ramus without robust setae. Uropod 3 ramus shorter than peduncle. Telson entire or apically incised, with 2 to 6 apical setae.

Included species. Microrchestia includes 4 species: M. bousfieldi sp. nov.; M. macrochela ( Bousfield, 1971) ; M. similis ( Bousfield, 1971) ; M. watsonae sp. nov.

Remarks. Based on following set of characters (maxilliped with a reduced, but distinct palp article 4; gnathopod 1 merus, carpus and propodus each with patch of palmate setae; gnathopods 1 and 2 subchelate in male; pereopods 3 to 7 simplidactylate; pereopod 4 dactylus similar to that of pereopod 3; pleopods well developed; and telson entire or apically incised, with apical setae only) Microrchestia appears most similar to the following group of post-gondwanan genera— Chiltonorchestia from New Caledonia; Cochinorchestia from south-eastern India and eastern Africa; Eorchestia from southern Africa and south-eastern Australia; Neorchestia from Tasmania and Protorchestia from southern New Zealand, southern Australia and apparently southern South America.

All of these genera have a relatively well developed antenna 1, but in two genera, Cochinorchestia and Microrchestia it reaches to the end of or slightly beyond the antenna 2 peduncle. Among these genera only Cochinorchestia has robust setae on the outer ramus of uropod 1. Chiltonorchestia , Microrchestia and Neorchestia have a 4-toothed left lacinia mobilis and Cochinorchestia , Microrchestia and Neorchestia all have the ramus of uropod 3 shorter than the peduncle. A phylogenetic analysis is needed to resolve the sister taxon relationships within this generic group.

Distribution. Microrchestia is currently known from northern Papua New Guinea and eastern Australia.