Notorchestia, Serejo & Lowry, 2008

Serejo, C. S. & Lowry, J. K., 2008, The Coastal Talitridae (Amphipoda: Talitroidea) of Southern and Western Australia, with Comments on Platorchestia platensis (Krøyer, 1845), Records of the Australian Museum 60 (2), pp. 161-206 : 175

Notorchestia n.gen.

Orchestia J.L. Barnard, 1969: 470 (partim).

Talorchestia Dana, 1852: 851 .– Stebbing, 1906: 543 (partim).– Stephensen, 1948: 7 (partim).–J.L. Barnard, 1969: 472 (partim.).

Type species. Notorchestia lobata n.sp.

Etymology. Noto means southern and refers to the distribution of the genus, attached to the stem Orchestia from the Greek orchestes = dancer.

Diagnosis. Antenna 2 not geniculate and not sexually dimorphic. Mandible left lacinia mobilis 4 or 5 dentate. Maxillipedal palp dactylus present, reduced. Gnathopod 2 subchelate; basis slightly expanded; propodus palm posterodistal corner with or without protuberance. Pereopods 3–7 cuspidactylate, dactylus with row or patch of dorsal setae. Pereopod 4 carpus similar in length to pereopod 3 carpus. Pereopod 6 not sexually dimorphic. Pereopod 7 sexually dimorphic or not; basis lateral sulcus present or absent, if present very pronounced. Gills lobate and/or convoluted; gills 3–5 smaller than gills 2 and 6. Oostegites 2–5 setae with simple and multi-furcate tips. Pleopods all well developed. Uropods 1–2 outer rami with marginal robust setae. Telson cleft, longer than broad with 3–5 robust setae per lobe.

Species composition. Notorchestia contains 4 species: N. australis ( Fearn-Wannan, 1968) ; N. lobata n.sp.; N. naturaliste n.sp. and N. novaehollandiae ( Stebbing, 1899) .

Remarks. The weakness of the definition of Orchestia and Talorchestia based on the female gnathopod 2 chelation is herein reconfirmed. A restricted definition of Talorchestia (sensu stricto) was proposed by Morino and Miyamoto (1988) and Miyamoto and Morino (1999), but this is incomplete because it leaves a large number of species with no generic name. A revision of the whole complex is still needed. Some species within Notorchestia were part of the Talorchestia (sensu lato) group, a wide complex currently including about 35 species. We move eight species to Bellorchestia and two to Notorchestia , reducing the number of unplaced species to 25.

Notorchestia n.gen. is endemic to Australia, and its species show new characters for the Talitridae in general, such as the dactylus of pereopod 3–7 with a dorsal row of setae ( Figs 14 , 18 ), the multi-furcate tip setae on oostegites 2–5 ( Fig. 12 , 16 , 20 ) and a clearly cleft telson ( Fig. 11 , 15 , 19 ). Notorchestia is a member of the 4-dentate left lacinia mobilis group. The one exception is found in N. australis , which has a 4 or 5-dentate left lacinia. Not all of the diagnostic characters were observed in N. novaehollandiae , but the lateral sulcus on the basis of pereopod 7 and cleft telson strongly suggests that this species is part of this genus.

Figures

Fig. 14. Notorchestia lobata n.sp., holotype male, 10.8 mm, AM P69051, Goolwa Beach, Encounter Bay, South Australia. Scales represent 0.5 mm.

Fig. 18. Notorchestia naturaliste n.sp., holotype male, 14.8 mm, AM P69121, Bunker Bay, Cape Naturaliste, Western Australia. Scales for G1 and P4: 0.2 mm; remainder: 0.5 mm.

Fig. 12. Notorchestia australis (Fearn-Wannan, 1968), female, 11.1 mm, O2–5 and BR2–6,AM P69009; male, 16.1

Fig.16. Notorchestia lobata n.sp., paratype female, 11.0 mm, O2–5, AM P69052; holotype male, 10.8 mm, PL1–3 and BR2–6, AM P69051. Scales represent 0.5 mm.

Fig. 20. Notorchestia naturaliste n.sp. paratype female 14.6 mm, O2–5, BR2–6, AM P69124, holotype male, 14.8 mm, PL1–3, AM P69121, Bunker Bay, Cape Natu- raliste, Western Australia. Scales represent 0.2 mm.

Fig. 11. Notorchestia australis (Fearn-Wannan, 1968), male, 16.1 mm, EP1–3, U1–3, T, AM P69007; female 11.1 mm, G1–2, P7, AM P69009, Port Macdonnell, South Australia. Scales for U3 and T: 0.1 mm; G1–2 and P7: 0.2 mm; EP1–3 and U1–2: 0.5 mm.

Fig. 15. Notorchestia lobata n.sp., holotype male, 10.8 mm, U3 and T, AM P69051; female, 9.1 mm, G1, AM P60956; female 11 mm, G2 and P7, AM P69052, juvenile male, 10 mm, G2, AM P69053, Goolwa Beach, Encounter Bay, South Australia. Scales for G1, G2, P7, U1–3: 0.3 mm; EP1–3: 1 mm; merus (juvenile) and T: 0.2 mm.

Fig. 19. Notorchestia naturaliste n.sp., holotype male, 14.8 mm, U1–3, EP1–3, T, AM P69121, paratype female, 14.6 mm, G1–2, AM P69124, Bunker Bay, Cape Naturaliste, Western Australia. Scales for U1–3: 0.2 mm; G1–2: 0.3 mm; EP1–3: 0.5 mm; T: 0.1 mm.