Talorchestia anakao, 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 : 369-371

Talorchestia anakao sp. nov.

(Fig. 13)

Talorchestia martensii .― Ledoyer, 1968: 279, pls 20–21.― Ledoyer, 1986: 1017, fig. 402.

Type material. Holotype, male, 11 mm, MNHN-IU-2008-23655, Plage Est , Nosy Vé, Madagascar (~ 20°39’S 43°36’E), zone des laisses de vives-eaux, coll., B. Thomassin, Station 862 . Paratype: 1 female, 9 mm, MNHN-IU- 2008-23656, same locality as holotype .

Additional material. About 30 specimens, MNHN-IU-2013-14902, same station as type material. Many specimens, collected by Michel Pichon and identified as T. martensii by Ledoyer, from beach at Tuléar, Madagascar, are not in the MNHN collection .

Type locality. Plage Est , Nosy Vé, Madagascar (~ 20°39’S 43°36’E) .

Habitat. Supralittoral sand beach.

Etymology. Named for Anakao, the small village near Nosy Vé.

Description. Male, based on Ledoyer 1968: 279, pls 20–21.

Head. Antenna 2 peduncular articles without marginal row of robust setae, with many small robust setae, article 5 longer than article 4. Maxilla 1 with small palp, 1-articulate.

Pereon. Gnathopod 1 sexually dimorphic; parachelate; coxa smaller than coxa 2; carpus longer than propodus, 1.8 × as long as propodus, 2.4 × as long as broad; propodus subrectangular, anterior margin with 5 groups of robust setae, 1.8 × as long as broad, palm acute; dactylus longer than palm, without anterodistal denticular patch. Gnathopod 2 sexually dimorphic; subchelate; basis slender; ischium with weak rounded lobe on mid-anterior margin, without anterodistal lobe on medial surface; carpus triangular, reduced (enclosed by merus and propodus), posterior lobe absent, not projecting between merus and propodus; propodus subovate, 1.5 × as long as wide, palm reaching about 40% along posterior margin, palm smooth, without protuberance or shelf near dactylar hinge, lined with robust setae, with small proximal sinus, posteroproximal corner without spine; dactylus subequal in length to palm, curved, without anteroproximal bump, posterior margin lined with small robust setae distally, with posteroproximal sinus and small projection. Pereopods 2–4 coxae wider than deep or as wide as deep. Pereopod 3 dactylus without anterodistal patch. Pereopod 5 propodus distinctly longer than carpus; dactylus without anterodistal setal patch. Pereopods 6–7 not sexually dimorphic. Pereopod 6 coxa posterior lobe inner view posteroventral corner rounded, posterior margin perpendicular to ventral margin, posterior lobe with ridge, posterior lobe with 4 marginal setae. Pereopod 7 basis lateral sulcus present, slightly pronounced, posterodistal lobe absent; distal articles (merus and carpus) slender; merus posterior margin straight.

Pleon. Pleopods 1–3 biramous. Epimeron 2 subequal in length to epimeron 3. Epimeron 3 posterior margin smooth, with minute setae, posteroventral corner with large subacute tooth. Uropod 1 peduncle with 17+ robust setae, distolateral robust seta small (less than 1/4 length of exopod); endopod with 10 marginal robust setae in two rows; exopod without marginal robust setae. Uropod 2 peduncle with 5 robust setae; endopod subequal in length to exopod, with about 8 marginal robust setae in two rows; exopod with 2 marginal robust setae. Uropod 3 peduncle with 7 robust setae; ramus partially fused to peduncle, 3.1 × as long as broad, linear, with about 3 marginal robust setae, with 4–5 apical robust setae. Telson dorsal midline entire, 7–8 setae per lobe.

Female (sexually dimorphic characters). Female based on Ledoyer 1968: 279, pls 20–21. Gnathopod 1 simple; carpus about 2.0 × as long as propodus, 3.0 × as long as broad; propodus anterior margin with 6 groups of robust setae. Gnathopod 2 mitten-shaped; basis expanded anteromedially; 1.9 × as long as wide, lined with robust setae.

Remarks. Talorchestia anakao is the southernmost species of Talorchestia along the east African coast. It belongs to the species group without a proximal protuberance on the palm of male gnathopod 2. Within this group it has a large subacute posteroventral tooth on epimeron 3, similar to Talorchestia sp. from north-eastern India, T. dampieri from north-western Australia, T. gracilis from the South China Sea and T. affinis from north-eastern Africa and the Red Sea. Talorchestia anakao has the shortest palm in this group, reaching about 40% along the posterior margin of the propodus (47% in T. sp., 56% in T. dampieri and 50% in T. affinis ). In T. anakao the dactylus of male gnathopod 2 is only as long as the palm whereas in its nearest geographic neighbour, T. affinis , the dactylus is longer than the palm

Distribution. Madagascar. Nosy Vé ( Ledoyer 1968, 1986).