Ezotinorchestia, Morino & Miyamoto, 2016

Genus Ezotinorchestia View in CoL gen. nov.

[New Japanese name: Kita-okatobimushi zoku]

Type species. Orchestia solifuga Iwasa, 1939 View in CoL .

Diagnosis. Body size medium. Eyes medium. Antenna 1 elongate, reaching mid-point of peduncular article 5 of antenna 2, peduncle subequal to flagellum in length, peduncular article 3 longer than either article 1 or 2. Antenna 2 in male not incrassate, flagellum subequal to peduncle in length. Upper lip lacking robust setae. Lacinia of left mandible 4-dentate. In maxilliped, outer margin of precoxa not stepped, palp articles 2 and 3 broad and mediodistally lobate, article 4 reduced.

Gnathopod 1 sexually dimorphic, male propodus deeply subchelate, carpus and propodus each with broad-based pellucid lobe, merus with small pellucid lobe, lateral surface of propodus with rows of submarginal and facial robust setae; in female, pellucid lobe or scabrous surface both absent, propodus palm vertical, shorter than dactylus. In gnathopod 2 of male, propodus powerfully subchelate, dactylus slightly attenuate; in female, mitten-shaped, basis weakly expanded anteroproximally, propodus with facial and submarginal setae on lateral surface. Pereopods cuspidactylate (bi-cuspate), locking robust setae of propodi reduced. Coxa of pereopod 4 as deep as wide. Posterior lobe of coxa of pereopod 6 smoothly curved. Pereopod 7 in male not sexually dimorphic. Coxal gills of pereopods 2 and 6 larger than those of pereopods 3–5, gill of pereopod 2 lobed, others convoluted, gill of pereopod 6 distally linguiform.

Pleonite side plates lacking marginal pits; pleopodal peduncles with 2 retinacula, arrays of robust setae both marginally and facially, and well-developed rami. Uropod 1 with distolateral robust seta of peduncle shorter than subdistal one; inner ramus with outer and dorsal marginal robust setae, outer ramus with marginal robust setae. Uropod 2 with rami subequal in length and marginal robust setae in 1 or 2 rows. Uropod 3 with peduncle slightly expanded; ramus stout, shorter than peduncle. Telson wider than long, with dorsolateral, distolateral, and distal robust setae, 6–12 setae in total per lobe.

Oostegites subovate, with numerous simple or slightly curve-tipped setae.

Etymology. The generic name is a combination of the ancient name for the region of Hokkaido, Ezoti, and part of the generic name Orchestia .

Remarks. There are three genera of terrestrial coastal talitrids in the northwest Pacific: Ezotinorchesita gen. nov., Kokuborchestia Morino and Miyamoto, 2015 , and Ditmorchestia Morino and Miyamoto, 2015 . They show several morphological similarities among themselves. Ezotinorchestia is close to Kokuborchestia in having 1) an elongate antenna 1, 2) a deeply subchelate and lobed merus-carpus in male gnathopod 1, 3) well-developed pleopods, 4) outer ramus of uropod 1 with robust setae marginally, 5) laterally to distally distributed robust setae on the telson, and 6) simple-tipped setae on the oostegites. However, Kokuborchestia displays: 1) a similar gnathopod 1 in both sexes, with a deep palm and lobed merus-carpus ( vs. sexually dimorphic), 2) the coxal gill of pereopod 6 being broad and distally truncate ( vs. distally linguiform), 3) densely setose (with plumose setae) peduncles of the pleopods ( vs. with robust setae), and 4) the telson lobe with 5–6 robust setae ( vs. 6–12). These are all regarded as generic difference. Ditmorchestia displays similarities to Ezotinorchestia in having: 1) a sexually dimorphic gnathopod 1, 2) a setose outer ramus of uropod 1(with robust setae), and 3) a setose telson lobe (also with robust setae). However, the shorter antenna 1, the produced basis of pereopod 7, the moderately reduced pleopods, and the robust ramus of uropod 3 in Ditmorchestia separate this genus from Ezotinorchestia .

Males of Orchestia Leach, 1814 , as redefined by Lowry and Fanini (2013), and Cryptorchestia Lowry and Fanini, 2013 , distributed mostly in the North Atlantic, show similar features to the present new genus in having: 1) a deeply subchelate gnathopod 1, 2) well developed pleopods, and 3) robust setae on the outer ramus of uropod 1. In addition, the lobed merus of gnathopod 1 is shared by Cryptorchestia and the present genus, while a high number of robust setae on telson (7+) is common to Orchestia and the present genus. However, both Orchestia and Cryptorchestia are separable from Ezotinorchestia by the shorter antenna 1, which does not exceed the end of peduncular article 4 of antenna 2. It should also be noted that recent molecular analyses of Orchestia and related species from the Mediterranean and northeast Atlantic suggest polyphyly of the genus Orchestia ( Pavesi et al. 2015) . Future molecular studies with extended species sampling could lead to further revision of the diagnosis of Orchestia .