Description of a New Talitrid Genus, Ezotinorchestia with a Redescription of E. solifuga (Iwasa, 1939) comb. nov. (Crustacea: Amphipoda: Talitridae) Author Morino, Hiroshi Department of Zoology, National Museum of Nature and Science, 4 - 1 - 1 Amakubo, Tsukuba, Ibaraki 305 - 0005, Japan E-mail: morino 631 @ gmail. com & Corresponding author morino631@gmail.com Author Miyamoto, Hisashi 4 - 9 Kasumi, Maruoka-cho, Fukui 910 - 0231, Japan E-mail: dream _ 50000000690737 @ yahoo. co. jp dream_50000000690737@yahoo.co.jp text Species Diversity 2016 2016-05-25 21 1 65 70 http://dx.doi.org/10.12782/sd.21.1.065 journal article 7120 10.12782/sd.21.1.065 cdc7d13c-1741-4970-9b3e-0d2e25ed4ec8 2189-7301 4585037 4FE2AA1E-C38B-4919-82C2-FEAD415FDEA9 Genus Ezotinorchestia gen. nov. [New Japanese name: Kita-okatobimushi zoku] Type species. Orchestia solifuga Iwasa, 1939 . 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 . Fig. 1. Ezotinorchestia solifuga ( Iwasa, 1939 ) . Male, 12.9mm (NSMT-Cr 24220), Utoro, Abashiri, Hokkaido, Japan. A, habitus, lateral view (after Morino 2015); B, antenna 1; C, upper lip; D, lower lip. Scale 1, 1.0 mm for A; scale 2, 0.2mm for C and D; scale 3, 1.0 mm for B. 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 .