Opisa

Narahara-Nakano, Yukiko, Kakui, Keiichi & Tomikawa, Ko, 2016, Opisa takafuminakanoi, a new species of Opisidae from Hokkaido, Japan (Crustacea: Amphipoda), Zootaxa 4200 (2), pp. 335-339 : 338

Key to the species of Opisa modified from Bousfield (1987)

1 Posterior margin of epimeral plate 3 crenulated or denticulated; outer plate of maxilliped almost reaching distal margin of palp article 3 ............................................................................................................................................................................ O. tridentata

- Posterior margin of epimeral plate 3 smooth; outer plate of maxilliped not reaching distal margin of palp article 3........... ........... 2

2 Dactylus of gnathopod 1 short, nearly straight, posterior margin dentate; palm of propodus of gnathopod 1 straight, lined with close-set “palisade” robust setae; rami of uropod 3 without marginal setae............................................................... O. odontochela

- Dactylus of gnathopod 1 large, strongly curved, posterior margin smooth; palm of propodus of gnathopod 1 concave, with few slender setae.......................................................................................................................................................................................3

3 Lacinia mobilis of left mandible developed; posterior lobe of coxa 5 weakly developed; inner ramus of uropod 2 with robust setae ......................................................................................................................................................................................... O. eschrichti

- Lacinia mobilis of left mandible vestigial; posterior lobe of coxa 5 well developed; inner ramus of uropod 2 without robust setae ................................................................................................................................................................ O. takafuminakanoi sp. nov.