Two New Species of the Genus Melita (Crustacea : Amphipoda) from Shallow Waters of the Seto Inland Sea of Japan

TLDR: The two new species markedly differ from other species of Melita previously reported from the same region in the morphology of the male gnathopod 1 and the female coxa 6, and the biarticulate uropod 3 which will be discussed from a taxonomic point of view.

Abstract: Two new species of gammaridean amphipods of the genus Melita, M. hoshinoi and M. quadridentata, are described from shallow waters of the Seto Inland Sea of Japan. Melita hoshinoi is unique within the genus in having two basofacial spines on the peduncle of uropod 1. Melita quadri­ dentata is characterized by markedly setose pereopods 6-7 and uropod 3. The two new species are clearly distinguishable from other congeners also by the shapes of male gnathopod 1 and female coxa 6. A biarticulate outer ramus of the uropod 3, which is usually regarded as an important characteristic of the genus Abludomelita (sensu Karaman, 1981) that distinguishes it from the genus Melita, is rec­ ognized in the two new species. The present paper deals with two new species of the genus Melita Leach (Gam­ maridea, Melitidae) from the Seto Inland Sea of Japan. Although the materials of these two new species used for the present study were obtained only from a small area around the Mukaishima Marine Biological Station, they are not rare species. Actually they are very abundant there and have repeatedly been collected. The two new species markedly differ from other species of Melita previously reported from the same region (Yamato, 1987, 1988) in the morphology of the male gnathopod 1 and the female coxa 6, and the biarticulate uropod 3 which will be discussed from a taxonomic point of view. The new species seem to differ from the previously report­ ed species also in the habitat because they have so far been found in subtidal sedi­ ments, while the latter species are known to occur in intertidal and brackish-water areas. The figures of appendages are depicted from two specimens, which are the holotype and the allotype. The figures from subsidiary specimens are denoted after the dash, like "m2" and "f2". Type specimens will be deposited in the National Science Museum, Tokyo, after the completion of this study. Abbreviations used in the figures. R., right; L., left; A, antenna; CX, coxa; E, epimeral plate; G, gnathopod; H, head; IP, inner plate; LL, lower lip; MD, mandible; MX, maxilla; MXP, maxil­ liped; OP, outer plate; PL, pleopod; PLS, pleosomite; PR, pereopod; T, telson; U, uropod; UL, upper lip; URS, urosomite; f, female; i, inner surface; o, outer surface.