Additional data on morphology and distribution of Melitoides valida (Shoemaker, 1955) (Amphipoda, Melitidae)

Abstract

The genus Melitoides Gurjanova, 1934 (Amphipoda, Melitidae) includes three species from the Arctic and northwestern Pacific: Melitoides makarovi Gurjanova, 1934, M. valida (Shoemaker, 1955), and M. kawaii Labay, 2014. M. makarovi and M. kawaii only were recorded until recently in the seas of the Russian Far East. Only two specimens of M. valida were found once near the Arctic coast of Alaska; therefore, the morphological description of the species was incomplete, which led to difficulties with its generic identification. For the first time, M. valida was found in the seas of the Russian Far East in September 2018 on the shelf of the Sea of Okhotsk, near the North-Eastern Sakhalin Island at the depth of 29 m on the sand bottom. Detailed re-description of the species was carried out using optical and electronic scanning microscopes by the Coleman protocol. The material collected is stored at the Crustacea collection of the Zoological Museum of Far Eastern Federal University (Vladivostok). The specimen from the Sea of Okhotsk is identical to the specimens of the type series from the Arctic coast of Alaska in the form of dorsal carination (with several teeth on posterior margin of pleon segments 2, 3 and urosomites 1, 2), in the structure of pereopods 1–7, especially in the form of propodus of pereopods 2 (palm with distinct posterior-distal tooth, as well as with three large and one small obtuse palmar teeth). M. valida description has been substantially supplemented, and information on its range has been expanded.