Taxonomy of the genus Elasmopus (Crustacea, Amphipoda) in Japan and South Korea, with description of a new species

To advance the limited understanding of the East Asian Elasmopus fauna, field surveys were conducted in Japan and South Korea. In the present study, a new species, E. lumbiniger sp. nov., is described. The new species is distinguished from its congeners by a strongly projected posteroventral corner of the epimeral plate 3, long slender setae on the anterodistal corner of the male gnathopod 2 carpus, a mid-palmar ridge on the male gnathopod 2 propodus, and a smooth posterior margin on the basis of pereopods 5–7.

In addition, E. koreanus is recorded in Japan for the first time, and the known distribution range of E. mukuinu has been significantly extended. The nucleotide sequences of the mitochondrial cytochrome c oxidase subunit I (COI) of these species were determined, and the genetic distances among Elasmopus species were provided. A key to the species of Elasmopus found in East Asia is also provided.