Deep-sea amphipod genus Eurythenes from Japan, with a description of a new Eurythenes species from off Hokkaido (Crustacea: Amphipoda: Lysianassoidea)
Two species of the giant deep-sea amphipod genus Eurythenes are reported from two bathyal habitats in Japanese waters based on a morphological examination and DNA analyses. The new species E. aequilatus collected off Hokkaido in the Sea of Okhotsk comprises a distinctive lineage within the known Eurythenes species and genetic groups. This finding sheds light onto the overlooked role of the marginal deep sea in the species diversification history of Eurythenes. Eurythenes specimens collected from the south off Okinawa Island in the Philippine Sea were identified as E. magellanicus, confirming the presence of a population in the western North Pacific. Past and present trans-oceanic dispersal of this species is briefly discussed based on the mitochondrial DNA sequences obtained from the Okinawa specimens of E. magellanicus.