Integrative taxonomy of Zeuxo (Crustacea: Peracarida: Tanaidacea) from Japan, with the description of a new species

We describe a new tanaidid species, Zeuxo molybi sp. n., from Kominato, Chiba, Japan. Zeuxo molybi closely resembles the Japanese congener Zeuxo ezoensis, but differs in having (1) the pereopod-1 carpus without dorsodistal spiniform setae; (2) two or three ventrodistal simple setae on the pereopod-1 propodus in females, and three or four in males; and (3) the pereopod-6 propodus with four or five flattened denticulate setae. The two species also differ in the pattern of dorsal pigmentation on the carapace. Kimura 2-parameter distances between the two species were 15.6-16.9% for the cytochrome c oxidase subunit I (COI) gene and 2.8% for the 18S rRNA gene; the former value is much greater than intraspecific distances previously reported for Z. ezoensis (0-1.5%), confirming our conclusion from morphology that Z. molybi and Z. ezoensis are not conspecific. In a COI-based maximum-likelihood phylogenetic tree, the Japanese taxa Z. molybi, Z. ezoensis, and Z. cf. normani did not form a clade.

Automated summary

We described a new tanaidid species, Zeuxo molybi, from Japan, which closely resembles but differs from its congeners. The two species have differences in morphology, leg structure, and dorsal pigmentation. Genetic analysis confirmed that they are not conspecific.