A new species of Paradulichia (Amphipoda: Senticaudata: Dulichiidae) collected from hadal depths of the Kuril-Kamchatka Trench

A new species of the amphipod genus Paradulichia Boeck represents the fourth known species of the genus. The specimen was collected from the hadal depths of the southernmost Kuril-Kamchatka Trench during the KH-22-8 expedition of the Research Vessel (R/V) Hakuho-Maru, making this the deepest species of Paradulichia described. The newly described species is distinguished from its congeners by an expanded gnathopod 2 that is dissimilar to gnathopod 1, and coxal gills at the base of pereopods 3–5, traits not previously observed in Paradulichia. Despite these differences, the species possesses generic characters: fused urosomes 2 and 3, with vestigial and single articulate uropod 2. Consequently, the new species was placed in the genus, and the genus diagnosis was amended to accommodate apomorphic gnathopod 2 and coxal gills. Additionally, partial nucleotide sequences of mitochondrial genes for cytochrome c oxidase I (COI) and 16S ribosomal RNA were determined. In the maximum likelihood tree based on the COI sequences, Paradulichia atsushii sp. n. formed a highly supported clade with some MOTUs (Molecular Operational Taxonomic Units) obtained from the Kuril-Kamchatka Trench during the German/Russian KuramBio II expedition. A preliminary key to the world species of Paradulichia is also provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:76CEF68B-017B-4BEC-883D-E2689A766CFB