Polychaete composition from the abyssal plain adjacent to the Kuril–Kamchatka Trench with the description of a new species of Sphaerephesia (Polychaeta: Sphaerodoridae)

During the KuramBio expedition, the abyssal plain adjacent to the Kuril–Kamchatka Trench was sampled in July–August 2012. More than 5200 individuals of Polychaeta belonging to 38 families, 108 genera and about 144 species were found. Six genera have been reported for the Northwest Pacific for the first time. About 50% of the collected polychaete species are considered as new to science. One of these, Sphaerephesia lesliae sp. n., is described herein. The detailed description of the new species is presented and its differences from similar species are shown. This eighth species of the genus is characterized by the presence of macrotubercles with two paired terminal papillae. The genus Sphaerephesia Fauchald, 1972 is newly recorded in the Northwest Pacific. An updated key to the species of the genus Sphaerephesia is provided.