First record of the family Calliopiidae (Crustacea, Malacostraca, Amphipoda) from Korean waters, with description of new species Calliopius ulleungensis sp. nov.

A new species of the family Calliopiidae was collected from the East Sea of Korea. <i>Calliopiusulleungensis</i> <b>sp. nov.</b> is similar to <i>C.columbianus</i> Bousfield & Hendrycks, 1997 in having numerous calceoli on the posteromedial margins of antennae and a weakly carinate body. However, the new species can be distinguished from <i>C.columbianus</i> by the shorter process on peduncular article 3 of antenna 1, subrectangular eyes, and fewer articles in the antenna flagellum. This species, along with <i>C.ezoensis</i>Shimoji et al. 2020, occurs in the Western Pacific. The females of the two species are morphologically very similar, but the males of <i>C.ezoensis</i> are easily distinguishable, as the gnathopod 1 is larger than gnathopod 2. The new species is fully illustrated and extensively compared with related species. In this paper, both <i>Calliopius</i> and Calliopiidae are reported from Korea for the first time. A key to species of <i>Calliopius</i> is also provided.