Three new species of the family Idyanthidae (Copepoda, Harpacticoida) from sublittoral zones around the Korean Peninsula

There are few taxonomic studies of the harpacticoid family Idyanthidae Lang, 1944 in the Pacific Ocean. As a first report of the family in this region, one species of the monotypic genus <i>Idyellopsis</i> Lang, 1948 and two species of the genus <i>Idyella</i> Sars, 1905 are described from sublittoral habitats around the Korean Peninsula. <i>Idyellopsis orientalis</i> sp. nov. is distinguished from the type and only species of the genus, <i>Idyellopsis typica</i> Lang, 1948, in the length:width ratio of the body and genital double-somite, length of caudal seta I, and structure of the female P5 baseoendopod. <i>Idyella dolichi</i> sp. nov. and <i>Idyella exochos</i> sp. nov. share the armature of the female P5 exopod with four setae with <i>Idyella exigua</i> Sars, 1905, <i>Idyella major</i> Sars, 1920, and <i>Idyella pallidula</i> Sars, 1905. However, the two new species differ from the three European species in the armature of the terminal segment of the P1 endopod and female P5 baseoendopod, and in the shape of the genital double-somite. The male of <i>Idyella dolichi</i> sp. nov. also has two distinct features: the distal two segments of the P2 endopod are completely fused, and the third segment of the antennule has a prominent outer projection. The geographical distribution of <i>Idyellopsis</i> and <i>Idyella</i> is extended by the discovery of three new species in Korean waters. We also discuss a possible phylogenetic relationship among members of family Idyanthidae at genus level.