A new species of Thoracophelia (Annelida, Opheliidae) from the Yellow Sea of South Korea

BackgroundThoracophelia Ehlers, 1897 is a genus of Opheliidae characterised by the body dividedinto three distinct regions, modified parapodia in chaetiger 10 and a ventral grooverestricted to the posterior half of the body. To date, 18 species have been described in thegenus. Amongst them, six species have been recorded in northeast Asia.New informationA new species, Thoracophelia foliformis sp. nov., was discovered in the intertidal zone ofthe Yellow Sea, South Korea. This is the first Thoracophelia species report from theYellow Sea. This new species is closely related to T. dillonensis (Hartman, 1938) fromCalifornia and T. ezoensis Okuda, 1936 from Japan in having pectinate branchiae.However, the new species can be distinguished from the two species by the uniquecombination of the following characteristics: 15 pairs of wrinkled pectinate branchiae with12-15 filaments at best development and a foliaceous mid-ventral plate in the pygidium instead of one or two thick ventral cirri. Detailed descriptions and illustrations of T.foliformis sp. nov. are provided. Sequences of the mitochondrial cytochrome c oxidasesubunit I (COI), nuclear 18S ribosomal DNA (rDNA) and 28S rDNA of the new specieswere determined and analysed.