Copepods of the genera Haplostomella and Haplostomides (Cyclopoida: Ascidicolidae) associated with ascidians from the White Sea and Russian Far East coastal waters

A new species of Haplostomella Chatton & Harant, 1924, H. borealis n. sp., is described from two ascidian hosts taken in the White Sea. This species is most readily distinguished from its congeners by the structure of the mandible which comprises a strong tapering gnathobase and a vestigial palp. Supplementary descriptive notes are provided on Haplostomella distincta Ooishi & IlIg, 1977, based on new material discovered on the opposite side of the Bering Strait from the original material. Minor geographical variation is exhibited by this species. A new species of the genus Haplostomides Chatton & Harant, 1924, H. sanamyani n. sp., is also described, based on material collected in the Bering Sea. A key to species is provided to facilitate the identification of the nine species recognised in this genus.