Association of the parasitic and hyperparasitic epicaridean species (Crustacea: Isopoda) with the king crab Lithodes aequispinus Benedict, 1895 in the Bering Sea with description of Eremitione rybakovi sp. nov.

Abstract

The parasitic isopod suborder Epicaridea contains ∼800 species, all of which infest crustaceans. Until now only one species, Eremitione tuberculata (Richardson, 1904), occurring near the southern tip of South America, has been known from king crab hosts (Lithodidae). During two cruises of the Federal Institute of Fisheries and Oceanography (VNIRO) in 2020 and 2021, commercial king crab stocks in the western part of the Bering Sea were surveyed, including 37 juvenile specimens of the golden king crab, Lithodes aequispinus Benedict, 1895, sampled at depths of 236–450 m. Two thirds of them were infested with a species of Eremitione, new to science. Eremitione rybakovi sp. nov. morphologically closely resembles E. tuberculata, but differs in having a relatively shorter pleon in females (0.3–0.4 of total body length), a slightly distorted body (0–20°), and more developed subrectangular dorsal extensions on the pereopodal bases; males of the new species have a more slender antennule with six articles (five articles in E. tuberculata). Half of the brooding females of E. rybakovi sp. nov. were infested with the cabiropid hyperparasite Bourdonia cf. tridentata Rybakov, 1990, previously known from Bopyroides hippolytes (Kröyer, 1838). Aspects of the biology of L. aequispinus, that may be responsible for the high rates of parasite infestation, and relations within the “host–parasite–hyperparasite” system are discussed. DNA sequences are obtained from E. rybakovi sp. nov. and B. cf. tridentata for the COI and 18S rRNA genes, and the resulting phylogenetic placement of the new bopyrid species is shown.