Anthessius antarcticus n. sp. (Copepoda: Poecilostomatoida: Anthessiidae) from antarcticwaters living in association with charcotia granulosa (Mollusca: Nudibranchia: Charcotiidae)

Abstract

A new species of the genus Anthessius Della Valle, 1880 is described under the name A. antarcticus. It is ectosymbiont of the nudibranch Charcotia granulosa Vayssière, 1906 from the South Shetland Islands in the Southern Ocean. The female of the new species is distinguished from its congeners by the following combination of diagnostic morphological characters: 1) antenna with two terminal claws; 2) mandible with a seta between distal and outer lashes; 3) third exopodal segment of leg 4 with four spines and five setae (formula: III, I, 5); and 4) caudal ramus 2.40 times as long as wide. Its relationship with its congeners and other anthessiid genera are discussed. This is the first species of the genus found to be related to a nudibranch, and remarkably, it is also the only record of Anthessiidae from Antarctica.