A new species of Wellsopsyllus (Copepoda, Harpacticoida, Paramesochridae) from the deep Southern Ocean and remarks on its biogeography

The new deep-sea copepod species of the family Paramesochridae (Copepoda, Harpacticoida) presented here was collected during the scientific ANtarctic benthic DEEP-sea biodiversity cruise II (ANDEEP II) to the Weddell Abyssal Plain and western Weddell Sea and the CROZet natural iron bloom and EXport experiment (CROZEX cruise) to the Crozet Isles in the Indian Ocean. The new species has been allocated to the subgenus Wellsopsyllus within the genus Wellsopsyllus Kunz, 1981, based on the 1-segmented endopods and 3-segmented exopods of swimming legs 2–4. Furthermore, the new species shows a 1-segmented exopod of the antenna. Wellsopsyllus (W.) antarcticus sp. n. can be distinguished from its congeners by its small body size, the presence of two setae on the distal segment of the endopod of the first swimming leg, by the very small furcal rami, the extremely reduced endopods of second and third swimming legs, the reduced mandibular palp and maxillula, as well as by the size and armature of the fifth and sixth swimming legs in both sexes. Difficulties of the placement of the new species into a suitable genus show an insufficiency in the present family classification. In the future, a revision of the genus Wellsopsyllus is essential. With its presence in the western Weddell Sea and the Indian Ocean, the new species may have a wide distribution range. Furthermore, it is the first abyssal species of the genus Wellsopsyllus sampled outside of the Scotia Sea.