Records of Boeckella poppei (Mrazek, 1901) (Calanoida: Centropagidae) obtained during Ukrainian Antarctic Expeditions

The copepod Boeckella poppei (Mrazek, 1901) (Calanoida: Centropagidae) is one of the Maritime Antarctic’s most common freshwater zooplankton species. It was first reported from the Antarctic in 1961–1962 on Signy Island (South Orkney Islands). Although the in situ refugia hypothesis suggests that this species survived in regional refuges throughout multiple Pleistocene glacial cycles. Since then, its presence has been confirmed from many locations in the Maritime Antarctic. The species is also present on sub-Antarctic South Georgia and in lakes around the Prince Charles Mountains in Continental Antarctica, and in southern South America. However, in the central part of the western Antarctic Peninsula, specifically in the Wilhelm Archipelago, there have to date been only a few disjointed records of the species and its distribution here has not been documented in any detail beyond being noted as numerous both north and south of the Ukrainian Antarctic Akademik Vernadsky station. Here, we report B. poppei in 51 samples obtained from 23 lakes on eight islands in the Wilhelm Archipelago. Living specimens were observed both in the ice-free summer season and well after the formation of surface ice on water bodies. Adult specimens were present in all samples, while the copepodid stages were only rarely observed and nauplii were not encountered.