A review of current knowledge of the Harpacticoida (Copepoda) fauna diversity in ancient Lake Baikal

We provide an overview of available knowledge on the Lake Baikal harpacticoid copepod fauna. The Harpacticoida is the third most species-rich group of crustaceans in Lake Baikal. They are abundant and are represented on all bottom biotopes. Although the species composition had been relatively stable and there were general assumptions about the origin of the Baikalian endemic fauna and the reasons for its immiscibility with the Siberian fauna, the application of molecular methods to their study has resulted in new insights. These include newly discovered species, species formerly classified as endemics being shown to be widespread in the Palearctic, and single species found to be probable species complexes. The research priorities identified at the beginning of the 21st century by Okuneva & Evstigneeva (2001) remain relevant: 1) re-describing most species and establishing type material in museum collections, 2) undertaking a complete revision of the Baikalian Canthocamptidae, 3) studying the behavior and biology of species, 4) using molecular sequence data to explore their evolutionary history.