Poster (download) Alena Yakhnenko1, Valeria Itskovich21LIN SB RAS, Irkutsk, Russia JINR, Dubna, Russia, yakhnenkoas@gmail.com2LIN SB RAS, Irkutsk, Russia, itskovich@mail.ru Freshwater sponges play an important role as filtrators in lake ecosystems. Endemic Baikal sponges make up the bulk of the lake benthos biomass. Events of mass diseases and death of sponges occur on Lake Baikal for the last decade. Due to high morphological plasticity, there is a lack of clear criteria for the species identification of Baikal sponges. However, the development of such criteria is very important for population structure studying purposes and determination of the recoverability of populations.В  In this work, we first assessed the suitability of the 5\’-terminal fragment and the I3M11 fragment of the COI gene for population studies of endemic Baikal sponges, and also examined alternative markers for such studies. It is shown that in the Lubomirskia baikalensis samples, collected in different basins of Lake Baikal, only two different haplotypes were found, which indicates the unsuitability of this fragment for population studies. As an alternative, we propose to use microsatellite markers, which have successfully shown themselves both in studying the structure of populations of marine and freshwater sponges. Currently, work is underway to study the population structure of Baikal endemic sponges using microsatellite markers.