Distribution of Leeches (Hirudinea) in the Benthic Communities of the Volga and Kama Reservoirs

The results of long-term studies of the diversity and quantitative development of leeches in the reservoirs of the Volga and Kama are presented. Eight species of leeches from 3 families Piscicolidae, Erpobdellidae and Glossiphoniidae were recorded, most of them are widespread freshwater species, representatives of the Ponto-Caspian (Archaeobdella esmonti) and Ponto-Azov (Caspiobdela fadejewi) complexes were also recorded. The share of leeches in the total biomass of “soft” benthos does not exceed 5.3%. It was noted that sandy soils are the most populated by leeches, the least – stony, clayey, heavily silted soils without plant residues. Mutual avoidance of species Archaeobdella esmonti – Erpobdella octoculata and Archaeobdella esmonti – Helobdella stagnalis was revealed, and two coenotic complexes of species of leeches and molluscs of Dreissena sp.: Helobdella stagnalis and Erpobdella octoculata with Dreissena polymorpha and Archaeobdella esmonti with Dreissena bugensis. The joint occurrence of leeches with different types of mollusks of Dreissena sp. is associated both with the conditions in which Dreissena lives and which it creates for consorts, and with interspecific interactions of benthic invertebrates included in the consortium.