The Taz River basin (TRB) is a large aquatic system in the north of Western Siberia (WS). Information on the bivalves of this basin is scarce and published almost exclusively in Russian. This study aims at giving an overview of the freshwater bivalve fauna of the TRB. Malacological collections of the Zoological Institute (RAS) and the Institute of Plant and Animal Ecology (Ural Branch, RAS), critical review of the scientific literature, and own samples made in TRB were the basis of this work. MolluscaBase (http://www.molluscabase.org/) nomenclature and taxonomy were followed. In total, 26 species of 6 genera from 2 families were identified. The Unionidae was represented by a single species. All other species belong to the genera Sphaerium (5 species), Musculium (1), Pisidium (2), Odhneripisidium (2), and Euglesa (15) of the Sphaeriidae. The greatest species richness and abundance were noted for the genus Euglesa – 15 species and 51.9% of the total number of specimens in the collection. Nine species accounted for more than 80% of the collection. Other species are represented by a much smaller number of specimens. Zoogeographically the core of the fauna is formed by widespread Holarctic and Palaearctic species – 69.2%; European-Siberian and European-Central Asian species composed 30.8%. No invasive species has been encountered. Observed species richness of bivalves in the TRB is more than 80% of all in WS (Babushkin, 2020 a, b), which corresponds to world concepts (Bogan, 2008; Lopez-Lima et al., 2018; Bolotov et al., 2020). In the south of WS, both gastropods and bivalve invasive species were recorded (Vinarski et al., 2015; Babushkin et al., 2021), whose northward spread is very likely explained by the current climate changes. To protect the natural aquatic ecosystems of the TRB, it is necessary to organize ecological monitoring, scientific investigations, and habitats conservation.
Keywords: Taz River basin, Malacofauna, Unionidae, Sphaeriidae, Species Richness.
Acknowledgments: The fieldwork, literature review, and examination of museum collections (partially) were supported by the Russian Foundation for Basic Research (project 19-04-00270), Russian Foundation for Basic Research, and Tyumen Region (project 20-44-720008), and the Department of Education and Youth Policy of the Khanty-Mansiysk Autonomous Okrug–Yugra. A significant part of the work on the examination of museum collections was supported by the Russian Science Foundation (project 19-14-00066).