A survey of cercariae and metacercariae (Trematoda, Digenea) from bithyniid snails (Gastropoda: Bithyniidae) in lake-river systems in Northern Kulunda (of the steppe zone of the West Siberia Plain) is presented. The role of Bithynia tentaculata (Linne, 1758) and Bithynia troscheli (Paasch, 1842) as the first intermediate hosts and as the second intermediate hosts of trematodes in the study area was accomplished for the first time. Twelve species of cercariae (8 families) and 12 species of

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... rcariae (6 families) were found in bithyniid snails. Altogether, bithyniid snails were infected with 23 trematode species including 16 genera in 11 families. New Cercariae Holostephanus sp. and five original species of trematode metacercariae, were discovered in bithyniid snails of the steppe zone of the West Siberia Plain. The dominant cercariae were those of the families Prosthogonimidae and Lecithodendriidae. The most prevalent metacercariae were Echinoparyphium aconiatum Dietz, 1909 and E. recurvatum Linstow, 1873 (both family Echinostomatidae) and Cyathocotyle bithyniae Sudarikov, 1974 (Cyathocotylidae). B. troscheli infected by trematode parthenitae of Holostephanus sp. was detected in the Russia for the first time.