Abstract
The data on taxonomy and distribution of stagnicoline snails of the northern part of Western Siberia (Lower Ob' drainage basin) are relatively scant. The most recent survey of this group in the region was presented by Dolgin (2001) in his unpublishedthesis where three stagnicoline species are recorded: Lymnaea (Stagnicola) palustris (O.F. Miiller, 1774), L. (S.) terebra (Westerlund, 1885), and L. (S.) zebrella (B. Dybowski, 1913). Earlier authors published some data on stagnicolines of the northernwater bodies of Western Siberia (Westerlund 1887; Lindholm 1919; Khokhutkin 1966; Drozdov 1967; Dolgin & Johansen 1980; Dolgin & Novikova 1984), however, all those researchers, as well as Dolgin (2001), did not study the anatomical traits of the snails they had at their disposition and, thus, species identification was carried out solely on the basis of conchological characters. Meanwhile, conchological traits in stagnicoline snails are known to display a large extent of intra- and interspecific variation (Jackiewicz 1993), and therefore are not completely suitable for reliable species determination. In order to discriminate between numerous lymnaeid species, the study of shell characters should be accompanied by the examination of the structure of the reproductive organs. In some cases, it is utterly impossible to distinguish between certain stagnicoline species on the ground of conchological traits (Jackiewicz 1993).
NSTL