The locations of Boreoelona contortrix in the waterbodies of Western Siberia and Kazakhstan are reported as well as the data on morphology of shells and copulatory apparatus of the species from different parts of its range. The interpopulation variation is considered. On the basis of anatomical and morphometric study, it has been shown that there are no statistically significant differences between males and females of B. contortrix. Problems of taxonomy of the Boreoelona species are discussed.

On the basis of dissections and shell measurements we studied sexual dimorphism in shell shape in Parafossarulus manchouricus taken from the bay of the Bira River (Russian Far East). It is shown that there are no statistically significant differences in shells of males and females in P. manchouricus .

This review deals with the problem of mollusk invasions into the inland waters of the Western Siberian region. The data on all the alien species of snails and bivalves registered up to now in water bodies of the region are provided. Possible ways and mechanisms of penetration of the alien species into the Western Siberian water bodies are discussed. The most well-studied case of mollusk invasion, that of the European river snail, Viviparus viviparus (L., 1758), into water bodies of the Ob-Irtysh basin, is considered in detail. An ecological and geographical classification of the invader species is proposed. It includes three categories: (1) exotic species, (2) species belonging to the boreal European complex which regain the lost part of their range, and (3) heat-loving species of South European origin. We hypothesize that, in the foreseeable future, the inflow of the alien mollusk species to the Western Siberian inland waters will remain low owing to some physical-geographical peculiarities of this area.

The data on distribution of molluscs of the genus Digyrcidum Locard, 1882 in waterbodies of the Urals and Western Siberia are given. A new species, Digyrcidum starobogatovi Andreeva et Lazutkina, sp. nov., is described. This species inhabits waterbodies of the Urals and Western Siberia sympatrically with the species Digyrcidum bouguirgnati (Paladilhe, 1869).

The patterns of spatial variation in gastropod diversity in the waterbodies of western Siberia have been revealed. The highest species and generic diversity of freshwater gastropods is found in the waterbodies of the forest-steppe zone; from there, these parameters significantly decrease northwards, reaching their minimum beyond the polar circle. The proportion of gastropods of non-European origin increases in the same direction. The possible reasons for these changes in the spatial diversity of aquatic gastropods and the likely connections between the latitudinal variation of their diversity and the geological history and features of the relief of western Siberia are discussed. It is assumed that the forest-steppe zone of western Siberia is a local center of aquatic gastropod diversity.

The South-European species of snails Digyrcidum bourguingati is for the first time found in the waterbodies of the Urals and Western Siberia. Its description is given as well as the data on its geographical distribution and morphology. The paper is illustrated by photos of shell and the penis.

The results of long-term (19732005) authors studies of the inland water gastropod of Western Siberia are given.Following to the most recent taxonomic surveys (Starobogatov et al., 2004;Kantor, Sysoev, 2005), we count 134 gastropod species belonging to nine families to dwell in the region under discussion.Most of them (86 out of 134) are pulmonates.The most diverse fauna of water snails was found in the Irtyshian zoogeographical province, and the least diverse in the Lower Obian one.There is a clear latitudinal gradient of gastropod species richness in Western Siberia.Differences in species composition between zoogeographical provinces as well as possible pathways of snails migration through Western Siberia are discussed.It was found, the gastropod fauna of Western Siberia inland waters has a European origin with a participation of autochtonous species and migrants from Eastern Siberia and Northern America.