Morphological properties of the granules of the screening pigment in the retinae of camera eyes of gastropod mollusks with different light preferences were studied. It was demonstrated that the pigment granules of mollusks can differ by color and size but do not differ by structure, electron density and form. Light conditions of mollusks’ habitats can influence on the amount of the screening pigment, which in its turn does not affect resolving ability of the eyes.

The population structure of the terrestrial mollusc Brephulopsis cylindrica (Gastropoda, Pulmonata, Enidae) in the native area (Crimea Peninsula) and out of its borders (two adventive groups in the city of Belgorod) was studied on the basis of conchometric characteristics and analysis of polymorphic allozyme loci. For all the morphometric parameters statistically significant differences were found between the studied groups. In all studied populations a high level of intrapopulation genetic variability was revealed (Fit = 0,401). At the same time, the considerable variability of the conchological parameters and the high level of allelic polymorphism at a number of loci identified in adventitious colonies create the prerequisites for successful adaptation to new conditions and further expansion of the species range in urbanized areas. 

In 2015-2016 land molluscs from 48 natural and anthropogenically transformed localities in Syunik Region of Armenia were investigated. The analysis of our and literature data gave the possibility to draw up a species list of land molluscs of Syunik Region, which includes 78 species. Two forms with unclear taxonomic status are described: Stenomphalia sp. and Chondrula cf. sunzhica.

On the basis of dissections and shell measurements we studied sexual dimorphism in shell shape in Parafossarulus manchouricus (Gerstfeldt in Bourquignat, 1860) 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.