Investigation of Shell Characteristics in Chondrula tridents (Pulmonata, Enidae) from Highland and Plain Habitats of the Forest–Steppe of the Volga River Basin

Abstract

Variability of the shell size characteristics was studied in the terrestrial mollusk Chondrula tridens (Muller, 1774) from highland and plain habitats in the forest–steppe of the Volga River basin. The shell height (SH) and width (SW), the height and width of the mouth, and the SH/SW ratio mostly contribute to the species variability. The SH/SW ratio reflects the species–specific constitution of the shell. Analysis of the elementary features and proportions, as well as of the mouth armament of shell structures, indicates significant heterogeneity of the species. The presence of scarps and rock outcrops in some regions studied explain large sizes of snail shells. The decrease in SH, increase in the roundness of shells, and better development of the mouth teeth in mollusks inhabiting the chalk steppe of the southern forest–steppe reflect their adaptation to more xerothermic conditions.