INVESTIGATION OF SHELL CHARACTERISTICS IN CHONDRULA TRIDENS (PULMONATA, ENIDAE) FROM HIGHLAND AND PLAIN HABITATS OF THE FOREST-STEPPE VOLGA RIVER BASIN

摘要

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