Significance of Cross-Fertilization and Self-Fertilization for Preserving the Population Stability of Dominant ( Lymnaea stagnalis ) and Rare ( Stagnicola corvus ) Species of Freshwater Pulmonary Mollusks

— The growth and reproduction parameters in offspring of abundant ( Lymnaea stagnalis ) and rare ( Stagnicola corvus ) pulmonate species originating from the specimens captured in water bodies with different forms and levels of anthropogenic contamination are determined in a reproduction experiment by cross-fertilization (CF) and self-fertilization (SF). It is shown that SF leads to an increase of pre-reproductive age, a decline in fecundity, and a decreasing amount of breeding individuals and growth rate of population numbers. An increase in the contamination level of water bodies leads to a decrease in the ability to SF in L. stagnalis. Compared to this species, S. corvus is characterized by a reduced ability to SF. It could be one of the most crucial reasons for the low abundance of S. corvus in nature.