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.