The ability to self-fertilization as a factor of eurybiontness in freshwater pulmonate mollusks

The reproduction parameters of eurybiontic ( Lymnaea stagnalis ) and stenobiontic ( Stagnicola corvus ) species originating from the reservoirs of Belarus and Russia with the different anthropogenic pollution are determined during experiment with cross-fertilization (CF) and self-fertilization (SF). There are the Chernobyl nuclear accident zone reservoirs, a warm effluent channel of a heat electric power station, the degrading ameliorative channel, the strongly polluted Svisloch River, non-contaminated Naroch Lake and a reservoir in the Angara river floodplain. L. stagnalis from non-contaminated reservoirs is characterized by high fecundity at the reproduction by SF and CF. With increase in the extent of reservoir pollution these parameters in L. stagnalis sharply decreased. S. corvus from the reservoir of the Chernobyl zone didn't breed at all through SF though its fecundity at CF far was rather high. Therefore S. corvus can exist only in reservoirs with rather stable environmental conditions, where their population density doesn't fall below some critical level. At the same time L. stagnalis population even at very low density can be restored by an single survived individual.