Life cycle of Valvata cristata O. F. Müller, 1774 (Gastropoda: Heterobranchia) in the laboratory

Abstract

Laboratory studies in 1991-2001, supplemented with observations in natural habitat, made it possible to establish the following characteristics of the life cycle of Valvata cristata O. F. Müll.: female maturity at shell diameter of 2.05-2.95 mm, number of whorls 2.375-3, 55-533 days from hatching, depending mainly on food conditions. Mean life span in good food conditions 377 days, in bad food conditions 896 days (maximum 1,170 days). Snails kept in pairs deposited a mean number of 51 cocoons per lifetime (maximum 105), with a total of 134 eggs (maximum 353); the number of eggs per cocoon ranged from 0 to 10, rarely more than 16 (mean 2.6). Depending on life span there were 1-3 reproductive seasons. Of 20 adult snails kept singly, only one laid eggs which hatched. The mean maximum shell size for snails kept in pairs: 3.28 mm, 3.125 whorls, for snails kept singly: 3.93 mm, 3.375 whorls (maximum 4.70 mm, 3.750 whorls). Snails with shells of strongly descending whorls were almost always infected with trematode larvae located in their gonads. Snails infected when young never reached female maturity.