Size structure, age, mortality and fecundity in Viviparus viviparus (Linnaeus, 1758) (Gastropoda: Architaenioglossa: Viviparidae)

Abstract

Field and laboratory experiments were aimed at establishing the relationship between growth rate, age, mortality and fecundity of Viviparus viviparus (L.). Fecundity was found to depend on the female's size. The size (shell dimensions) did not affect the size of newborn snails; females of different size classes produced offspring of the same shell height (4.0 mm) and width (4.5 mm). In the first year of the experiment growth rate was higher in the field than in the laboratory. Sex could be recognised and developing embryos could be found in females in the middle of the second year of the experiment. Juvenile V. viviparus appeared in the laboratory when the females were 18 months old and had achieved size class III. Their shell increments were uniformly distributed, without visible dark winter rings or rings of summer growth inhibition. Winter and summer rings appeared in the second year in the field culture; the second winter ring appeared in the third year of field culture. In the field females at the end of their second year contained embryos; they produced offspring in the spring of the third year.