LIFE-HISTORY AND POPULATION-DYNAMICS OF THE EXOTIC SNAIL POTAMOPYRGUS-ANTIPODARUM (PROSOBRANCHIA, HYDROBIIDAE) IN LAKE PURRUMBETE, VICTORIA, AUSTRALIA

The density, population size-structure, and fecundity of the exotic sn ail Potamopyrgus antipodarum are described, for a period of two years, on two shores subject to different levels of disturbance in Lake Purr umbete. The population dynamics of Potamopyrgus antipodarum showed the same seasonal pattern in the numbers of embryos carried per individua l female in both years, but seasonal patterns in density and potential reproductive output of the population differed between shores. Densit ies of Potamopyrgus antipodarum were high, with a trend for highest de nsities to occur in spring and summer. The population consisted almost entirely of females, which is indicative of a parthenogenic mode of r eproduction. Fecundity was high, with the number of embryos carried pe r female peaking in spring. In summer, the population was dominated by small individuals, but some small snails were present at all times of the year. Potamopyrgus antipodarum was found to be a very successful invader of Lake Purrumbete, with high densities, high fecundity, parth enogenesis and the presence of embryos throughout the year contributin g to this success.