Exposure to Treated Sewage Effluent Disrupts Reproduction and Development in the Seasonally Breeding Ramshorn Snail (Subclass: Pulmonata, Planorbarius corneus)

Abstract

Experiments were conducted to assess the impacts of exposure to sewage treatment works (STW) effluent upon the growth, reproductive function, and sexual development of the European mollusc, Planorbarius corneus under seasonally varying temperatures and photoperiodic conditions. In river water, a clear seasonal change in the number and weight of egg masses (during both 2003 and 2004), and in the number of eggs produced, was found, providing evidence for profound effects of both changing temperature and photoperiod on reproduction. Exposure to STW effluent caused disturbances in this seasonal reproductive cycle at all concentrations tested. The effects included significant dose-dependent increases in fecundity and in the overall length of the reproductive cycle in adult snails exposed to both 50% and 100% effluent relative to river water for a period of up to 14 weeks. Disturbances in the development of both the male and female gametes of the both the adult snails and their developmentally exposed offspring were also seen. These effects were more evident in the offspring than in the adults.