Effects of heavy metals (cadmium, copper, chromium and lead) on a freshwater snail: Biomphalaria glabrata Say (Gastropoda, Prosobranchia).

This study concerns the effects of heavy metals (cadmium, copper and chromium) on the mortality and fecundity of the adults of Biomphalaria glabrata and the viability of their embryos. Embryos were also tested for lead. The concentrations used ranged from 0 ppm to 4.0 ppm for Cd2+ and Cu2+ and from 0 to 1.4 ppm for Cr6+. Cadmium and copper were far more toxic than chromium. Fertility was abolished by 0.1 ppm of cadmium and copper and fecundity was severely affected by chromium. Some evident sublethal effects were observed. Survival of the hatchlings treated with chromium was of the same order of magnitude as that of the controls and sexual maturity did not show any delay. Forty-one percent of the embryos kept at concentrations of 0.1 ppm Pb2+ completed their development in 51 days, that is, with a delay of 37 days. The hatchlings at 0.1 ppm died after 15 days. The advantages of using freshwater pulmonates as a toxicity test are discussed.