Toxicity of cadmium and zinc to miracidia of Schistosoma mansoni

Abstract

The speci®c objectives of this study were to elucidate metal toxicity to hatching, survival and avoidance behaviour of Schistosoma mansoni miracidia. The toxicity of cadmium, zinc, and cadmium}zinc mixtures at concentrations ranging from 10000 to 10 lg}l was nvestigated. Metal mixture toxicity investigation was undertaken with equal concentrations of the metals. The hatching of miracidia from eggs was inhibited by concentrations of 1000±10000 lg}l of single metals. Metal mixtures had no effect on egg hatching. Survival of miracidia was reduced by increasing metal concentration except at concentrations of 10 lg}l for single metal toxicity where survival was increased above the control. Miracidia demonstrated a rapid avoidance behaviour when brie¯y exposed to heavy metals. The mechanisms of metal toxicity to miracidia are brie¯y discussed.