Effects of cadmium on the predator-prey interaction between the turbellarian Dendrocoelum lacteum (M�ller, 1774) and the isopod crustacean Asellus aquaticus (L.)

Abstract

The toxicity of cadmium to the freshwater triclad turbellarian Dendrocoelum lacteum and the isopod crustacean Asellus aquaticus was determined for each species when maintained individually (96 h LC50 for D. lacteum, 23.22 mg Cd/L, and for A. aquaticus, 0.16 mg Cd/L) and when kept together. When exposed together over a concentration range of 20–100 μg Cd/L, the effect of this predator-prey system was, as expected, i.e., direct toxicity to A. aquaticus, but there was also a reduction in the predation rate by D. lacteum. Both responses increased with increasing toxicant concentration. The possible causes of these observed effects, including the diet of A. aquaticus, cannibalism by A. aquaticus, and speed of the predator, are discussed. The possible ecological consequences of removing either predator or prey from a freshwater ecosystem as a result of a pollution incident are also considered.