Cadmium toxicity to the freshwater amphipod Gammarus pulex (L.) during the moult cycle

SUMMARY. 1. The toxicity of cadmium to mature Gammarus pulex at different stages in the moult cycle is described. 2. Immediate post‐moult animals are significantly more sensitive than intermoult specimens at cadmium concentrations between 1.0 and 0.1 mg 1 −1 but not at 0.03 or 0.01 mg Cd 1 −1 . 3. At a calcium concentration of 40mgl −1 , post‐moult animals undergo recalcification within 7 days and thereafter there is little variation in their response to cadmium. 4. External calcium concentrations of 40 and 115mg 1 −1 do not affect cadmium toxicity but at 180 mg Ca1 −1 the sensitivity of immediate post‐moult specimens is significantly reduced. 5. The results are discussed with regard to the protection of G. pulex by present water quality standards.