Effects of chronic cadmium exposure on crayfish survival, growth, and tolerance to elevated temperatures.

Crayfish Cambarus latimanus were subjected over a 5-month period to 0.02, 5, and 10 microgram Cd/L in a continuous flow system at ambient winter temperatures. Uptake of cadmium, growth, and mortality were measured. One-half of the surviving crayfish were analyzed for Cd after completion of the 5-month experiment, while the remaining half were removed from the contaminated water and subjected in a static laboratory experiment to stepwise, daily increases in temperature. The results indicated that (1) the rate of Cd uptake in crayfish was positively related to external concentration, (2) mortality increased significantly with higher Cd concentrations, and (3) neither growth nor thermal tolerance was significantly related to the Cd concentration in the crayfish tissues. The importance of chronic, low-level studies is discussed.