Cadmium kinetics in freshwater clams. I. The pattern of cadmium accumulation inAnodonta cygnea

Freshwater clams (Anodonta cygnea) were exposed to cadmium under laboratory conditions. Time courses of Cd accumulation were determined for whole animal and the separate organs. At 5 g/L, Cd accumulation proceeded mainly linearly. At 25 g/L, the accumulation pattern was biphasic for whole animals and most of the organs: during the first four weeks Cd concentrations increased linearly, remaining at a constant level for the next two weeks. Thereafter, metal concentrations increased strongly until, after 10 weeks, a saturation level was reached. It is argued that the biphasic course of accumulation is not caused by an advancing selection through mortality or by the gradually decreasing mean animal weight, nor by the typical laboratory conditions of absence of food and substratum. The partition of total Cd among the organs gradually changed over the first eight weeks, remaining constant from that time. The ultimate order of Cd concentrations was: gills > labial palps > mantle-edge > mantle, kidney, whole animal > midgut gland > guts/gonads complex > foot. A possible relation between the time course of Cd accumulation and behavioral responses is presented.