CADMIUM ACCUMULATION, DISTRIBUTION AND ELIMINATION IN THE BIVALVE MACOMA-BALTHICA - NEITHER METALLOTHIONEIN NOR METALLOTHIONEIN-LIKE PROTEINS ARE INVOLVED

Accumulation and elimination of cadmium was investigated in the tellinid clam, Macoma balthica (L. ). Accumulation of Cd was linear in soft tissues throughout a 29-day exposure period at 100 mu g Cd liter** minus **1. Loss of Cd, measured after transfer of experimentally-contaminated clams to clean seawater, was exponential and relatively slow. In contrast, Cd uptake onto the shell of Macoma was characteristic of saturation kinetics, indicative of physical adsorption processes. Amounts of Cd accumulated by the shell were low, and the elimination rate rapid (half-time, 7 days) compared with soft tissues. Gel chromatographic profiles of cytosol extracts from control and experimental groups of M. balthica revealed that most of the Cd was bound to high molecular weight ligands, an unusual feature in bivalve molluscs. The metabolism of Cd in M. balthica is different from that reported for other bivalve groups in several respects.