BIOACCUMULATION AND METABOLIC EFFECTS OF CADMIUM ON MARINE FOULING DRESSINID BIVALVE, MYTILOPSIS-SALLEI (RECLUZ)

Cadmium (Cd) toxicity and the effect of Cd exposure on oxygen consumpt ion, accumulation and body biochemical composition of a marine dressin id bivalve Mytilopsis sallei were investigated. The 96 h LC(50) of Cd for M. sallei was 0.71 mg/L and the safe concentration was 7.1 mu g/L Exposure of M. sallei to Cd resulted in significant decrease in oxygen consumption with increasing metal concentration. Cd accumulation in M . sallei was sensitive to both concentration and duration of exposure to Cd. In both experiments, the concentration of metal was 3-30-fold h igher than the normal level. The effect of exposure time and concentra tion of Cd on body biochemical composition was also studied in M. sall ei. Both carbohydrates and proteins were utilized in concentration as well as time-dependent exposure of Cd to M. sallei. The ratios of glyc ogen/protein and glycogen/lipid were decreasing with increasing exposu re concentration of Cd. In time-dependent experiments, these ratios we re observed to be decreasing up to the 4th day, but later (10 and 20 d ays) there was a recovery with values almost reaching the normal level for glycogen/protein ratio. The caloric concentration levels were det ermined in M. sallei on exposure to Cd but there was not much change e ither in time- or concentration-dependent exposure of Cd. The results of the present investigation indicate that these bivalves prefer to de pend on carbohydrates and proteins rather than on lipids for their uti lization on exposure to either sublethal or lethal stress of Cd. The d ecrease in oxygen consumption together with the utilization of glycoge n and carbohydrates during Cd exposure suggest that these bivalves mig ht shift to anaerobic metabolism in order to encounter the heavy metal stress in the environment.