Metal interactions within the kidney,gill, and digestive gland of the clam,Mercenaria mercenaria,following laboratory exposure to cadmium

Mercenaria mercenaria were exposed to 0.1 g Cd/ml seawater (¹⁰⁹Cd + stable carrier) for either (1) periods of 1 hr to 31 days, or (2) a period of 3 days followed by depuration in clean seawater for 2 to 64 days. Cd accumulated at increasing rates in the kidney, but at decreasing rates in all other organs of the clam during the laboratory exposure period. Measurement of total Cd levels confirmed that¹⁰⁹Cd was accumulated by the clam tissues and not simply exchanged. The overall rate of Cd accumulation was significantly greater (P < 0.05) for the kidney than for the gill, mantle, digestive gland, pericardial gland, adductor, or remaining viscera, but not significantly different among the other organs (P > 0.05). No loss of Cd or other detectable metals occurred even after 64 days depuration. The degree to which Cd accumulated in the kidney, gill, and digestive gland did not correlate with the concentrations of other metals already present in these organs (except with Zn in the digestive gland). Negative correlations between different metal concentrations were never observed. Comparison of metal interaction patterns between the kidney, gill, and digestive gland indicates that each organ relies on different mechanisms for sequestering metals.