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Specimens of sea bass (Dicentrarchus labrax) were exposed to two different cadmium concentrations (0.5 and 5 μg Cd2+/ml seawater) for a period of 7 days. Cadmium accumulated in the tissues of D. labrax in the following order: kidney > liver > gills at both concentrations. Accumulation patterns in fish exposed to 0.5 μg Cd2+/ml seawater were different with respect to 5.0 μg Cd2+/ml seawater. At both Cd concentrations a similar stress situation occurred during the first 4 hr as noted by the depletion of glycogen stores and the increase in free glucose in the muscle; metallothionein was induced in the liver, but failed to bind all the cytosolic Cd, which was in part bound to high-molecular-weight ligands. Fish recovered from this initial stress situation within 24 hr as indicated by the increase in glycogen and the decrease of glucose. Long-term effects were clearly dependent upon metal concentration: at lower Cd exposure, metallothionein induction increased linearly with time and counteracted the toxic effect of the metal; on the other hand, when fish were exposed to 5.0 μg Cd2+/ml seawater a clear stress occurred at the end of the exposure, as indicated by the notable decrease of glycogen stores, the increase of free glucose, the decrease of AEC in the muscle and the increase of Cd bound to high-molecular-weight ligands in the liver.

In the arcid clam, Scapharca inaequivalvis, cadmium was accumulated in the kidneys, gills, viscera, mantle, foot, muscle and red blood cells. Maximum levels were reached in the kidney (725.70 μ/g dry weight) after 4 weeks exposure to 0.5 μg Cd/ml sea-water. The accumulation was higher during the warm rather than in the cold season and in animals exposed to 0.5 as compared with 0.05 μg Cd/ml sea-water. Concentrations of zinc and copper were unaffected by cadmium treatment, whereas iron levels changed during cadmium exposure. When molluscs were returned to natural sea-water, cadmium levels fell slowly. The metal was found in the cytosolic fraction, bound to a low molecular weight ligand, shown by gel filtration to be a Cd-protein with an apparent molecular weight of 10,000 Da, possibly a metallothionein. Ion exchange chromatography of this protein isolated from the viscera revealed the presence of at least two Cd-binding isoforms; the -SH: Cd ratio of the main isoform was 2.8, the UV spectra presented a strong absorption band at 250 nm.