Cadmium and Zinc content was determined in organs of the Japanese scallop Mizuhopecten yessoensis, collected in 1984 from the Sea of Japan and aged between 1 and 8 yr. Under conditions of background Cd, Cd concentration in hepatopancreas and kidney increased linearly with age from 39 to 400#gg -1 dry wt in hepatopancreas, and from 100 to 640/~g g-1 dry wt in kidney. Such a pattern was not determined for Zn. Cd concentration in muscle, mantle and gill did not exceed 6/~g g -t dry wt in the oldest scallops. In subcellular fractions of the hepatopancreas, cytosolic Cd accounted for 71.7% in l-yr-old scallops and 98.8% in 8-yrolds. A similar ratio was established for gills, although gill Cd content was an order of magnitude lower. Analysis of Cd distribution in cytoplasmic proteins (of different molecular weight) in the hepatopancreas, showed that the amount of Cd bound to metallothionein-like proteins increases with scallop growth. A considerable amount of Cd also was detected in high molecular weight proteins. Thus, Cd accumulation, with age, in organs of the Japanese scallop is due to metal binding by cytoplasmic proteins.

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The activity of acid and alkaline phosphatases, glucose-6-phosphatase. ~g~+ -~T P a s e and glucose-6-phosphate dehydrogenase was investigated in embryos and larvae obtained from gametes of the sea urchin Strongylocentrotus nudus exposed for 30 d to increased zinc, copper and cadmium concentrations (100, 25 and 50 ltg 1-l. respectively). Exposure of parent sea urchins to zinc resulted in increased M g 2 + -~T P a s e activity and decreased glucose-6-phosphate degydrogenase activity in larvae at the stage of 2 d pluteus, followed by their death. Exposure of parents to copper resulted in accelerated development of larvae at the stage of early pluteus; exposure to cadmium led to no visible changes in larval development.

Effects of low cadmium concentrations (0.5 pg Cd 1 ' ) on uptake, alkaline phosphatase activity and zinc content of scallops Patinopecten yessoensis were investigated during 25 d exposure. Cadmium accumulations in digestive gland were bound to cytoplasmic intermediate molecular weight proteins. No adverse damage was observed.

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