Effects of cadmium on metal composition and adenylate energy charge in the sea starAsterias rubens L

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Abstract
Sea stars,Asterias rubens, were exposed to 200 μg Cd/L or fed with mussels which contained about 70 μg Cd/g dry wt. After 5 weeks, cadmium in the pyloric caeca of directly and indirectly exposed sea stars had reached levels of 12 and 9 μg Cd/g dry wt, respectively. For both types of exposure, a reduction of 30% of the zinc levels in the pyloric caeca was found, which was correlated with a comparable displacement of zinc from the metallothionein-like proteins. Copper levels were increased in the pyloric caeca of directly exposed sea stars. In gonads, stomachs, and body wall of directly exposed sea stars, cadmium concentrations were 4 to 9 times higher than those in animals fed with Cd-contaminated mussels. Cadmium exposure also affected metal composition in these tissues. The ovaries contained relatively large amounts of zinc. Gel filtration chromatography revealed that this zinc and the accumulated cadmium were distributed over a large range of high-molecular-weight proteins. Both direct and indirect cadmium exposure resulted in a small, but significant decrease of the adenylate energy charge (AEC) in the pyloric caeca. In the gonads, no effect of the cadmium exposure could be demonstrated on the AEC, but in the ovaries a reduction of the adenylate pool was found. In semi-field experiments, stars were exposed to 25 μg Cd/L or fed with mussels collected from the heavily polluted Dutch Western Scheldt. After 6 months of direct or indirect exposure, cadmium in the pyloric caeca had reached comparable levels of 8 and 7 μg/g dry wt, respectively. In the gonads of sea stars that had been fed with Western Scheldt mussels, cadmium levels were lower than those in directly exposed sea stars, but still about a factor 10 higher than those in unexposed animals. Exposure of sea stars to 25 μg Cd/L for three months, had no effects on the levels of zinc, copper and magnesium or on the AEC in the pyloric caeca.