CADMIUM IN THE GASTROPOD LITTORINA-LITTOREA

Tissues of Littorina littorea (Mollusca: Gastropoda) were processed fo r electron microscopy with an aqueous fixative which included hydrogen sulphide to precipitate intracellular cadmium. The procedure retained cadmium in the cytosol, where it was below the detection limit for x- ray microanalysis, but it did not increase the retention of the metal within lysosomes and other sites of accumulation where it was detectab le. Aqueous fixation caused extraction of labile elements, particularl y magnesium and potassium, and this effect was increased by the use of hydrogen sulphide. Cadmium and hydrogen sulphide had disruptive effec ts on the fine structure of cells. It is concluded that cytological fi xatives should not include hydrogen sulphide, and that cryo-fixation i s required for x-ray microanalysis of intracellular elements. Sites of intracellular accumulation of cadmium are described. A scheme is prop osed to show the distribution of the metal between tissues and to acco unt for the slow rate of loss from the animal.