TISSUE AND CELL DISTRIBUTION OF COPPER, ZINC AND CADMIUM IN THE MUSSEL, MYTILUS-GALLOPROVINCIALIS, DETERMINED BY AUTOMETALLOGRAPHY

The localization of metals in selected tissues of metal-exposed mussel s was investigated by means of autometallography. Mussels collected fr om a Zn-polluted site were (a) depurated or, alternatively, (b) expose d to either Cu, Zn or Cd for 41 d. Mussels collected from a clean site were used as experimental reference. Autometallographically demonstra ted black silver deposits (BSD), indicating the presence of metals, we re observed in gills, (a) in frontal cells and haemocytes of Cu-expose d mussels, (b) in secretory postlateral and abfrontal cells and in end othelial cells of Zn-exposed mussels, and (c) in frontal, postlateral and endothelial cells but mainly in abfrontal cells and haemocytes of Cd-exposed mussels. Autometallography also revealed the presence of BS D in connective tissue brown cells underlying the mantle. Additionally , adipogranular cells of the connective tissue surrounding the gonad f ollicles were positively stained but no BSD was found in gonad tissue. Scarce BSD were found in the cytoplasmic granules of the stomach wall of control mussels whilst depurating and metal-exposed mussels exhibi ted BSD lining the apex of the stomach epithelial cells. Contrary to t he results previously obtained with marine gastropod molluscs, BSD wer e not found in the basal lamina of digestive tubules, stomach, and duc ts of mussels. Highly conspicuous BSD were observed in digestive cell lysosomes of depurating and metal-exposed mussels. Basophilic cells we re always devoid of BSD. Finally, BSD were also found in nephrocyte ly sosomes and mineralized concretions.