Cellular and tissular distribution of copper in an intrasedimentary bivalve, the Baltic clam Macoma balthica, originating from a clean or a metal-rich site

Baltic clams (Macoma balthica) from clean and industrialized areas were exp osed to 30 ng Cu.mL(-1) or 40 ng Cu.mL(-1) for 13 days. Specimens from the industrialized site accumulated less Cu in their soft tissues, suggesting t hat those clams living in a metal-rich area are able to limit metal accumul ation. Cu and metallothionein-like protein (MTLP) levels were positively co rrelated in specimens from the industrialized site only, indicating that pe rhaps living in a polluted area enables them to use this method of detoxifi cation. The contaminated specimens contained Cu-rich microgranules in the b asal lamina and intracellular spaces of digestive gland, labial palps, and gills as well as in lysosomes of the digestive gland and in a few hemocytes . The coexistence of S and Cu suggests that sulfur may be the chelating age nt. As a consequence of detoxified storage, ultrastructural damage was rare ly observed. These Cu deposits, which contributed to the predominance of bi ochemical insoluble forms shown in the whole soft tissues, are generally co nsidered hardly available to predators, whereas soluble Cu (35-38% of total Cu) would most probably be bioavailable.