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

Abstract

Baltic clams (Macoma balthica) from clean and industrialized areas were exposed 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 that those clams living in a metal-rich area are able to limit metal accumulation. Cu and metallothionein-like protein (MTLP) levels were positively correlated in specimens from the industrialized site only, indicating that perhaps living in a polluted area enables them to use this method of detoxification. The contaminated specimens contained Cu-rich microgranules in the basal 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 agent. As a consequence of detoxified storage, ultrastructural damage was rarely observed. These Cu deposits, which contributed to the predominance of biochemical insoluble forms shown in the whole soft tissues, are generally considered hardly available to predators, whereas soluble Cu (35–38% of total Cu) would most probably be bioavailable.