Comparative study of the accumulation and detoxification of Cu (essential metal) and Hg (nonessential metal) in the digestive gland and gills of mussels Mytilus galloprovincialis, using analytical and histochemical techniques

The aim of the present study is the comparative examination of accumulation and detoxification of Cu and Hg in digestive gland and gills of mussels Mytilus galloprovincialis, using atomic absorption spectrophotometry and autometallography. Mussels were exposed to 0.08 mg L−1 Cu, 0.08 mg L−1 Hg, as well as to a mixture of 0.08 mg L−1 Hg and 0.08 mg L−1 Cu for 11 d. After the experimental exposure, animals were kept under laboratory conditions for a detoxification period of 7 d. An antagonistic effect of Cu against to Hg accumulation was noted in the digestive gland of mussels after the experimental exposure, as well as after the detoxification period, supporting the protective role of Cu against to Hg toxicity in this tissue. Digestive gland was suggested as a main organ for Hg accumulation and gills as a target position for Cu accumulation. Additionally, lower time was evaluated for Hg detoxification in the digestive gland and gills of mussels, in relation to those addressed for Cu detoxification in the same tissues. The evaluation of black silver deposits (BSD) extent performed in digestive gland and gills was suggested as a less sensitive approach, in relation to atomic absorption spectrophotometry (AAS), to indentify the concentration of heavy metals in tissues of mussels. The toxic effects of Hg, Cu and a mixture of them on lysosomal system of the digestive cells are also discussed.

Research highlights
► Antagonistic tendency of Cu against to Hg accumulation in the digestive gland.
► Digestive gland and gills as accumulative organs for Hg and Cu, respectively.
► The detoxification time for Hg was lower, compared to those assessed for Cu.
► BSD extent does not identify particular heavy metals in soft tissues of mussels.
► Protective role of Cu against to Hg toxicity in the digestive cell lysosomes.