Ultrastructural localization of heavy metals (Hg, Ag, Pb, and Cu) in gills and digestive gland of mussels, Mytilus galloprovincialis (L.)

The intracellular localization of heavy metals using autometallography (AUM) was studied in the gills and the digestive gland of the common mussel Mytilus galloprovincialis, after an experimental exposure to 0.1 mg L-1 of Hg, 0.1 mg L-1 of Ag, 0.1 mg L-1 of Pb, and 0.1 mg L-1 of Cu for 98 days. In the gills, autometallographical black silver deposits (BSDs) were localized in the dense bodies observed in the apical and in the basal part of the cells. Among metals, Hg presented the highest accumulation, followed by Ag, Pb, and Cu. BSDs were more prominent in the abfrontal part of the gill filament in the case of Hg exposure and in the frontal part in the case of Ag and Pb exposure. In the digestive gland, Hg and Ag were localized in the heterolysosomes and the residual bodies of the digestive cells, as well as in the dense bodies of the basophilic cells. The heavy metal exposure also affected the gross morphology of the examined tissues and resulted in the fusion of residual bodies in the digestive cells, the fragmentation or vacuolization of the rough endoplasmic reticulum, and the increase in the number of granules in the basophilic cells. In the gills, fusion of the gill filaments was also noted.