Accumulation of copper and histopathological alterations in the oyster Crassostrea angulata

Abstract

Specimens of Crassostrea angulata were exposed to sublethal copper concentrations (200 and 600 μgL^–1 Cu²⁺) during 2 to 30 days. The accumulation of copper and histopathological effects on the gills, digestive gland and heart were studied. The highest copper concentrations were found in the gills, with values over 2 mg g^–1 dry weight for organisms exposed to the highest concentration at the end of the exposure period (day 30). In the digestive gland, the concentration was 1 mg g^–1 dry weight (highest exposure on day 30). The rate of bioconcentration (BC_r, defined as the concentration in the tissue at an exposure concentration at time t minus the mean concentration of the control throughout the experiment, divided by the exposure time) decreased in both tissues. The values ranged from 392 to 57 μg g^–1 day^–1 for gills and from 133 to 18 μg g^–1 d^–1 for the digestive gland. In the gills, specimens exposed to 200 μg L Cu²⁺ showed disorganization and apical alterations of the cilia cells and hyperplasia, lamellar fusion and lamellar loss in organisms exposed to 600 μg L^–1 Cu²⁺. In the digestive gland, specimen exposed to 200 μg L^–1 Cu²⁺ showed hemocytic infiltration in the underlying connective tissue and numerous brown cells compared to the control specimens. On the other hand, thinning of the epithelium of the digestive tubules, occlusion in the lumen of some primary tubules and dilation of the digestive ducts occurred in organisms exposed to 600 μg L^–1 Cu²⁺. The heart of oyster exposed to copper showed thinning of the epithelium of the auricles and ventricle and an increase in brown cells on the walls of the auricles, as well as connective tissue destruction in the auricles and ventricle.