EFFECTS OF WATER-BORNE CADMIUM ON THE SKIN OF THE COMMON CARP (CYPRINUS-CARPIO)

The skin of carp, Cyprinus carpio, was studied at the ultrastructural level after exposure of the fish to low and high concentrations of cad mium in the water (22 and 560 mug/L, respectively) for different perio ds. The effects of the low concentration of cadmium were similar to th ose of the high concentration, although they appeared later. The basal lamina and the skin surface became highly undulating. Chloride cells appeared between the pavement cells. Necrotic pavement cells were seen from the first day on, while apoptotic pavement cells appeared after several days. Filament cells contained many electron-transparent and e lectron-dense secretory vesicles. Mitotic cells were commonly seen, ma inly in cells adjacent to club cells or close to the epidermal surface . Mucous cells differentiated close to the skin surface. They became e longated and synthesized highly electron-dense mucosomes. The epidermi s became infiltrated by many leucocytes. As the experiment progressed, many leucocytes degenerated, and their remnants were found within mac rophages and club cells. Fibroblasts displayed intense synthesis and, in fish from the low cadmium concentration, deposited a dense network of collagen fibers in the dermis. Melanosomes were located in the exte nsions of melanocytes. In these cells aggregation of melanosomes and a poptotic processes were common. Several of these changes were observed earlier under the impact of stressors other than cadmium. Some change s, such as the appearance of tumorlike bodies at the skin surface, the appearance of Merkel cells throughout the epidermis, and the coupling of leucocytes, may be specific for cadmium.