Responses of hemocytes and gill tissues to sublethal cadmium chloride poisoning in the crabParatelphusa hydrodromous (Herbst)

The hemocytic and gill tissue responses of the crabParatelphusa hydrodromous (Herbst) to a wide range of sublethal concentrations of cadmium chloride (0.02–0.50 M/L) were examined after a 30-day exposure using hemocyte counts (THC and DHC) and lamellar pathology. A continued reduction in the hemocyte counts and selective changes in the numbers of hyalinocytes and eosinophilic granulocytes was evident in the toxified crabs. Under sublethal stress, the hyalinocytes developed eccentric nuclei, granular cytoplasm and membrane blebs. Atypical shape, lobate nucleus, dense cytoplasmic deposits and granuloplasmic vacuoles were frequently observed in the granulocytes. Greater proliferation of prohemocytes and abnormal hemocyte morphology indicated cadmium-induced neoplastic transformation of hemocytopoietic organs. No major structural changes in the gills were noted at 0.02 M CdCl₂. Nodular gill disease (NGD), hemocytic hyperplasia and sloughing of walled off hemocytes were prominant lesions after 0.50 M cadmium chloride exposure.