Branchial pathogenesis in a freshwater fish, Puntius conchonius Ham., chronically exposed to sublethal concentrations of cadmium.

Effects of sublethal concentrations, 630 and 840 micrograms/liter (0.05 and 0.066 fractions of the 96-hr LC50), of cadmium chloride on the gills of a freshwater fish, Puntius conchonius, were examined light microscopically during a 12-week exposure. The secondary gill lamellae showed disrupted epithelium, necrosis, accumulation of cellular debris, capillary congestion, and wilting of the pillar cell system. Hypertrophy and hyperplasia of chloride cells as well as partial or complete fusion of secondary lamellae also occurred in the Cd-exposed fish. Branchial lesions together with coagulation film anoxia are likely to result in serious respiratory distress and related tissue hypoxia.