Histopatholoical Changes Associated with Sub-lethal Ammonia Toxicity in Fingerlings of the Indian Major Carps

Abstract

Histopathological changes associated with ammonia toxicity were studied in fingerlings of Catla catla, Labeo rohita and Cirrhinus mrigala. The fingerlings of each species were exposed to increased sub-lethal concentrations, viz., 1, 2, 4, 8, 11.8 and 16 mg/l] of total ammonia nitrogen (TAN) and the toxic effects were studied through histology of gill, liver, kidney, brain and muscle. Mild to severe histopathological changes, almost identical in all the three species, were discernible with the increasing ammonia concentrations. Changes in gill included hypertrophy, engrossment of cartilage cells, hyperplasia of the primary and secondary lamellae, engrossment of blood vessels with leukocytes and loss of pillar cells. Early degenerative changes in liver were observed in all the species exposed to 1-8 mg/l TAN while complete distortion of the cellular architecture of hepatocytes, severe vacuolations and intracellular oedema and dilation of central vein were observed in 11.8 and 16 mg/1 TAN. Histological changes in kidney was observed in the fingerlings in lower concentrations (2-8 mg/l) of TAN exposure which included mainly necrosis of renal tubules, glomerulonephritis and appearance of haemopoietic tissues. Large scale degeneration of renal tubules, moderate to massive infiltration of macrophages and mononuclear cells into lumen of the renal tubules and engrossed blood vessels were observed in 11.8 and 16 mg/! TAN. Remarkable changes in the brain and muscle were recorded at 8 mg/l and higher TAN concentrations while no appreciable changes were noticed in lower concentrations of TAN.