Histopathological Studies on Nitrite Toxicity to Freshwater Fish, Cirrhinus Mrigala

Abstract

Nitrite is an intermediate component of nitrogenous compound and is a naturally occurring inorganic salt found in industrial effluent as a by product of corrosion inhibitors, production of explosives and used extensively in agriculture for crop fertilization. When used at low doses nitrite is toxic. The effect of nitrite on histopathological parameters were evaluated exposing Indian freshwater fish, Cirrhinus mrigala to a sublethal concentration of nitrite (28.31) ppm for different periods from 7 th to 35 th days. Exposure of fish to nitrite showed changes. During 7 th day exposure, in sublethal treatment, the tubular epithelial cells of the kidney exhibited pyknotic and karyohectic nuclei and distrupted luminal surface was observed. Further the kidney showed tubular necrosis, hyaline droplets degeneration, and renal tubular separation as the exposure period extended (14 th and 21 st days). At the end of 20 th day, kidney showed marked contraction of glomeruli, dissolution of lymphoidal tissues and its replacement of blood forming sinuses, leading to formation of cellular debris, tubular necrosis and renal tubular separation. At the end of exposure period (35 th day), kidney appeared spongy and friable; the glomeruli were conspicuously shrunken and collapsed, pyknotic nucleus in tubules, coagulative necrosis, nuclear pycnosis, renal tubular separation and hyaline droplets degeneration.In control fish, the histology showed normal disposition of renal tubules, glomeruli and interspersed lymphoid tissue. In acute treatment (24h) the glomeruli of kidney contracted markedly resulting in a wide gap between the capsular walls, extensive degeneration of lymphoid tissue and nephric tubules were noticed