Impact of Nitrite Toxicity on Histopathological Profile To Freshwater Fish, Cirrhinus Mrigala

-------------------------------------------------------ABSTRACT--------------------------------------------------The present study was to evaluate nitrite toxicity in fish gills during long-term exposure of sublethal concentration of sodium nitrite (NaNo2). The effect of nitrite on histopathological parmeters were evaluated exposing Indian freshwater fish, Cirrhinus mrigala to a sublethal concentration of nitrite (28.31ppm) for different period from 7 to 35 days (7, 14, 21, 28, 35) days. During 7 day exposure, the primary gill lamellae swollen due to hyperplasia of epithelial cells. At the end of 14 day, mucous cells were located in the secondary lamellae and on 21 and 28 day hypertrophied epithelial, lamellar hyperplasia in the middle part of secondary lamella, epithelial lifting, aneurysms lifting, lamellar fusion, and bulging was detected. The observed changes were severe as the exposure period of gill at the end of 35 days.