Effect of The Nitrate Fertilizer Urea on the Ultrastructural Changes In The Gill Of Freshwater Fish Catla

Ultrastructural study of the gill of Catla catla on exposure to 10% LC50 sublethal concentration of nitrate fertilizer urea was carried out. Hypertrophy and hyperplasia of the lamellar cells in combination with epithelial lifting and edema were noticed. Necrosis of pillar system with lamella resulted in blood congestion and even an aneurism. Hyper secretion of mucous on the epithelium is to protect against environmental alteration was also determined. Infiltrated macrophages and leucocytes in the lamellar tissue were observed which was a compensatory repair response to tissue damages. Apoptotic condition of the cell is evident by clumping of chromatin, swelling of nucleus and mitochondria.