Histopathological changes induced by ambient ammonia (ammonium sulphate) on the opercular linings of the catfish Heteropneustes fossilis

Acute toxicity of 2 g l super(-1) (LC sub(50)) ammonium sulphate on the outer and inner epithelial linings of the operculum of the air-breathing catfish Heteropneustes fossilis (Bloch) at different intervals of exposure was studied using histochemical techniques. The inner and outer epithelial linings showed different responses to the corrosive action of the inorganic fertilizer. The outer epithelial lining exhibited massive and quicker damage due to necrosis and sloughing of its surface epithelial cells along with degeneration and disappearance of the club cells. Simultaneous regeneration of various cellular elements of the epidermis was also observed. There were comparatively very few necrotic changes in the cellular constituents of the inner epithelial lining. The alterations observed include hyperplasia of the epithelial cells (which showed accumulation of glycogen granules) and periodic increases followed by decreases in the density and size of the goblet mucous cells.