Effect of Exposure and Withdrawal of Disodium Arsenate Heptahydrate on Gills of Highly Nutritious Catfish Clarias batrachus.: A Histopathology and Histochemical Study

Gills, the main respiratory organs of Clarias batrachus; local name MANGUR are studied after long-term exposure (90 days) and withdrawal (90 days) of sublethal concentration (1 ppm; 1/10th of LC50 for 96 hours) of disodium arsenate heptahydrate using histopathological and histochemical techniques. Gills of C. batrachus are lodged in suprabranchial chamber located on either side of the head and hence always remain in direct touch with external aquatic stressors including the arsenic salts. Following exposure, extensive congestion and wear and tear in the blood channels of the secondary gill lamellae are noticed. Normal ladder like configuration of vascular component of the gills gets dismantled leading to haemorrhages and oozing of blood on the gill surface. Damaged gills often show the fusion of adjacent primary gill lamellae at certain places. Density and area occupancy and staining properties of mucous cells are altered and show extensive periodic fluctuations at various periods of exposures. The staining property of the mucous cells and their secretions on surface is however more inclined towards the sulphated glycoproteins indicating their requirements for metal binding and removal. Ninety (90) days of exposed fish when returned to normal tap water showed significant but incomplete recovery among the gill filaments. Epithelial cell hyperplasia still persists. Mucogenic properties of gills continued to remain altered.