TOXICOPATHOLOGICAL IMPACT OF CADMIUMCHLORlDEONTHE ACCESSORY RESPIRATORY ORGAN OF THE AIR-BREATHING CATFISH HETEROPNEUSTES FOSSILIS

Sublethal cadmium chloride (0.3 ppm) toxicity induced stress related morphopatholo gical alt erations in th e accessory respiratory organ o f the air-breathing ca tfish Heteropneustes f ossilis (Siluriforrnes; Heteropneus tidae) have been investigated at various intervals of exposure. The histop ath ologic al mani festati on of the cadmium toxicity inc ludes bulgin g of the hyperemic secondary lamell ae into the lumen of the ac ce ssory respira tory or ga n, necro sis and sloughing of the respiratory epithelium leading to haemorrhage and fusi on of SL at various stag es of the expos ure. Periodic alterations in the densities of epithelial cells and mucous cells along with the development of non-ti ssue spaces have also been noticed at differe nt exposure periods leading to alterations in the thickness of the respiratory epithelia. The heavy metal sa lt exposure has affected the muco genic activity of the respiratory epithelium not only quantitativ ely but qualitatively also, indicating the prob able ameliorative role fish mucu s in cadmium toxicity .