Sublethal cadmium chloride (0.3 ppm) toxicity induced stress related morphopathological alterations in the
accessory respiratory organ of the air-breathing catfish
Heteropneustes fossilis
(Siluriformes;
Heteropneustidae) have been investigated at various intervals of exposure. The histopathological
manifestation of the cadmium toxicity includes bulging of the hyperemic secondary lamellae into the
lumen of the accessory respiratory organ, necrosis and sloughing of the respiratory epithelium leading to
haemorrhage and fusion of SL at various stages of the exposure. Periodic alterations in the densities of
epithelial cells and mucous cells along with the development of non-tissue spaces have also been noticed at
different exposure periods leading to alterations in the thickness of the respiratory epithelia. The heavy metal
salt exposure has affected the mucogenic activity of the respiratory epithelium not only quantitatively but
qualitatively also, indicating the probable ameliorative role fish mucus in cadmium toxicity.
