Estimation of sublethal toxicity of zinc chloride by histopathological analysis of fish (Heteropneustes fossilis, Bloch) epidermis

Abstract

The effect of zinc chloride on the outer (OE) and inner (IE) opercular epidermis of Heteropneustes fossilis has been investigated. The main toxicopathological alterations of the OE include extensive intercellular as well as intracellular vacuolization and hyperplasia of the epithelial cells (ECs) with regular exfoliation of round or globular ECs from the skin surface. Splitting of the epidermis from the junction of the outermost (OL) and middle layers (ML) leading to the lifting of the OL is sometimes also noticed. The mucous cells (MCs) show periodic fluctuations in their density and staining properties. Extensive vacuolization of the epidermis along with hyperplasia of ECs along with periodic fluctuations in the density and staining behaviour of the MCs are the main alterations observed in the IE. The mucogenic activity of the IE throughout the exposure period remains mostly above the control level. Hence the damage is comparatively less severe. All these histo-pathological manifestations may be considered for their use for testing the quality of variously contaminated water samples.