Structural and Histopathological Responses of Gill Tissue in Channa punctatus under Chlorpyrifos Stress

Author(s): Dr. M Sunanda

Abstract:

Freshwater fishes are continuously exposed to pesticide residues released into aquatic ecosystems through agricultural runoff, posing serious risks to non-target organisms. Chlorpyrifos, a commonly used organophosphate insecticide, is known to induce toxic effects in fish, particularly in organs directly interacting with the aquatic environment. The present study investigates the structural and histopathological responses of gill tissue in Channa punctatus following exposure to chlorpyrifos, with emphasis on tissue-level alterations as indicators of toxic stress. Gill tissues from control and chlorpyrifos-exposed fish were examined using standard histological techniques. Control specimens exhibited well-organized primary and secondary lamellae with intact epithelial lining and distinct interlamellar spaces, reflecting normal gill architecture. In contrast, fish exposed to chlorpyrifos displayed pronounced histopathological alterations. Sub-lethal exposure resulted in shortening and partial fusion of secondary lamellae, epithelial degeneration, bulging of filament tips, and cytoplasmic vacuolization, indicating early cellular stress. Lethal exposure caused severe disruption of gill structure, characterized by extensive lamellar fusion, curling and clubbing of lamellae, epithelial lifting, hyperplasia, hypertrophy, necrosis, vacuolization, and nuclear abnormalities such as pyknosis. Many of the observed changes appear to represent adaptive defense mechanisms aimed at reducing toxicant entry, while prolonged exposure led to irreversible pathological damage. These structural alterations significantly compromise respiratory efficiency and ionic regulation, ultimately affecting fish health and survival. The study highlights the sensitivity of gill histopathology as a reliable biomarker for assessing chlorpyrifos toxicity and underscores the need for controlled pesticide usage to safeguard freshwater ecosystems.

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