UTTAR PRADESH JOURNAL OF ZOOLOGY

Background: Organophosphate pesticides are among the most pervasive chemical contaminants of freshwater ecosystems in South Asia. In the intensively cultivated rice-vegetable belt of West Champaran, Bihar, small ponds, drainage ditches, and seasonal wetlands lie in close proximity to treated fields, and informal, largely unregulated pesticide use in this region routinely introduces organophosphates such as profenofos into these water bodies; yet the sub-organismal impact of such local contamination on the accessory respiratory organs of resident air-breathing fishes remains poorly characterised.

Objective: The present study evaluated the histopathological and scanning electron microscopic (SEM) alterations in the suprabranchial chamber (SBC) of the obligate air-breathing teleost Channa gachua (Hamilton, 1822) following sublethal exposure (0.06 ppm; 1/10th of 96-h LC₅₀) to the organophosphate insecticide profenofos.

Methods: Fish were collected from freshwater habitats of West Champaran, Bihar, India, acclimated under laboratory conditions, and exposed to profenofos for 10 and 20 days. SBC tissue was processed for H&E histology (seven photomicrographs) and gold-sputter-coated SEM (four micrographs).

Results: Light microscopy of control fish showed a well-organised respiratory epithelium, intact blood vessels, and regular folded lamellae. After 10 days of profenofos exposure, focal detachment of the respiratory epithelium and early vascular engorgement were evident. At 20 days, extensive epithelial erosion, haemorrhage, and architectural disruption were conspicuous. SEM of control tissue revealed regular dome-shaped vascular papillae arranged in rosette islets separated by smooth inter-islet lanes. In treated fish, SEM demonstrated deformation of islets, dilatation of mucous pores, intermingling of papillae and lanes, and extensive surface disorganisation that progressed with exposure duration.

Conclusion: These time-dependent morphological changes collectively indicate potential compromise of the aerial gas-exchange function of the SBC and highlight the ecological risk associated with organophosphate contamination of freshwater environments inhabited by air-breathing fishes.