Triazophos toxicity induced histological abnormalities in Heteropneustes fossilis Bloch 1794 (Siluriformes: Heteropneustidae) organs and assessment of recovery response

Abstract Background Agricultural pesticides have toxic effects in the aquatic ecosystem, and their persistence poses a hazard to aquatic life, as seen by fish poisoning, both acute and chronic. Triazophos, a broad-spectrum organophosphate insecticide, is used to control agricultural crops from insect pests. For a period of 10 days, Heteropneustes fossilis , a fish of great economic and therapeutic value, was exposed to various levels of triazophos toxicity (5, 10 and 15 ppm), after which they were sacrificed. For recovery tests, the treated fish were switched to clean tap water after 10 days of exposure to the toxicant, examined for another 10 days, and then sacrificed. The histological changes in the tissues of the sacrificed fishes' gill, liver, intestine, kidney, brain, and muscle (treatment and recovery) were investigated. Results The histology investigations revealed that the toxicant was hazardous, with histopathological changes increasing as the concentration of the toxicant increased. The gills had the most damage, with fusion of secondary lamella and epithelial hyperplasia; liver had vacuolization, pyknotic nuclei, and focal necrosis; intestine had degenerated, necrotic villi, degeneration of epithelial cells, and atropy; kidney had narrowing of the tubular lumen, pyknotic nuclei, hypertrophy, degeneration; swelling, haemorrhage, larger neuronal cells, and karyolysis were observed in the brain, whereas infiltration of leucocytes, loss of striated muscles, and an increase in intra fibril area were observed in the muscle. When compared to the treated fishes, the 10-day recovery research demonstrated tissue damage and a slower recovery pattern. Conclusions Triazophos caused histological changes in the gill, liver, intestine, kidney, brain and muscle of the test fish Heteropneustes fossilis . With reference to recovery response, a slow recovery was observed. Furthermore, this is the first investigation into the effects of triazophos on the recovery response in Heteropneustes fossilis .