Manimekalai, D.; Srinivasan, A.; Padmavathy, P.; Jawahar, P.; George, R., and Arisekar, U., 2022. Acute and chronic toxicity effects of the heptachlor pesticide on tilapia (Oreochromis mossambicus): Impact to behavioral patterns and histopathological responses. Journal of Coastal Research, 38(5), 999–1010. Coconut Creek (Florida), ISSN 0749-0208.

Heptachlor is an organochlorine (cyclodiene) insecticide that enters water bodies and affects aquatic organisms such as fishes and shellfishes. Due to its persistent nature, it spreads from the source of its use and pollutes the area. The toxic effect of heptachlor on histopathological changes in the gill, liver, kidney, and muscles of tilapia Oreochromis mossambicus were studied. The experimental fish were exposed to four concentrations of heptachlor, viz., 0.756, 1.513, 3.025, and 6.050 ppm, for a period of 96 hours during an acute toxicity test. In the current study, the lethal concentration (LC50) value of heptachlor on tilapia at 96 hours was calculated as 4.006 ppm. Fish were subjected to three different concentrations of heptachlor (0.2003, 0.4006, and 0.8012 ppm) based on the LC50 value to study the long-term effect of heptachlor. Histological changes such as lamellar fusion, lamellar cell hyperplasia, degenerated secondary gill lamellae; Bowman's space dilation and renal tubules detachment; hepatic cells death, melanomacrophage formation, and multifocal degeneration of myocytes; and myoepithelium vacuolation were observed in the gill, kidney, liver, and muscles, respectively, during acute and chronic exposure to heptachlor. The toxicity study revealed that the heptachlor pesticide is highly toxic to tilapia even at a minimum concentration of 0.756 ppm. Hence, it is suggested that care must be taken not to allow the entry of pesticides into the habitat of fishes.

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