ABSTRACT

Aquatic ecosystems are exposed to various pollutants like pesticides and have become a significant environmental concern, with their presence in water bodies posing a threat to aquatic organisms. In real-life, pesticide exposure often is already a mixture of multiple co-occurring compounds with repeated exposure timeframes which disrupt aquatic microbial communities, affecting their function and structure. This study aimed to investigate the effects of a mixture of chlorpyrifos and cypermethrin on thyroid function levels in Clarias gariepinus, an economically and ecologically important fish species. Fish were exposed to cypermethrin and chlorpyrifos in both single and binary mixtures at concentrations of 15, 30, and 45 µL and 20, 40, and 60 µL, respectively, for 96 hours. Thyroid hormone levels including Thyroid stimulating Hormones (TSH), triiodothyronine (T3) and thyroxine (T4) were measured after the exposure period to assess the impact of the pesticide mixture on thyroid functions. The results revealed a concentration-dependent decrease in T3 and T4 levels in fishes exposed to the pesticide mixture. Fish exposed to higher concentrations of chlorpyrifos and cypermethrin exhibited a more pronounced reduction in thyroid function levels compared to the control group. Thyroid hormones play a crucial role in regulating metabolism, growth, and development in fish, and any disruption to their levels can lead to adverse physiological effects. This study shows that the mixture of chlorpyrifos and cypermethrin has the potential to disrupt thyroid function in Clarias gariepinus.