How Permethrin Affects Freshwater Mussels: Physiological, Biochemical, and Histopathological Analyses?

Freshwater mussel Unio delicatus is a species found in aquatic ecosystems in countries bordering the Mediterranean Sea. Permethrin is a synthetic pyrethroid and a widely used chemical in domestic, industrial, and agricultural areas due to its insecticidal properties. Therefore, it is one of the substances that inevitably contaminate aquatic ecosystems and is a chemical whose effects on different types of nontarget aquatic organisms are investigated. In the present study, the sublethal effects of permethrin on the physiological, biochemical, and histological properties of U. delicatus were investigated with two different exposure times. Permethrin was less toxic than other commonly used insecticides against U. delicatus, and its 96-h LC₅₀ value was 119.4430 μg/L. In 96-h and 7-day exposure to permethrin with ¹/₁₀, ¹/₅₀, and ¹/₁₀₀ concentrations, a decrease in total hemocyte count occurred compared to control groups, whereas hemolymph fluid biochemical parameters showed an increase in total antioxidant and total oxidant levels depending on the concentration. In addition to these biochemical results, there were changes in total glutathione, advanced oxidative protein products, and malondialdehyde levels in the gill and digestive gland tissues compared to the control groups. In the gill, digestive gland, connective tissue, and ovaries, ¹/₁₀ and ¹/₅₀ concentrations of LC₅₀ caused pathological findings in both exposure periods. All these data showed that permethrin has significant sublethal effects on U. delicatus. The results of this study provided a comprehensive understanding of the effects of permethrin on nontarget organisms such as U. delicatus.