Assessing the Sublethal Effects of Dibutyl Adipate on Unio Delicatus: Biochemical and Histopathological Insights

Since phthalates, one of the plasticizers and endocrine disrupting compounds, are important chemicals that threaten ecosystem health, adipate derivatives have been developed as alternatives. However, information on the effects of adipates on aquatic organisms, which are nontarget species, is very limited. Therefore, in this study, the acute and sublethal effects of dibutyl adipate (DBA) on the freshwater mussel Unio delicatus were investigated. The 96-h lethal concentration (LC₅₀) of DBA was determined as 1309.64 mg/L. Sublethal effects were determined by biochemical and histopathological examinations following exposure to DBA concentrations of 25 mg/L (1/50 of the LC₅₀) and 65 mg/L (1/20 of the LC₅₀) for 96 h and 21 days. Malondialdehyde levels in the gill tissues of mussels exposed to 25-mg/L DBA increased significantly on the 21 days. Additionally, glutathione levels in the digestive gland and gill tissues of mussels exposed to 25-mg/L DBA increased at 96 h. According to advanced oxidation protein product results, there was a significant increase in the digestive gland tissue at 21 days of exposure for both DBA concentrations, while there was a significant decrease in the gill tissue at 25-mg/L DBA at both exposure times. Although there was no significant change in the total antioxidant status of the hemolymph, the total oxidant status of the hemolymph showed a significant increase over 21 days of exposure and decreased at 96 h of exposure. Histopathological changes were observed only in the gill and digestive gland tissues after exposure to DBA. The fact that exposure to sublethal DBA concentrations caused changes in biochemical and histopathological parameters in mussels suggests that it may have adverse effects on organisms living in aquatic ecosystems.