Histopathological and Fatty Acid Alterations in Gammarus Lacustris Exposed to Commercial-Grade Imidacloprid

Abstract

Imidacloprid is frequently detected in freshwater ecosystems; however, information on its sublethal effects in non-target amphipods remains limited. In this study, the effects of environmentally relevant concentrations of imidacloprid (16 and 160 & micro;g/L) on Gammarus lacustris were evaluated using an integrated histopathological and fatty acid (FA) composition approach. After a 14-d exposure period, significant lesions were observed in the gill and hepatopancreas tissues (p < 0.005), including epithelial hypertrophy, hemocoelic atrophy, vacuolization, and necrosis. Analyses of FA composition revealed significant alterations (p < 0.05), characterized by reductions in n-3 polyunsaturated FAs (PUFAs) and changes in the n-3/n-6 ratio. Multivariate analyses (principal component analysis [PCA] and partial least squares discriminant Analysis [PLS-DA]) revealed a clear dose-dependent segregation (70% variance). Notably, hierarchical clustering showed a strong positive correlation between tissue damage and PUFA mobilization. Overall, the concurrent presence of tissue-level damage and changes in FA composition indicates that sublethal imidacloprid exposure exerts pronounced adverse effects on G. lacustris. These findings support the use of amphipods as sensitive bioindicators of pesticide contamination and highlight the potential ecological risks associated with neonicotinoid residues in freshwater environments.