How acetamiprid induced toxicity on freshwater mussel: Biomarker and histopathological responses?

This study examines the acute and chronic toxicity, immunological responses, oxidative stress, and histopathological effects of acetamiprid (ACE) on the freshwater mussel Unio terminalis. Laboratory experiments determined the 96-h LC₅₀ value, classifying ACE as moderately toxic to this species. Chronic toxicity tests were conducted using two controls [freshwater and dimethyl sulfoxide (DMSO)] and two ACE concentrations (3.52 mg/L and 6.70 mg/L), with exposure durations of 48 h, 7 days, and 21 days under semi-static conditions. Sublethal effects were assessed by analyzing total hemocyte count (THC), total antioxidant status (TAS), and total oxidative stress (TOS) in hemolymph samples. ACE exposure significantly reduced THC, indicating immunosuppression that could impair physiological functions and immune defense. TAS values remained stable, suggesting robust antioxidant regulation, while prolonged exposure led to elevated TOS levels, indicating oxidative stress and potential cellular damage. Histopathological changes observed included lipofuscin accumulation, hemocytic infiltration, gill tissue degeneration, and tubular degeneration in digestive glands. These results highlight the vulnerability of U. terminalis to ACE exposure and its usefulness as a bioindicator species of aquatic ecosystem health. The study underscores the need for stricter pesticide regulation and further research into chronic exposure and combined chemical effects to protect aquatic biodiversity.