Physiological and metabolic responses of a freshwater gastropod to fenpyroximate: Insights from respiratory and behavioural alterations

: Fenpyroximate, a pyrazole acaricide widely used in agriculture, may unintentionally reach aquatic environments and affect non-target organisms. The present study evaluated the physiological responses of the freshwater gastropod Filopaludina bengalensis following 96-h exposure to fenpyroximate, focusing on respiratory, metabolic, and behavioural endpoints across juvenile and adult life stages. A concentration-dependent decline in oxygen consumption and metabolic rate was observed, indicating impaired energy metabolism. Behavioural alterations, including reduced crawling and tentacular activity, increased mucus secretion, and impaired retractability, further supported the occurrence of physiological stress. Juveniles exhibited greater sensitivity than adults, as reflected by lower LC50, LOEC, and MATC values. Additionally, molecular docking analysis suggested potential inhibition of mitochondrial complex I, supporting the observed metabolic disturbances. Overall, these findings highlight fenpyroximate-induced physiological alterations in freshwater gastropods and underline the importance of evaluating sublethal responses in non-target aquatic organisms. ENVIRONMENTAL IMPLICATION: Fenpyroximate is widely used in agriculture and may reach freshwater ecosystems through runoff and drift, posing risks to non-target organisms. This study demonstrates that fenpyroximate induces physiological, metabolic, and behavioural disturbances in a freshwater gastropod, with juveniles showing greater sensitivity than adults. Reduced respiration and metabolic impairment suggest disruption of energy metabolism, potentially affecting survival and ecological functioning. These findings highlight the physiological and ecological risks associated with fenpyroximate exposure and support the use of freshwater snails as sensitive bioindicators. Multi-level physiological assessment improves environmental risk evaluation of emerging pesticides in freshwater ecosystems.