Early-life stages amplify the ecotoxicological vulnerability of freshwater gastropods to the agricultural fungicide prochloraz.

Prochloraz (PCZ) is a widely used imidazole fungicide, but its ecological hazards to nontarget freshwater gastropods in paddy-field aquatic environments remain insufficiently understood. This study evaluated developmental stage-dependent acute toxicity and adult sublethal responses to PCZ in Pomacea canaliculata. Newly hatched juveniles were more sensitive to PCZ than adults, with nominal concentration-based 96 h median lethal concentration (LC₅₀) and median concentration for composite physiological inhibition (IC₅₀) values of 0.51 and 0.46 mg L⁻¹ , respectively, compared with 2.62 and 1.84 mg L⁻¹ in adults. PCZ also induced escape behavior, composite physiological inhibition, and reduced survival in both life stages. During 21 d chronic exposure, adults showed inhibited shell-height and body-weight growth. After 48 h exposure, hepatopancreatic ROS levels increased, especially at 0.5-2.0 mg L⁻¹ , accompanied by gene-specific antioxidant responses, including upregulation of SOD and GPx at selected concentrations, suppression of CAT, and downregulation of GST at higher concentrations. Representative qualitative histopathological observations provided supportive evidence of multi-tissue structural alterations in adults. Overall, PCZ induced stage-dependent toxicity in P. canaliculata, with early-life stages being more vulnerable than adults. These findings suggest that incorporating early-life-stage endpoints may improve laboratory hazard identification of PCZ in freshwater gastropods, while field-level ecological risks require further evaluation under environmentally realistic exposure scenarios.