Multi-time point transcriptomics and metabolomics reveals toxic responses of imidacloprid exposure in Aquatica leii (Coleoptera: Lampyridae).

Imidacloprid (IMI), a neonicotinoid insecticide, is broadly applied in crop protection during plant growth. However, its strong water solubility and stability allow it to be transported into aquatic systems via rainfall, drainage, spray drift, and other pathways, causing severe damage to aquatic invertebrates. Limited information exists on the physiological, transcriptional, and metabolic mechanisms of IMI toxicity to aquatic fireflies. The present study investigated how multi-time-point acute IMI stress affected physiology, transcription, and metabolism in Aquatica leii, and confirmed the 96-h LC50 of IMI to A. leii at 10 μg/L. Superoxide Dismutase (SOD), Catalase (CAT) and Peroxidase (POD) activities, together with Malondialdehyde (MDA) content, began to rise within hours following acute IMI stress, peaked within 48 h, and then began to decline. According to transcriptomic analysis, there were much more differentially expressed genes (DEGs) as IMI concentrations climbed. According to bioinformatics analyses, the expression of most DEGs related to the "Longevity regulating pathway - multiple species" progressively increased, peaked at 48 h, and then declined following IMI stress. Metabolomic analysis showed regulation of energy metabolism in A. leii larvae under IMI exposure, including amino acid, carbohydrate, lipid, and nucleotide metabolism, with carbohydrate metabolism mobilized during early-stage stress and lipid metabolism during late-stage stress. Conjoint analysis revealed that IMI exposure perturbs purine metabolism in A. leii, compromising cellular repair and proliferative capacity and, together with concomitant CYP450 system disruption, contributing to underlying circadian rhythm disturbances. Collectively, the findings in the study assist in comprehending the toxic effects of IMI on A. leii from multiple perspectives.