Chronic Imidacloprid Exposure Impairs Chironomid Emergence via the Calcium-ROS-Fatty Acid Axis in a Lifecycle Assessment

While mitochondrial toxicity of neonicotinoids from acute, high-dose exposure has been reported, their role in developmental toxicity to aquatic insects under chronic, environmentally relevant concentrations remains unclear. We aimed to elucidate the chronic toxic mechanism of imidacloprid in Chironomus kiiensis and distinguish its acute and chronic mitochondrial toxic pathways. Here, C. kiiensis was subjected to chronic, low-dose imidacloprid exposure throughout its larva-to-adult life cycle. Integrating transcriptomics and functional validation was performed. A novel chronic toxicity pathway driven by progressive Ca 2+ -ROS imbalance was identified. Unlike acute-induced rapid Ca 2+ overload and lethal ROS bursts in our prior work, chronic exposure to imidacloprid directly downregulated fatty acid metabolism and Ca 2+ -related genes, alongside GABA/glutamatergic synapse disruption. These eventually caused emergence failure, which was experimentally alleviated by Ca 2+ homeostasis restoration or ROS scavenging. Collectively, the Ca 2+ -ROS-fatty acid axis is confirmed as the core chronic toxic mechanism, emphasizing the neglected ecological risks of sublethal neonicotinoid exposure.