Acute toxic effects of an imidacloprid-based commercial insecticide in Caenorhabditis elegans

Imidacloprid (IMI), a neonicotinoid insecticide, targets postsynaptic nicotinic acetylcholine receptors, resulting in neurotoxicity in insects. Although selective for insects, IMI may have adverse effects on non-target species. This study investigated the acute toxicity of the commercial IMI formulation, Much 600 FS®, in Caenorhabditis elegans. L1-stage nematodes were acutely exposed to IMI at 2.4, 4.8, 7.2, 9.6, and 14.4 g/L concentrations. Developmental inhibition was observed at all concentrations, while significant mortality and reduced brood size occurred at 14.4 g/L. Behavioral assays revealed concentration-dependent decreases in pharyngeal pumping and locomotion. Cholinergic neuronal damage was evident at 7.2 g/L and above, indicating neurotoxicity. Our findings demonstrate that Much 600 FS® exerts toxic effects on C. elegans across developmental, behavioral, reproductive, and neuronal parameters, highlighting its potential risk to non-target organisms, even at sublethal levels.