Integration of morphological, physiological, transcriptomic and metabolomic analysis reveals the toxic effects of triadimefon on the earthworm.

Triadimefon is a widely used triazole fungicide whose persistent residues may threaten soil fauna, yet its dose-dependent toxicological mechanisms in earthworms remain insufficiently understood. In this study, morphological, physiological, transcriptomic, and metabolomic analyses were integrated to investigate the toxic effects of triadimefon on the earthworm Eisenia fetida. Triadimefon caused dose-dependent growth inhibition and multi-tissue injury, including epidermal ulceration, muscular disorganization, and intestinal lesions. Ultrastructural observations and oxidative stress analyses further showed cytoplasmic vacuolization, mitochondrial and other intracellular organelle damage, disruption of antioxidant defenses, and increased oxidative DNA damage under high-dose exposure. Transcriptomic profiling revealed extensive molecular reprogramming, with low-dose exposure mainly affecting sensory-motor and locomotory functions together with lipid-related pathways, whereas high-dose exposure strongly suppressed DNA replication- and cell cycle-related processes. Untargeted metabolomics supported these changes and indicated a shift from adaptive metabolic adjustment at low doses to broader metabolic disturbance at high doses, including accumulation of the genotoxic metabolite (E)-2-hexenal. Overall, these findings demonstrate clear dose-dependent host toxicity of triadimefon in earthworms and provide mechanistic insight into how triazole fungicide residues may impair soil fauna.