Fluensulfone induces disruption of core energy metabolism, mitochondrial dysfunction, and reproductive impairment in Eisenia fetida.

Fluensulfone (FSF) is a highly effective nematicide increasingly utilized in agricultural applications. In this study, we exposed earthworms (Eisenia fetida) to environmentally relevant concentrations of FSF and assessed the toxicological responses via an integrated approach combining non-targeted metabolomics, enzyme activity assays, and reverse transcription-quantitative PCR. Exposure to FSF disrupted core energy metabolism by suppressing glycolysis, the tricarboxylic acid cycle, and oxidative phosphorylation. This disruption was reflected by decreased levels of central metabolites (e.g., pyruvate and α-ketoglutarate), inhibition of rate-limiting enzymes (including pyruvate kinase and α-ketoglutarate dehydrogenase), and the downregulation of key mitochondrial genes (CYTB, COX1, and ATP6). These findings collectively point to mitochondrial dysfunction as a central event. Concurrently, the downregulation of reproduction-associated gene ANN and marked declines in cocoon production and juvenile numbers were observed, suggesting a potential connection between systemic energy deficiency and reproductive impairment. Taken together, our study highlights energy metabolism as a sensitive and conserved target, underscoring its relevance to regulatory frameworks for FSF and potentially other next-generation nematicides.