Intestinal toxicity and microbiota dysbiosis in zebrafish exposed to spirotetramat

Spirotetramat is a novel, tetrahydrofuran-based broad-spectrum insecticide. It is widely used in global agriculture due to its high insecticidal activity. However, its long-term and extensive use causes environmental accumulation, making its toxicity to non-target organisms a key issue in environmental risk assessments. Previous studies have confirmed that it causes oxidative damage in zebrafish embryos and gonads. The toxic effects and mechanisms of spirotetramat in the zebrafish intestine remain unclear, despite its importance in digestion and absorption, immune defense, and microbiota-host interactions. This study systematically investigated the toxic effects of spirotetramat on zebrafish intestine using multidimensional approaches, including histopathological observation, detection of oxidative stress-related gene expression, and analysis of intestinal microbiota. This study found that gene expression levels of sod, cat, and gpx increased in the 0.08 mg/L group but decreased in the 2 mg/L group, indicating that low concentrations activate the intestinal antioxidant system, while high concentrations cause significant overload. Histopathological analysis revealed intestinal damage, including villus fragmentation and epithelial detachment, in the 2 mg/L treatment group. The increased alkaline phosphatase activity in the 2 mg/L group may be associated with compensatory repair. Microbiota analysis revealed an elevated quantity and diversity of intestinal flora in the treatment groups, with altered abundance of specific bacteria in the 2 mg/L treatment group. Functional prediction of the microbiota suggested that spirotetramat exposure induced changes in metabolic functions. In conclusion, spirotetramat induced intestinal oxidative stress in zebrafish, leading to intestinal barrier damage and microbiota dysbiosis. This study provides a theoretical basis for the comprehensive assessment of spirotetramat's ecological risks.