Effects of Pydiflumetofen on Bioconcentration, Intestinal Oxidative Stress, and Gut Microbiota in Zebrafish (Danio rerio)

Pydiflumetofen is a novel succinate dehydrogenase inhibitor (SDHI) fungicide frequently detected in aquatic environments, but its effects on the intestinal microecology of zebrafish remain unclear. In this study, zebrafish were exposed to pydiflumetofen at concentrations of 7.33 and 73.3 μg/L for 8 days, and its influence on bioconcentration, oxidative stress, and gut microbiota were assessed. The results show that the bioconcentration factors (BCF8d) were 21.41 and 18.20 L/kg, indicating moderate bioconcentration. Intestinal redox indicators showed time- and concentration-dependent changes. High-concentration exposure was associated with increased oxidative stress indicated by elevated MDA and reduced SOD and GSH levels. β-Diversity revealed significant main effects of concentration and time on gut microbial community structure. Relative abundance analysis suggested opposite trends in Pseudomonadota and Planctomycetota between low- and high-concentration groups and downward trends in Fusobacteriota and Actinomycetota. LEfSe identified exploratory discriminant taxa. However, no family-level difference remained significant after FDR correction. In summary, sublethal pydiflumetofen exposure was associated with internal accumulation, intestinal oxidative stress, and gut microbiota compositional shifts. These results provide multilevel evidence for aquatic hazard characterization of pydiflumetofen under tested conditions.