Effects of Flurochloridone on the Developmental Toxicity in Zebrafish (<i>Danio rerio</i>) Embryo

Flurochloridone (FLC) is a selective herbicide that can cause reproductive toxicity in male rats. However, limited information is available regarding the toxicity of FLC in the developmental stages of aquatic organisms. This study aimed to investigate the effects of FLC exposure during embryonic development and elucidate its potential mechanism of action. Zebrafish embryos were exposed to 6.25, 12.5, 25, and 50 μg/mL FLC for 4-144 hpf. The developmental status of embryos was recorded; the indicators of oxidative stress and embryonic apoptosis were determined. We found that FLC exposure caused severe embryonic malformations, such as pericardial edema, spinal curvature, and growth retardation, accompanied by a decreased hatching and survival rate. After exposure until 144 h postfertilization, the median lethal concentration (LC₅₀) of FLC in zebrafish embryos was 36.9 μg/mL. Subsequently, FLC induced the accumulation of reactive oxygen species and malondialdehyde, enhanced the activity of superoxide dismutase, and activated the Keap1-Nrf2 signaling pathway. Further studies confirmed that FLC can induce apoptosis in zebrafish embryos through the activation of caspase. These results suggest that FLC induced developmental toxicity in zebrafish embryos, which provides new evidence regarding FLC toxicity in aquatic organisms and to assess human health risks.