Effects of alpha-cypermethrin and difenoconazole on survival, growth and biomarkers in European green toad tadpoles (<em>Bufotes viridis</em>, Laurenti 1768)

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In recent decades, the decline of amphibian populations has become more pronounced and accelerated, with one of the contributing factors being the excessive use of pesticides. Alpha-cypermethrin, an insecticide, and difenoconazole, a fungicide, are widely employed pesticides globally. To gain a comprehensive understanding of the acute impact of these two pesticides on amphibians, we used European green toad (Bufotes viridis) tadpoles as our model organisms. We assessed mortality and mass as apical endpoints, and examined physiological biomarkers including electron transport system (ETS) activity, catalase activity, and carbonyl protein content. Tadpoles were exposed to varying concentrations of the two pesticides for 48 hours (0.2-10 µg/L for alpha-cypermethrin; 10-100 µg/L for difenoconazole). Our results indicate that the exposure of tadpoles to these pesticides significantly affected their physiology. Mortality was observed exclusively in tadpoles treated with difenoconazole (LC50 = 100.832 µg/L), while a decrease in mass occurred in tadpoles exposed to both pesticides. No significant differences across treatments were found for total ETS activity, catalase activity, or the presence of protein carbonyls. In conclusion, our findings suggest that alpha-cypermethrin at environmentally relevant concentrations poses a risk to European green toad tadpoles, while the effects of difenoconazole are become patent at higher concentrations than those recorded in natural aquatic environments.