Acute toxicity of maneb in the tadpoles of common and green toad

Abstract

Pesticides used in agriculture can have hazardous effects on aquatic organisms, and amphibians are even more threatened than other aquatic vertebrates. Maneb is widely used to control fungal diseases on crops, fruits, and vegetables. The aim of this study was to investigate the acute toxic effects of maneb on the common (Bufo bufo) and green toad (Pseudepidalea viridis) tadpoles. Tadpoles at the development stage 21 were exposed to maneb (0-5 mg L^-1) for 120 h. Maneb LC₅₀ values at hour 120 were 1.966 mg L^-1 for B. bufo and 0.332 mg L^-1 for P. viridis. To the best of our knowledge, these are the first published LC₅₀ findings for the two species. Visceral oedema and tail deformations were observed in both species. We also observed liver necrosis, pronephric tubule deformations, somite deteriorations, and visceral oedema at maneb concentrations ≥0.1 mg L^-1 for B. bufo and ≥0.05 mg L^-1 for P. viridis. Our results show that B. bufo tadpoles have a much higher resilience to maneb than P. viridis tadpoles. This resilience seems to be related to the larger size of the B. bufo tadpoles and their ability to metamorphose faster in adverse conditions. Future research should look into the mechanisms of toxic action of maneb in anurans.