Effects of a commercial formulation of fludioxonil on survival, morphology, and behavior of amphibian embryos and larvae

Fludioxonil is an active principle used as a fungicide to prevent fruit rotting during cold storage. In the present study, we assessed the acute (96 hr) toxicity of the commercial formulation Scholar 23SC to embryos and larvae of the common South American toad (Rhinella arenarum), which inhabits the Alto Valle region in Neuquén and Río Negro, Argentina, an area of intensive fruit production. Scholar 23SC caused lethality in embryos and larvae, with median lethal concentration values of 0.355 mg/L and 1.382 mg/L, respectively. Scholar 23SC caused edema, tail flexure, and growth stunt in the developing embryos, with a median effect concentration value of 0.152 mg/L. In turn, larvae displayed swimming alterations and weakness but no malformations. We reviewed bibliographic data on fludioxonil toxicity to other species to perform a Species Sensitivity Distribution analysis, finding a hazardous concentration-5% (HC5) of 14 µg/L. In turn, from environmental concentration reports, we estimated exceedance probabilities of 5.8% for this HC5 and 13.4% when the lower confidence limit (1.75 µg/L) was used as a conservative criterion. Nevertheless, environmental determinations of fludioxonil concentration in irrigation channels of the Alto Valle region were at approximately the HC5 value. We conclude that Scholar 23SC was more toxic to R. arenarum embryos than larvae, and that the embryonic malformations and the larval behavioral alterations pose a threat to the individuals in a realistic environmental scenario as their performance would be hindered.