Abstract
Glyphosate is the most widely used herbicide in the world with application in agriculture, forestry, industrial weed control, garden and aquatic environments. However, its use is highly controversial for the possible impact on not-target organisms, such as amphibians, which are vanishing at an alarming and rapid rate. Due to the high solubility in water and ionic nature, the glyphosate requires of surfactants to increase activity. In addition, for the control of coca (Erythroxylum coca) and agricultural weeds in Colombia, formulated glyphosate is mixed and sprayed with the adjuvant Cosmo-Flux 411F to increase the penetration and activity of the herbicide. This study evaluates the acute toxic and sublethal effects (embryonic development, tadpole body size, tadpole swimming performance) of the mixture of the formulated glyphosate Roundup Active and Cosmo-Flux 411F to anuran embryos and tadpoles of four Colombian species under 96h laboratory standard tests and microcosms, which are more similar to field conditions as they include soil, sand and macrophytes. In the laboratory, embryos and tadpoles of Engystomops pustulosus were the most tolerant (LC50 = 3904 microg a.e./L; LC50=2 799 pg a.e./L, respectively), while embryos and tadpoles of Hypsiboas crepitans (LC50=2 203 microg a.e./L; LC50=1424 microgg a.e./L, respectively) were the most sensitive. R. humboldti and R. marina presented an intermediate toxicity. Embryos were significantly more tolerant to the mixture than tadpoles, which could be likely attributed to the exclusion of chemicals by the embryonic membranes and the lack of organs, such as gills, which are sensitive to surfactants. Sublethal effects were observed for the tadpole body size, but not for the embryonic development and tadpole swimming performance. In microcosms, no toxicity (LC50 could not be estimated), or sublethal responses were observed at concentrations up to fourfold (14.76 kg glyphosate a.e./ha) the highest field application rate of 3.69 kg glyphosate a.e./ha. Thus, toxicity was less in the microcosms than in laboratory tests, which may be attributed to the presence of sediments and organic matter which rapidly adsorb glyphosate and surfactants such as POEA. It is concluded that the mixture of glyphosate (Roundup Active) and Cosmo-Flux*411F, as used in the field, has a negligible toxic effect to embryos and tadpoles of the species tested in this study.
Highlights
Glyphosate is the active ingredient of several herbicide formulations, which contains surfactants such as the ethoxylated tallowamine (POEA) that vary in concentration and may have a greater toxicity than glyphosate itself (Bradberry, Proudfoot, & Vale, 2004)
The fifth centile of the toxicity distribution was 883μg a.e./L, indicating that 95% of Colombian species are within the toxicity range reported to glyphosate formulations
There were significant differences between concentrations (0, 325, 750, 1 500μg a.e./L) for all four morphometric measures (TL, head width (HW), corporal length (CL), tail length (tL)) (ANOVA, p
Summary
Triana, Montes and Bernal (2013), on the other hand, evaluated the effect of glyphosate (Roundup® Active) to anuran embryos of four Colombian species, and showed that it was highly toxic in laboratory experiments but less in microcosm conditions. Despite these data, there is no still information about the toxicity of the combined glyphosate and Cosmo-Flux®411F, as sprayed in field, to embryos from Colombian anurans. This study was conducted to evaluate the acute toxicity and sublethal effects (embryonic development, tadpole body size, tadpole swimming performance) of the mixture of Roundup® Active and the adjuvant Cosmo-Flux®411F to embryos and tadpoles of four Colombian anuran species. All solutions were prepared with the same dechlorinated tap water used to raise the embryos and tadpoles
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