Glyphosate is the active ingredient in broad-spectrum herbicide formulations used in agriculture, domestic area and aquatic weed control worldwide. Its market is growing steadily concurrently with the cultivation of glyphosate-tolerant transgenic crops and emergence of weeds less sensitive to glyphosate. Ephemeral and lentic waters near to agricultural lands, representing favorite habitats for amphibian reproduction and early life-stage development, may thus be contaminated by glyphosate based herbicides (GBHs) residues. Previous studies on larval anuran species highlighted increased mortality and growth effects after exposure to different GBHs in comparison to glyphosate itself, mainly because of the surfactants such as polyethoxylated tallow amine present in the formulations.

Nevertheless, these conclusions are not completely fulfilled when the early development, characterized by primary organogenesis events, is considered.

In this study, we compare the embryotoxicity of Roundup^® Power 2.0, a new GBH formulation currently authorized in Italy, with that of technical grade glyphosate using the Frog Embryo Teratogenesis Assay–Xenopus (FETAX). Our results evidenced that glyphosate was not embryolethal and only at the highest concentration (50 mg a.e./L) caused edemas. Conversely, Roundup^® Power 2.0 exhibited a 96 h LC50 of 24.78 mg a.e./L and a 96 h EC50 of 7.8 mg a.e./L. A Teratogenic Index of 3.4 was derived, pointing out the high teratogenic potential of the Roundup^® Power 2.0.

Specific concentration-dependent abnormal phenotypes, such as craniofacial alterations, microphthalmia, narrow eyes and forebrain regionalization defects were evidenced by gross malformation screening and histopathological analysis. These phenotypes are coherent with those evidenced in Xenopus laevis embryos injected with glyphosate, allowing us to hypothesize that the teratogenicity observed for Roundup^® Power 2.0 may be related to the improved efficacy in delivering glyphosate to cells, guaranteed by the specific surfactant formulation. In conclusion, the differences in GBH formulations should be carefully considered by the authorities, since sub-lethal and/or long-term effects (e.g. teratogenicity) can be significantly modulated by the active ingredient salt type and concentration of the adjuvants. Finally, the mechanistic toxicity of glyphosate and GBHs are worthy of further research.

草甘膦是广谱除草剂制剂中的活性成分，用于农业、家庭区域和全球水草控制。随着耐草甘膦转基因作物的种植和对草甘膦不太敏感的杂草的出现，其市场正在稳步增长。因此，农田附近的短暂水域和静水水域是两栖动物繁殖和早期生命阶段发育最喜欢的栖息地，因此可能会受到草甘膦除草剂（GBH）残留物的污染。先前对无尾动物幼虫的研究强调，与草甘膦本身相比，接触不同GBH后死亡率和生长影响有所增加，这主要是因为配方中存在表面活性剂，例如聚乙氧基化牛脂胺。

然而，当考虑到以初级器官发生事件为特征的早期发育时，这些结论并不完全成立。

在这项研究中，我们使用青蛙胚胎致畸试验-非洲爪蟾(FETAX) 比较了 Roundup ^® Power 2.0（一种目前在意大利获得批准的新 GBH 制剂）与工业级草甘膦的胚胎毒性。我们的结果证明，草甘膦不具有胚胎致死性，只有在最高浓度（50 mg ae/L）时才会引起水肿。相反，Roundup ^® Power 2.0 的 96 小时 LC50 为 24.78 mg ae/L，96 小时 EC50 为 7.8 mg ae/L。得出的致畸指数为 3.4，表明农达^® Power 2.0 具有很高的致畸潜力。

通过大体畸形筛查和组织病理学分析证实了特定的浓度依赖性异常表型，例如颅面改变、小眼畸形、窄眼和前脑区域化缺陷。这些表型与注射草甘膦的非洲爪蟾胚胎中所证实的表型一致，使我们能够推测，Roundup ^® Power 2.0 观察到的致畸性可能与特定表面活性剂配方所保证的向细胞输送草甘膦的效率提高有关。总之，当局应仔细考虑 GBH 配方的差异，因为亚致死和/或长期影响（例如致畸性）可以通过活性成分盐类型和佐剂浓度进行显着调节。最后，草甘膦和GBHs的机械毒性值得进一步研究。