Canadian Rivers Institute, Department of Biology, University of New Brunswick, Saint John, New Brunswick, Canada.
Ecotoxicol Environ Saf. 2011 Jul;74(5):1363-9. doi: 10.1016/j.ecoenv.2011.04.020. Epub 2011 May 4.
The majority of studies on the toxicity of glyphosate-based herbicides to amphibians have focused on larval life stages exposed in aqueous media. However, adult and juvenile amphibians may also be exposed directly or indirectly to herbicides. The potential for such exposures is of particular interest in the littoral zone surrounding wetlands as this is preferred habitat for many amphibian species. Moreover, it may be argued that potential herbicide effects on juvenile or adult amphibians could have comparatively greater influence on overall recruitment, reproductive potential and thus stability of local populations than effects on larvae. In this experiment, juvenile green frogs (Lithobates clamitans) were exposed to two concentrations (2.16 and 4.27 kg a.e./ha) of a glyphosate-based herbicide formulation (VisionMax®), which were based on typical application scenarios in Canadian forestry. The experimental design employed frogs inhabiting in situ enclosures established at the edge of small naturalized wetlands that were split in half using an impermeable plastic barrier. When analyzed using nominal target application rates, exposure to the glyphosate-based herbicide had no significant effect on survival, body condition, liver somatic index or the observed rate of Batrachochytrium dendrobatidis infection. However, there were marginal trends in both ANOVA analysis and post-hoc regressions regarding B. dendrobatidis infection rates and liver somatic index in relation to measured exposure estimates. Results from this study highlight the importance of field research and the need to include multiple endpoints when examining potential effects of a contaminant on non-target organisms.
大多数关于草甘膦类除草剂对两栖动物毒性的研究都集中在水生介质中暴露的幼虫生命阶段。然而，成体和幼体两栖动物也可能直接或间接地暴露于除草剂之下。这种暴露的可能性在湿地周围的滨水区尤为重要，因为这是许多两栖动物物种的首选栖息地。此外，可以说，与幼虫相比，除草剂对幼体或成体两栖动物的潜在影响可能对当地种群的整体补充、繁殖潜力以及稳定性产生更大的影响。在这项实验中，幼年绿蛙（Lithobates clamitans）暴露于两种浓度（2.16 和 4.27 kg a.e./ha）的草甘膦类除草剂配方（VisionMax®）中，这两种浓度基于加拿大林业中的典型应用场景。实验设计采用了栖息在小自然化湿地边缘的青蛙，这些青蛙被不渗透的塑料屏障分成两半。当使用名义靶标应用率进行分析时，暴露于草甘膦类除草剂对存活率、身体状况、肝体指数或观察到的蛙壶菌感染率没有显著影响。然而，在 ANOVA 分析和事后回归中，关于与测量暴露估计值相关的蛙壶菌感染率和肝体指数都存在边缘趋势。本研究的结果强调了野外研究的重要性，并需要在检查污染物对非目标生物的潜在影响时纳入多个终点。
