Environment and Climate Change Canada, Ecotoxicology and Wildlife Health Division, Ottawa, Ontario, Canada.
Department of Biology, Carleton University, Ottawa, Ontario, Canada.
Environ Pollut. 2021 Sep 1;284:117149. doi: 10.1016/j.envpol.2021.117149. Epub 2021 Apr 15.
Neonicotinoid pesticide use is widespread and highly debated, as evidenced by recent attention received from the public, academics and pesticide regulatory agencies. However, relatively little is known about the physiological effects of neonicotinoid insecticides on aquatic vertebrates. Amphibians (larval stages in particular) are excellent vertebrate bioindicators in aquatic systems due to their risk of exposure and sensitivity to environmental stressors. Previous work with wood frog (Rana sylvatica) tadpoles exposed to formulated products containing thiamethoxam or clothianidin in outdoor mesocosms found significant shifts in leukocyte profiles, suggesting the tadpoles were physiologically stressed. The main objective of the present study was to characterize this stress response further using complementary measures of stress after exposure to clothianidin on northern leopard frogs (Rana pipiens) during their aquatic larval stages. Laboratory static-renewal exposures were conducted over eight weeks with the technical product clothianidin at 0, 0.23, 1, 10 and 100 μg/L, and diquat dibromide at 532 μg/L was used as a positive control. We assessed tadpole leukocyte profiles and measures of oxidative stress as these sub-lethal alterations could affect amphibian fitness. We found changes in several types of leukocytes at 1 and 10 μg/L, suggesting that these tadpoles exhibited signs of mild physiological stress. Clothianidin also induced an oxidative stress response at 0.23, 1 and 100 μg/L. However, we found no differences in survival, growth, development time or hepatosomatic index in frogs exposed to clothianidin. Our study indicates that tadpoles chronically exposed to clothianidin have increased stress responses, but in the absence of concentration-response relationships and effects on whole-organism endpoints, the implications on the overall health and fitness of these changes are unclear.
新烟碱类农药的使用非常广泛，备受争议，这一点可以从公众、学术界和农药监管机构最近对其的关注中得到证实。然而，人们对新烟碱类杀虫剂对水生脊椎动物的生理影响知之甚少。两栖动物（尤其是幼虫阶段）是水生系统中极好的脊椎动物生物指示剂，因为它们面临着暴露于环境胁迫的风险和敏感性。此前，在户外中观模型中，用含有噻虫嗪或噻虫胺的制剂处理林蛙（Rana sylvatica）蝌蚪，发现白细胞谱发生了显著变化，这表明蝌蚪受到了生理压力。本研究的主要目的是在北方豹蛙（Rana pipiens）的水生幼虫阶段暴露于噻虫胺后，使用应激补充措施进一步描述这种应激反应。在 8 周的时间里，采用实验室静态更新法，用噻虫胺技术产品进行暴露，浓度分别为 0、0.23、1、10 和 100μg/L，二溴化百草枯（diguat dibromide）532μg/L 作为阳性对照。我们评估了蝌蚪的白细胞谱和氧化应激指标，因为这些亚致死性变化可能会影响两栖动物的适应能力。我们发现，在 1 和 10μg/L 时，几种类型的白细胞发生了变化，这表明这些蝌蚪表现出轻度生理应激的迹象。在 0.23、1 和 100μg/L 时，噻虫胺还诱导了氧化应激反应。然而，我们发现暴露于噻虫胺的青蛙的存活率、生长、发育时间或肝体比指数没有差异。我们的研究表明，长期暴露于噻虫胺的蝌蚪应激反应增强，但在没有浓度-反应关系和对整体器官终点影响的情况下，这些变化对其整体健康和适应能力的影响尚不清楚。
