Savannah River Ecology Lab, University of Georgia, Aiken, SC 29801, USA.
Savannah River Ecology Lab, University of Georgia, Aiken, SC 29801, USA.
Sci Total Environ. 2019 Jun 1;667:248-254. doi: 10.1016/j.scitotenv.2019.02.314. Epub 2019 Feb 21.
Animals can modulate their own exposure to environmental contaminants through behavioral plasticity such as diet and habitat choice. However, it remains unclear if behavior also has cascading effects on contaminant exposure across multiple generations. In insects, oviposition site selection is an important behavior females can use to modify offspring contaminant exposure risk. In this study, we use the yellow fever mosquito, Aedes aegypti, to test how methylmercury (MeHg) affects oviposition site selection. We found that mosquito larval development rate and survival were negatively affected at MeHg concentrations ≥100 ppb. Adult females not exposed to MeHg as larvae avoided oviposition sites with high MeHg concentrations (>50 ppb), but MeHg exposure at the larval stage significantly affected this oviposition site selection. Specifically, females raised from larvae exposed to non-toxic MeHg levels (i.e., five-50 ppb) showed a significant increase in preference for oviposition sites contaminated with toxic MeHg concentrations (≥500 ppb), compared to unexposed controls. This maladaptive behavioral response could be because, when conditioned with non-toxic MeHg concentrations, MeHg-associated olfactory cues act as a "supernormal" stimulus during oviposition site selection. Importantly, however, this maladaptive behavioral response is eliminated in female mosquitoes raised from larvae exposed to toxic MeHg concentrations (i.e. 100 ppb), and these mosquitoes showed a significant increase in preference for MeHg uncontaminated oviposition sites, compared to unexposed controls. Thus, in mosquitoes, the magnitude of MeHg exposure in one generation can impact MeHg exposure in subsequent generations by altering oviposition site selection behavior. Our results have broad implications for our understanding of how contaminant-mediated behavioral modifications can feedback on contaminant exposure risk across multiple generations, and consequently how behavior can affect the evolutionary trajectory of organisms inhabiting a heterogeneously contaminated environment.
动物可以通过行为可塑性来调节自身暴露于环境污染物的程度，例如饮食和栖息地选择。然而，目前尚不清楚行为是否也会对跨多代的污染物暴露产生级联效应。在昆虫中，产卵地点选择是一种重要的行为，雌性可以利用这种行为来改变后代的污染物暴露风险。在这项研究中，我们使用黄热病蚊子 Aedes aegypti 来测试甲基汞 (MeHg) 如何影响产卵地点的选择。我们发现，当 MeHg 浓度≥100 ppb 时，蚊子幼虫的发育速度和存活率会受到负面影响。在幼虫期未接触 MeHg 的成年雌性会避免在 MeHg 浓度较高（>50 ppb）的产卵地点产卵，但幼虫期暴露于 MeHg 会显著影响这种产卵地点的选择。具体来说，与未暴露的对照组相比，在暴露于无毒 MeHg 水平（即 5-50 ppb）的幼虫中饲养的雌性，对含有有毒 MeHg 浓度（≥500 ppb）的产卵地点的偏好显著增加。这种适应不良的行为反应可能是因为，当用无毒 MeHg 浓度进行条件处理时，MeHg 相关的嗅觉线索在产卵地点选择过程中充当了“超正常”刺激。然而，重要的是，当在幼虫期暴露于有毒 MeHg 浓度（即 100 ppb）的雌性蚊子中，这种适应不良的行为反应会被消除，并且这些蚊子对 MeHg 未污染的产卵地点的偏好显著增加，与未暴露的对照组相比。因此，在蚊子中，一代中的 MeHg 暴露量会通过改变产卵地点选择行为，影响后代的 MeHg 暴露量。我们的研究结果对理解污染物介导的行为改变如何通过在多代之间反馈来影响污染物暴露风险，以及行为如何影响生活在异质污染环境中的生物体的进化轨迹具有广泛的意义。
