Transgenerational interactions between pesticide exposure and warming in a vector mosquito

Abstract

While transgenerational plasticity may buffer ectotherms to warming and pesticides separately, it remains unknown how combined exposure to warming and pesticides in the parental generation shapes the vulnerability to these stressors in the offspring. We studied the transgenerational effects of single and combined exposure to warming (4°C increase) and the pesticide chlorpyrifos on life‐history traits of the vector mosquito Culex pipiens. Parental exposure to a single stressor, either warming or the pesticide, had negative effects on the offspring: parental exposure to both warming and the pesticide resulted in an overall lower offspring survival, and a delayed offspring metamorphosis. Parental exposure to a single stressor did, however, not alter the vulnerability of the offspring to the same stressor in terms of survival. Parental pesticide exposure resulted in larger offspring when the offspring experienced the same stressor as the parents. Within both the parental and offspring generations, warming made the pesticide more toxic in terms of survival. Yet, this synergism disappeared in the offspring of parents exposed to both stressors simultaneously because in this condition, the pesticide was already more lethal at the lower temperature. Our results indicate that transgenerational effects will not increase the ability of this vector species to deal with pesticides in a warming world. Bifactorial transgenerational experiments are crucial to understand the combined impact of warming and pesticides across generations, hence to assess the efficacy of vector control in a warming world.

Whether warming magnifies the toxicity of a pesticide is strongly dependent on the concentration and the null model

“…A temperature increase of 4°C, as expected by 2100 under IPCC (2013) scenario RCP8.5, slightly reduced the survival of C. pipiens. This is consistent with previous results on thermal adaptation in the study species since 20°C corresponds with the mean summer water temperatures of the field sites in Germany where the lab culture originates from (Tran et al, 2018(Tran et al, , 2016. In contrast, in the absence of the pesticide warming had positive (associated with presumably higher fitness values) effects in the survivors by increasing growth rate, total fat content and ETS activity, and decreasing the MDA level.…”

“…Several studies showed that chlorpyrifos is more toxic at higher temperatures in aquatic insects (e.g. Dinh Van et al, 2014;Janssens and Stoks, 2013;Lydy et al, 1999), including the study species (Tran et al, 2018), making it especially relevant to study the impact of CPF under warming.…”

Towards a unified study of multiple stressors: divisions and common goals across research disciplines

“…As a rare example, a synergistic interaction between warming and a pollutant was detected in the mosquito Culex pipiens both in the parents and in the offspring of parents exposed to none or a single stressor. By contrast, an additive effect was present in the offspring of parents exposed to both stressors simultaneously, because in this condition the pesticide was already more lethal at the lower temperature [75]. At the time scale of tens of generations, the evolution of adaptation to a stressor may shape tolerance to subsequent stressors because of pleiotropic effects where the same set of genes contributes to tolerance against different stressors.…”

Development of metal adaptation in a tropical marine zooplankton

“…In general, organisms typically develop increased tolerance to long-term exposures to contaminants as a result of transgenerational plasticity, genetic adaptation, or both [8][9][10][11] . Multiple generational experiments have been applied to test how aquatic animals develop tolerance to stressors, such as metals 11 , polycyclic aromatic hydrocarbons 10 , pesticides 12 , algal toxins 13 , and temperature 14,15 . However, it remains a major challenge to detangle whether phenotypic changes in response to stressors are caused by transgenerational plasticity or from genetic adaptation.…”

“…Adaptations to one stressor often come at the cost of reduced plasticity 16 or reduced capacity to deal with additional stressors 17 . There is increasing evidence that transgenerational plasticity and adaptations to non-contaminant stressors may alter the sensitivity of organisms to a range of contaminants 12,[18][19][20][21] . For example, Dinh et al 22 , using space-for-time substitution, showed that thermal adaptation of aquatic insects results in a higher vulnerability to pesticides.…”