Abstract
Glyphosate is the world's most widely used herbicide. The commercial success of this molecule is due to its nonselectivity and its action, which would supposedly target specific biosynthetic pathways found mainly in plants. Multiple studies have however provided evidence for high sensitivity of many nontarget species to glyphosate and/or to formulations (glyphosate mixed with surfactants). This herbicide, found at significant levels in aquatic systems through surface runoffs, impacts life history traits and immune parameters of several aquatic invertebrates' species, including disease‐vector mosquitoes. Mosquitoes, from hatching to emergence, are exposed to aquatic chemical contaminants. In this study, we first compared the toxicity of pure glyphosate to the toxicity of glyphosate‐based formulations for the main vector of avian malaria in Europe, Culex pipiens mosquito. Then we evaluated, for the first time, how field‐realistic dose of glyphosate interacts with larval nutritional stress to alter mosquito life history traits and susceptibility to avian malaria parasite infection. Our results show that exposure of larvae to field‐realistic doses of glyphosate, pure or in formulation, did not affect larval survival rate, adult size, and female fecundity. One of our two experimental blocks showed, however, that exposure to glyphosate decreased development time and reduced mosquito infection probability by malaria parasite. Interestingly, the effect on malaria infection was lost when the larvae were also subjected to a nutritional stress, probably due to a lower ingestion of glyphosate.
Highlights
Glyphosate is the world's most widely used herbicide
Does exposure of larvae to glyphosate influence mosquito life history traits and susceptibility to malaria parasite infections? Second, is the potential effect of glyphosate-based herbicides stronger than glyphosate alone? Third, is there an additive, synergistic, or antagonistic effect between two different stressors, namely glyphosate exposure and food limitation? Experiments were conducted with a natural system consisting of the avian malaria parasite Plasmodium relictum and its vector in the wild, the mosquito Culex pipiens (Pigeault et al, 2015)
We assessed the consequences of larval exposure to pure glyphosate or glyphosate-based herbicide on Culex pipiens mosquito life history traits and susceptibility to avian malaria parasite infection
Summary
Gill, Sethi, Mohan, Datta, & Girdhar, 2018). In addition, glyphosate is mixed with surfactants to improve the performance of this foliar-applied herbicide (surfactants increase the surface area in contact with the vegetation). It has been estimated that less than 0.1% of glyphosate-based herbicides applied to crops reach their specific targets (Nguyen, Nguyen, Hwang, Bui, & Park, 2016). Herbicide and their degradation products are found at significant levels in the environment (Bai & Ogbourne, 2016; Peruzzo, Porta, & Ronco, 2008; Struger et al, 2008) and, in particular, in aquatic systems through surface runoffs (Giesy, Dobson, & Solomon, 2000; Morrissey et al, 2015; Van Bruggen et al, 2018). Does exposure of larvae to glyphosate influence mosquito life history traits and susceptibility to malaria parasite infections? Second, is the potential effect of glyphosate-based herbicides (formulation) stronger than glyphosate alone? Third, is there an additive, synergistic, or antagonistic effect between two different stressors, namely glyphosate exposure and food limitation? Experiments were conducted with a natural system consisting of the avian malaria parasite Plasmodium relictum and its vector in the wild, the mosquito Culex pipiens (Pigeault et al, 2015)
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