Abstract
Pesticides commonly contaminate the aquatic environments inhabited by mosquito juveniles. However, their role in shaping the mosquito microbiota is not well understood. We hypothesized that environmentally relevant concentrations of atrazine, permethrin and malathion will mediate a shift in the mosquito gut bacterial community structure due to their toxic effect on the aquatic bacterial communities, and reduce mosquito gut bacterial diversity by enriching pesticide-degrading bacterial communities over susceptible taxa. Illumina MiSeq sequencing of the V3-V4 hypervariable regions of the 16 S rRNA gene was used to characterize the microbial communities of larval and adult stages of the two mosquito species and the water samples from microcosms treated with each of the pesticides, separately. Bacterial community composition differed by sample type (larval stage vs. adult stage) and water sampling date (day 3 vs. day 7), but not by pesticide treatment. In larval stages, bacterial OTU richness was highest in samples exposed to malathion, intermediate in permethrin, and lowest in controls. Bacterial richness was significantly higher in larval stages compared to adult stages for all treatments. This study provides a primer for future studies evaluating mosquito microbial responses to exposures to chemical pesticides and the possible implications for mosquito ecology.
Highlights
Pesticides commonly contaminate the aquatic environments inhabited by mosquito juveniles
Illumina sequencing of the V3-V4 hypervariable region of the 16 S rRNA gene amplicons yielded a total of 7,147,541 raw sequence reads from 560 samples (200 Ae. albopictus; 200 Cx. pipiens L.; 160 water samples)
Bacterial OTU richness was highest in larval samples exposed to permethrin, and lowest in adult samples exposed to permethrin (Fig. S1)
Summary
Pesticides commonly contaminate the aquatic environments inhabited by mosquito juveniles. Malathion is commonly used in agricultural pest and public health vector control in the United States, its use for public health vector control has declined significantly due to toxicity concerns and resistance development in some mosquito vector species[8,9,19,20]. Reported physiological and behavioral effects of malathion on mosquito life history traits include prolonged development times, reduced interspecific larval competition, toxicity to larvae, and increased vector competence in some species[22]. In the United States, there has been a steady increase in the usage of pyrethroids in agricultural pest control and public health vector control with permethrin accounting for between 45–60% of all pyrethroids used[24,25] As a result, it is frequently detected in up to 75% of soils and aquatic sediments, albeit at relatively low concentrations (~10 ng/g dry weight). Permethrin concentrations ranging from 0.001–0.002 mg/L have been determined to be effective in routine mosquito control programs[27,28]
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