Impacts of Imidacloprid and Flupyradifurone Insecticides on the Gut Microbiota of Bombus terrestris

Qingchao Zhang,Xiaofei Wang,Qinglin Wang,Yifan Zhai,Hao Zheng

doi:10.3390/agriculture12030389

Abstract

Bumblebees are important pollinators for crops and wild flowering plants. Various pesticides have threatened the abundance and diversity of bumblebees. In addition to direct sublethal effects, pesticides may alter the gut microbial communities of bees. Imidacloprid and flupyradifurone insecticides both bind to the nicotinic acetylcholine receptor. However, the latter was assumed to be harmless for honeybees and can even be applied to flowering crops. In this study, we assessed the impacts of these two pesticides on queenless microcolonies and the gut microbiota of Bombus terrestris. We found that 10 μg/L imidacloprid significantly impeded syrup consumption, and postponed the egg-laying period, larvae, and pupae development. It decreased the relative abundance of the bumblebee-specific symbionts, Apibacter and Lactobacillus Firm-5. On the contrary, 10 μg/L flupyradifurone did not reduce syrup consumption, block larvae and pupae development in bumblebees. Although no significant phenotypes were observed, PICRUST revealed that flupyradifurone suppressed pathways, involving carbohydrate metabolism, nucleotide metabolism, translation, and membrane transport. Our findings suggest the appropriate use of this new pesticide may be considered safe for bumblebees, but the underlying mechanism warrants further investigation.

Highlights

Since the pollen from imidacloprid-treated crops generally contains residues of neonicotinoids, ranging from 1 μg/kg to 3 μg/kg [42–44], we set the concentration of imidacloprid and flupyradifurone at 0.1, 1, and 10 μg/L to investigate whether exposure to insecticides affects bumblebee performance over similar levels of field-realistic exposure
There was no significant difference in syrup consumption during the first week (Figure 2A)
10μg/L imidacloprid-treated B. terrestris delayed the time of nest construction and the initiation of egg-laying and reduced larval production by 43% [49,50]

Summary

Introduction

Bumblebees (Bombus genus) play a vital role as efficient pollinators in agricultural and natural systems. Several bumblebee species, such as Bombus impatiens and Bombus terrestris, have been domesticated for commercial pollination service, for both glasshouse and open-field crops [1]. Over recent years, populations of bumblebees have continued to decline, on a global scale [2]. Multiple factors may contribute to the decline of the bumblebee population, such as habitat loss, parasites and diseases, invasive species, and pesticide exposure [3–7]. Both laboratory and field studies demonstrated the negative impacts of pesticides on bumblebee reproduction, colony development, and behavior [8–10]. Assessments on the risks of the exposure of bumblebees to insecticide compounds are necessary

Results

Discussion

Conclusion