The effects of sublethal doses of imidacloprid and deltamethrin on honeybee foraging time and the brain transcriptome

Colony collapse disorder (CCD) has occurred in the United States since 2006 and has been reported in many countries with varying levels of severity. Although the cause of CCD is multifactorial, pesticide is a major factor that leads to colony collapse. At sublethal doses, pesticide is known to negatively affect honeybee physiological development and behaviour. Previously, we found the insecticides imidacloprid and deltamethrin significantly reduced honeybee dancing and foraging efficiency. In our experiments, the duration of honeybee imbibing food at the feeder declined and the returning period from the feeder to the hive increased in both insecticide groups compared with the control group. As a follow-up, we performed a deep RNA-seq analysis to reveal the gene regulatory mechanisms underlying this altered foraging performance. Genes involved in detoxification were upregulated in both the imidacloprid and the deltamethrin-treatment groups. Gene members in immune pathways, odorant receptors and major royal jelly protein families were significantly downregulated in the treatment groups compared with the controls. This fluctuating gene expression profile shows that multifaceted aspects of honeybee physiology were affected by the two insecticides, which may lead to inaccurate communication and impaired learning and memory. Our findings reveal candidate molecular mechanisms leading to impaired dance performance in honeybees exposed to insecticides.

Automated summary

Colony collapse disorder (CCD) has been occurring in the United States since 2006 and has been reported in many countries. Pesticides, specifically imidacloprid and deltamethrin, have been found to negatively affect honeybee development and behavior, leading to impaired foraging efficiency. Through RNA-seq analysis, we have identified candidate molecular mechanisms underlying the impaired dance performance in honeybees exposed to these insecticides.