Location: Bee Research LaboratoryTitle: Influence of honey bee seasonal phenotype and emerging conditions on diet behavior and susceptibility to imidacloprid
Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2022
Publication Date: 3/14/2022
Publication URL: https://handle.nal.usda.gov/10113/7704036
Citation: Alburaki, M., Madella, S., Vu, P., Corona, M.V. 2022. Influence of honey bee seasonal phenotype and emerging conditions on diet behavior and susceptibility to imidacloprid. Apidologie. 53:12. https://doi.org/10.1007/s13592-022-00922-9.
Interpretive Summary: Honey bee colonies produce two types of seasonal bees: 1- summer bees, which have a short lifespan of few weeks and 2- winter bees whose life can expend up to 6 months. Both seasonal types are important in ensuring the survival and proper function of the colony. Disbalance in the quality and quantity of any of these cohorts could be fatal for the whole colony. Summer and winter bees differ significantly in their physiological characteristics as well as their susceptibility to disease and toxicity. In this study we tested how a widely used neonicotinoid (imidacloprid) affects the diet behavior and survivorship of both seasonal bees. As recent studies indicated, the microbiota seems to play an important role in shielding bees from abiotic stressors. We experimented on two categories of summer bees; emerged in the lab and in-hive. Our results indicated that winter bees are more resilient and significantly stronger than summer bees and preferred to consume syrup laced with imidacloprid. Summer bees showed higher mortality rates than winter bees when exposed to imidacloprid. Being emerged in-hive has affected the diet behavior of summer bees, most probably due to stronger microbiota, and has led to neutrality vis-à-vis imidacloprid versus control-syrup preference. Summer bees emerged in Lab showed clear post-ingestive aversion responses to imidacloprid, constantly avoiding consumption of laced syrup. Overall, despite consuming a lethal concentration of imidacloprid (20PPB), honey bees, particularly winter bees, seem to have a robust detoxification machinery to cope with the toxicological effects of this molecule.
Technical Abstract: Honey bee Apis mellifera L. colonies produce two distinct phenotypes of workers during summer and winter to cope with drastic seasonal variations in climate and food resources. Imidacloprid (IMP) is a neonicotinoid insecticide widely used in agriculture for pest management control. In this study, we investigate the influence of seasonal phenotype and emerging conditions on the diet behavior of bees fed ad libitum two concentrations of IMP. We performed three independent two-choice feeding experiments using summer bees either emerged in the laboratory or in-hive and winter bees. Diet behavior post-ingestive aversion responses to IMP were investigated as well as potential affinity to the physical location and contents of the diets. Caged bees were challenged with a physical rotation of the diet’s location and their susceptibility to 5 and 20 PPB of IMP was tested. From a behavioral standpoint, our results show that winter bees expressed no affinity to the physical location of the diet but rather to its content and strongly favored IMP-tainted syrup at both 5 and 20 PPB. The opposite was recorded for naïve summer bees that emerged in the laboratory, which avoided the tainted syrup at both concentrations, particularly at 20 PPB. Summer bees emerged in-hive, expected to have developed a mature intestinal microbiota through trophallaxis from older bee-mates, were mainly neutral and showed no affinity to the diet location nor its contents. Our results indicate that the physiological changes associated with seasonal phenotype and initial exposure to older mates have important consequences on the bee diet behavior toward pesticides.