title: Low doses of neonicotinoid pesticides in food rewards impair short-term olfactory memory in foraging-age honeybees.
abstract: Neonicotinoids are often applied as systemic seed treatments to crops and have reported negative impact on pollinators when they appear in floral nectar and pollen. Recently, we found that bees in a two-choice assay prefer to consume solutions containing field-relevant doses of the neonicotinoid pesticides, imidacloprid (IMD) and thiamethoxam (TMX), to sucrose alone. This suggests that neonicotinoids enhance the rewarding properties of sucrose and that low, acute doses could improve learning and memory in bees. To test this, we trained foraging-age honeybees to learn to associate floral scent with a reward containing nectar-relevant concentrations of IMD and TMX and tested their short (STM) and long-term (LTM) olfactory memories. Contrary to our predictions, we found that none of the solutions enhanced the rate of olfactory learning and some of them impaired it. In particular, the effect of 10 nM IMD was observed by the second conditioning trial and persisted 24 h later. In most other groups, exposure to IMD and TMX affected STM but not LTM. Our data show that negative impacts of low doses of IMD and TMX do not require long-term exposure and suggest that impacts of neonicotinoids on olfaction are greater than their effects on rewarding memories.
authors.affiliation: Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
authors.forename: Geraldine A
authors.initials: GA
authors.lastname: Wright
authors.affiliation: Institute of Neuroscience, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
authors.forename: Samantha
authors.initials: S
authors.lastname: Softley
authors.affiliation: School of Biology, Faculty of Science, Agriculture, and Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Earnshaw
mesh_terms: D000691:Anabasine / Q000494:pharmacology*; D000818:Animals; D001516:Bees / Q000187:drug effects* / Q000502:physiology*; D005247:Feeding Behavior; D007858:Learning / Q000187:drug effects; D008570:Memory, Short-Term / Q000187:drug effects*; D055696:Olfactory Perception / Q000187:drug effects*; D010575:Pesticides / Q000494:pharmacology*; D012201:Reward
chemical_list: D010575:Pesticides; D000691:Anabasine