title: A Locomotor Deficit Induced by Sublethal Doses of Pyrethroid and Neonicotinoid Insecticides in the Honeybee Apis mellifera.
abstract: The toxicity of pesticides used in agriculture towards non-targeted organisms and especially pollinators has recently drawn the attention from a broad scientific community. Increased honeybee mortality observed worldwide certainly contributes to this interest. The potential role of several neurotoxic insecticides in triggering or potentiating honeybee mortality was considered, in particular phenylpyrazoles and neonicotinoids, given that they are widely used and highly toxic for insects. Along with their ability to kill insects at lethal doses, they can compromise survival at sublethal doses by producing subtle deleterious effects. In this study, we compared the bee's locomotor ability, which is crucial for many tasks within the hive (e.g. cleaning brood cells, feeding larvae…), before and after an acute sublethal exposure to one insecticide belonging to the two insecticide classes, fipronil and thiamethoxam. Additionally, we examined the locomotor ability after exposure to pyrethroids, an older chemical insecticide class still widely used and known to be highly toxic to bees as well. Our study focused on young bees (day 1 after emergence) since (i) few studies are available on locomotion at this stage and (ii) in recent years, pesticides have been reported to accumulate in different hive matrices, where young bees undergo their early development. At sublethal doses (SLD48h, i.e. causing no mortality at 48 h), three pyrethroids, namely cypermethrin (2.5 ng/bee), tetramethrin (70 ng/bee), tau-fluvalinate (33 ng/bee) and the neonicotinoid thiamethoxam (3.8 ng/bee) caused a locomotor deficit in honeybees. While the SLD48h of fipronil (a phenylpyrazole, 0.5 ng/bee) had no measurable effect on locomotion, we observed high mortality several days after exposure, an effect that was not observed with the other insecticides. Although locomotor deficits observed in the sublethal range of pyrethroids and thiamethoxam would suggest deleterious effects in the field, the case of fipronil demonstrates that toxicity evaluation requires information on multiple endpoints (e.g. long term survival) to fully address pesticides risks for honeybees. Pyrethroid-induced locomotor deficits are discussed in light of recent advances regarding their mode of action on honeybee ion channels and current structure-function studies.
authors.affiliation: INRA, UR 406 Abeilles et Environnement, 84914, Avignon, France.|UMT, Protection des Abeilles dans l'Environnement, 84914, Avignon, France.
authors.forename: Mercédès
authors.initials: M
authors.lastname: Charreton
authors.affiliation: UMT, Protection des Abeilles dans l'Environnement, 84914, Avignon, France.|ITSAP-Institut de l'abeille, 84914, Avignon, France.|ACTA, 84914, Avignon, France.
authors.forename: Axel
authors.initials: A
authors.lastname: Decourtye
authors.affiliation: INRA, UR 406 Abeilles et Environnement, 84914, Avignon, France.|UMT, Protection des Abeilles dans l'Environnement, 84914, Avignon, France.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Henry
authors.affiliation: INRA, UR 406 Abeilles et Environnement, 84914, Avignon, France.|UMT, Protection des Abeilles dans l'Environnement, 84914, Avignon, France.
authors.forename: Guy
authors.initials: G
authors.lastname: Rodet
authors.affiliation: CNRS, Univ Paris-Sud, IRD, UMR 9191 Evolution, Genomes, Behavior and Ecology, 91198, Gif-sur-Yvette, France.
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Sandoz
authors.affiliation: CNRS, UMR 5237, Université Montpellier 2, Centre de Recherche de Biochimie Macromoléculaire, 34293, Montpellier, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Charnet
authors.affiliation: INRA, UR 406 Abeilles et Environnement, 84914, Avignon, France.|UMT, Protection des Abeilles dans l'Environnement, 84914, Avignon, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Collet
mesh_terms: D000818:Animals; D001516:Bees / Q000378:metabolism; D019791:Guanidine / Q000031:analogs & derivatives* / Q000633:toxicity; D007306:Insecticides / Q000633:toxicity*; D007928:Lethal Dose 50; D009043:Motor Activity / Q000187:drug effects*; D000073943:Neonicotinoids; D009570:Nitriles / Q000633:toxicity; D009574:Nitro Compounds / Q000633:toxicity; D010078:Oxazines / Q000633:toxicity; D011720:Pyrazoles / Q000633:toxicity; D011722:Pyrethrins / Q000633:toxicity*; D000077922:Thiamethoxam; D013844:Thiazoles / Q000633:toxicity
chemical_list: D007306:Insecticides; D000073943:Neonicotinoids; D009570:Nitriles; D009574:Nitro Compounds; D010078:Oxazines; D011720:Pyrazoles; D011722:Pyrethrins; D013844:Thiazoles; C506414:neonicotinoid nitroguanidine; C017160:cypermethrin; C034227:fluvalinate; D000077922:Thiamethoxam; D019791:Guanidine; C082360:fipronil; C009424:tetramethrin