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1. Metabolomic analysis of honey bee ( Apis mellifera L.) response to glyphosate exposure

   https://doi.org/10.1039/D2MO00046F  

   Wang, Bo; Habermehl, Calypso; Jiang, Lin (May 2022, Molecular Omics)

   Glyphosate is among the world's most commonly used herbicides in agriculture and weed control. The use of this agrochemical has unintended consequences on non-target organisms, such as honey bees ( Apis mellifera L. ), the Earth's most prominent insect pollinator. However, detailed understanding of the biological effects in bees in response to sub-lethal glyphosate exposure is still limited. In this study, 1 H NMR-based metabolomics was performed to investigate whether oral exposure to an environmentally realistic concentration (7.12 mg L −1 ) of glyphosate affects the regulation of honey bee metabolites in 2, 5, and 10 days. On Day 2 of glyphosate exposure, the honey bees showed significant downregulation of several essential amino acids, including leucine, lysine, valine, and isoleucine. This phenomenon indicates that glyphosate causes an obvious metabolic perturbation when the honey bees are subjected to the initial caging process. The mid-term (Day 5) results showed negligible metabolite-level perturbation, which indicated the low glyphosate impact on active honeybees. However, the long-term (Day 10) data showed evident separation between the control and experimental groups in the principal component analysis (PCA). This separation is the result of the combinatorial changes of essential amino acids such as threonine, histidine, and methionine, while the non-essential amino acids glutamine and proline as well as the carbohydrate sucrose were all downregulated. In summary, our study demonstrates that although no significant behavioral differences were observed in honey bees under sub-lethal doses of glyphosate, metabolomic level perturbation can be observed under short-term exposure when met with other environmental stressors or long-term exposure. 

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2. Acute exposure to sublethal doses of neonicotinoid insecticides increases heat tolerance in honey bees

   Gonzalez, V.H.; Hranitz, J.M.; McGonigle, M.B.; Manweiler, R.E.; Smith, D.R.; & J.F. Barthell (January 2022, PloS one)

   The European honey bee, Apis mellifera L., is the single most valuable managed pollinator in the world. Poor colony health or unusually high colony losses of managed honey bees result from a myriad of stressors, which are more harmful in combination. Climate change is expected to accentuate the effects of these stressors, but the physiological and behavioral responses of honey bees to elevated temperatures while under simultaneous influence of one or more stressors remain largely unknown. Here we test the hypothesis that exposure to acute, sublethal doses of neonicotinoid insecticides reduce thermal tolerance in honey bees. We administered to bees oral doses of imidacloprid and acetamiprid at 1/5, 1/20, and1/100 of LD50 and measured their heat tolerance 4 h post- feeding, using both dynamic and static protocols. Contrary to our expectations, acute exposure to sublethal doses of both insecticides resulted in higher thermal tolerance and greater survival rates of bees. Bees that ingested the higher doses of insecticides displayed a critical thermal maximum from 2˚C to 5 ˚C greater than that of the control group, and 67%–87% reduction in mortality. Our study suggests a resilience of honey bees to high temperatures when other stressors are present, which is consistent with studies in other insects. We discuss the implications of these results and hypothesize that this compensatory effect is likely due to induction of heat shock proteins by the insecticides, which provides temporary protection from elevated temperatures 

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3. Field-realistic exposure to neonicotinoid and sulfoximine insecticides impairs visual and olfactory learning and memory in Polistes paper wasps

   https://doi.org/10.1242/jeb.246083  

   Corcoran, Fiona E.; Tibbetts, Elizabeth A. (November 2023, Journal of Experimental Biology)

   Exposure to insecticides may contribute to global insect declines due to sublethal insecticide effects on non-target species. Thus far, much research on non-target insecticide effects has focused on neonicotinoids in a few bee species. Much less is known about effects on other insect taxa or newer insecticides, such as sulfoxaflor. Here, we studied the effects of an acute insecticide exposure on both olfactory and visual learning in free-moving Polistes fuscatus paper wasps. Wasps were exposed to a single, field realistic oral dose of either low dose imidacloprid, high dose imidacloprid, or sulfoxaflor. Then, visual and olfactory learning and short-term memory were assessed. We found that acute insecticide exposure influenced performance, as sulfoxaflor and high dose imidacloprid exposed wasps made fewer correct choices than control wasps. Notably, both visual and olfactory performance were similarly impaired. Wasps treated with high dose imidacloprid were also less likely to complete the learning assay than wasps from other treatment groups. Instead, wasps remained stationary and unmoving in the testing area, consistent with imidacloprid interfering with motor control. Finally, wasps treated with sulfoxaflor were more likely to die in the week after treatment than wasps in the other treatment groups. Our findings demonstrate that sublethal, field-realistic dosages of both neonicotinoid and sulfoximine-based insecticides impair wasp learning and short-term memory may have additional effects on survival and motor functioning. Insecticides have broadly detrimental effects on diverse non-target insects that may influence foraging effectiveness, pollination services, and ecosystem function. 

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4. Honey Bees ( Apis mellifera Hymenoptera: Apidae) Preferentially Avoid Sugar Solutions Supplemented with Field-Relevant Concentrations of Hydrogen Peroxide Despite High Tolerance Limits

   https://doi.org/10.1093/jisesa/ieab102  

   Bartlett, Lewis J; Martinez-Mejia, Carlos; Delaplane, Keith S (January 2022, Journal of Insect Science)

   Brunet, Johanne (Ed.)

   Abstract Honey bees (Apis mellifera L. Hymeoptera: Apidae) use hydrogen peroxide (synthesized by excreted glucose oxidase) as an important component of social immunity. However, both tolerance of hydrogen peroxide and the production of glucose oxidase in honey is costly. Hydrogen peroxide may also be encountered by honey bees at high concentrations in nectar while foraging, however despite its presence both in their foraged and stored foods, it is unclear if and how bees monitor concentrations of, and their behavioral responses to, hydrogen peroxide. The costs of glucose oxidase production and the presence of hydrogen peroxide in both nectar and honey suggest hypotheses that honey bees preferentially forage on hydrogen peroxide supplemented feed syrups at certain concentrations, and avoid feed syrups supplemented with hydrogen peroxide at concentrations above some tolerance threshold. We test these hypotheses and find that, counter to expectation, honey bees avoid glucose solutions supplemented with field-relevant hydrogen peroxide concentrations and either avoid or don’t differentiate supplemented sucrose solutions when given choice assays. This is despite honey bees showing high tolerance for hydrogen peroxide in feed solutions, with no elevated mortality until concentrations of hydrogen peroxide exceed 1% (v/v) in solution, with survival apparent even at concentrations up to 10%. The behavioral interaction of honey bees with hydrogen peroxide during both within-colony synthesis in honey and when foraging on nectar therefore likely relies on interactions with other indicator molecules, and maybe constrained evolutionarily in its plasticity, representing a constitutive immune mechanism. 

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5. Inducing ethanol tolerance in free-flying honey bees (Apis mellifera L.)

   https://doi.org/10.46867/ijcp.2021.34.00.03  

   Stephenson, L. L. (January 2021, International journal of comparative psychology)

   Ethanol dependency affects the health of more than 15 million adults in the United States of America. Honey bees have been used as a model for ethanol studies because of similarities in neural structure to vertebrates and their complex social behaviors. This study compares honey bee free-flight visitation to a food source after exposure to ethanol in aqueous sucrose. Individual bees were followed making six attachment visits to a test-station containing 1M sucrose. After attachment, honey bees were randomly assigned to one of five groups: 0%, 2.5%, 5%, 10% EtOH, or a staged increase in ethanol concentrations (2.5%, 5%, 10%). The results indicated that honey bees tolerate up to 2.5% EtOH without avoidance or altered behavior, and up to 5% EtOH without avoidance but with slower trips. At 10% ethanol, attrition was 75% by the 18th return trip. Bees in the staged increase in concentration group were more likely to return than bees that were offered 10% ethanol in sucrose solution after attachment. The results of this study imply that ethanol-induced tolerance to the effects of ethanol can be achieved in honey bees through incremental increase in EtOH but only in terms of attrition. Other measures of foraging efficiency did not show ethanol-induced tolerance. Understanding how ethanol tolerance develops in bees may provide insight into these processes in humans with minimized ethical considerations. 

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