skip to main content

This content will become publicly available on January 1, 2023

Title: Honey Bees ( Apis mellifera Hymenoptera: Apidae) Preferentially Avoid Sugar Solutions Supplemented with Field-Relevant Concentrations of Hydrogen Peroxide Despite High Tolerance Limits
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 more » 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. « less
; ;
Brunet, Johanne
Award ID(s):
Publication Date:
Journal Name:
Journal of Insect Science
Sponsoring Org:
National Science Foundation
More Like this
  1. Bloch, Guy (Ed.)
    Abstract Honey bees, as many species of social insects, display a division of labor among colony members based on behavioral specializations related to age. Adult worker honey bees perform a series of tasks in the hive when they are young (such as brood care or nursing) and at ca. 2–3 wk of age, shift to foraging for nectar and pollen outside the hive. The transition to foraging involves changes in metabolism and neuroendocrine activities. These changes are associated with a suite of developmental genes. It was recently demonstrated that antibiotics influence behavioral development by accelerating or delaying the onset ofmore »foraging depending on timing of antibiotic exposure. To understand the mechanisms of these changes, we conducted a study on the effects of antibiotics on expression of candidate genes known to regulate behavioral development. We demonstrate a delay in the typical changes in gene expression over the lifetime of the individuals that were exposed to antibiotics during immature stage and adulthood. Additionally, we show an acceleration in the typical changes in gene expression on individuals that were expose to antibiotics only during immature stage. These results show that timing of antibiotic exposure alter the typical regulation of behavioral development by metabolic and neuroendocrine processes.« less
  2. Abstract

    Hummingbirds utilize visual cues to locate flowers, but little is known about the role olfaction plays in nectar foraging despite observations that hummingbirds avoid resources occupied by certain insects. We investigated the behavioral responses of both wild and captive hummingbirds to olfactory cues of hymenopteran floral visitors, including native wood ants (Formica francoeuri), invasive Argentine ants (Linepithema humile), and European honeybees (Apis mellifera). We demonstrate for the first time that hummingbirds use olfaction to make foraging decisions when presented with insect-derived chemical cues under field and aviary conditions. Both wild and captive hummingbirds avoided foraging on feeders with defensive chemicalsmore »ofF. francoeuriand aggregation pheromones ofL. humile, but showed no response to honeybee cuticular hydrocarbons. Our experiments demonstrate the importance of olfaction in shaping hummingbird foraging decisions.

    Significance statement

    Recent reviews reveal that avian olfaction is not just limited to vultures and a few taxa. We demonstrate that a very charismatic group, hummingbirds, avoid defensive and aggregatory chemical cues from insects present at nectar resources. Olfactory cues can provide critical information about the presence and potential threat of insect floral visitors. This study raises new questions about the underrated importance of olfaction in avian foraging and specifically, hummingbird foraging.

    « less
  3. 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%).more »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.« less
  4. Nearly 90% of flowering plants depend on animals for reproduction. One of the main rewards plants offer to pollinators for visitation is nectar. Nesocodon mauritianus (Campanulaceae) produces a blood-red nectar that has been proposed to serve as a visual attractant for pollinator visitation. Here, we show that the nectar’s red color is derived from a previously undescribed alkaloid termed nesocodin. The first nectar produced is acidic and pale yellow in color, but slowly becomes alkaline before taking on its characteristic red color. Three enzymes secreted into the nectar are either necessary or sufficient for pigment production, including a carbonic anhydrasemore »that increases nectar pH, an aryl-alcohol oxidase that produces a pigment precursor, and a ferritin-like catalase that protects the pigment from degradation by hydrogen peroxide. Our findings demonstrate how these three enzymatic activities allow for the condensation of sinapaldehyde and proline to form a pigment with a stable imine bond. We subsequently verified that synthetic nesocodin is indeed attractive to Phelsuma geckos, the most likely pollinators of Nesocodon . We also identify nesocodin in the red nectar of the distantly related and hummingbird-visited Jaltomata herrerae and provide molecular evidence for convergent evolution of this trait. This work cumulatively identifies a convergently evolved trait in two vertebrate-pollinated species, suggesting that the red pigment is selectively favored and that only a limited number of compounds are likely to underlie this type of adaptation.« less
  5. Abstract. The mechanisms of molecular halogen production from frozen saline surfacesremain incompletely understood, limiting our ability to predict atmosphericoxidation and composition in polar regions. In this laboratory study,condensed-phase hydroxyl radicals (OH) were photochemically generated infrozen saltwater solutions that mimicked the ionic composition of oceanwater. These hydroxyl radicals were found to oxidize Cl−, Br−, andI−, leading to the release of Cl2, Br2, I2, and IBr. Atmoderately acidic pH (buffered between 4.5 and 4.8), irradiation of icecontaining OH precursors (either of hydrogen peroxide or nitrite ion)produced elevated amounts of I2. Subsequent addition of O3produced additional I2, as well as small amounts ofmore »Br2. At lowerpH (1.7–2.2) and in the presence of an OH precursor, rapid dark conversionof I− to I2 occurred from reactions with hydrogen peroxide ornitrite, followed by substantial photochemical production of Br2 uponirradiation. Exposure to O3 under these low pH conditions alsoincreased production of Br2 and I2; this likely results fromdirect O3 reactions with halides, as well as the production ofgas-phase HOBr and HOI that subsequently diffuse to frozen solution to reactwith Br− and I−. Photochemical production of Cl2 was onlyobserved when the irradiated sample was composed of high-purity NaCl andhydrogen peroxide (acting as the OH precursor) at pH = 1.8. Thoughcondensed-phase OH was shown to produce Cl2 in this study, kineticscalculations suggest that heterogeneous recycling chemistry may be equallyor more important for Cl2 production in the Arctic atmosphere. Thecondensed-phase OH-mediated halogen production mechanisms demonstrated hereare consistent with those proposed from recent Arctic field observations ofmolecular halogen production from snowpacks. These reactions, even if slow,may be important for providing seed halogens to the Arctic atmosphere. Ourresults suggest the observed molecular halogen products are dependent on therelative concentrations of halides at the ice surface, as we only observewhat diffuses to the air–surface interface.« less