Sunflower aroma detection by the honeybee

Journal of Chemical Ecology, 1994

A n~wel technique for the simultaneous monitoring of etectroantennogram (EAG) and conditioned proboscis extension (CPE'~ responses of honey bees to the effluent from a gas chromatograph (GC) was developed to locate biologically active components in blends of plant volatiles and to investigate odor recognition at the peripheral and behavioral levels. A six-component mixture, comprising compounds previously identified as oilseed rape floral volatiles, was used as the stimulus. Standard CPE and EAG recordings were done as a reference. EAG responses were elicited from unconditioned bees by all the components presented either in the coupled or the standard mode, Conditioned bees gave larger EAG responses than unconditioned bees, suggesting that antennal sensitivity is enhanced by conditioning. At the behavioral level, in both the standard and the coupled modes, only conditioned bees showed the proboscis extension response, with the majority of individuals responding to linalool, 2-phenylethanol. and benzyl alcohol,

Entomologia Experimentalis et Applicata, 1997

Honeybees (Apis mellifera L.) were individually subjected to a classical conditioning procedure in order to obtain an olfactory conditioned proboscis extension response. To relate the behavioural response directly to antennal detection abilities, a technique was developped for coupling proboscis extension responses and electroantennogram recordings, with the stimulation being provided by the effluent of a gas chromatograph (GC). Bees were conditioned with a six-component mixture being part of oilseed rape (Brassica napus L.) floral volatiles, and tested with the individual components separated by GC. Responses of the conditioned bees were compared to those of unconditioned bees. No behavioural response was obtained in the control group, neither to the individual components nor to the mixture. Conditioning induced behavioural responses for three components, and an increase of electroantennogram responses for all components. A second experiment was conducted with an air entrainment extract of oilseed rape flower volatiles. Behavioural responses of conditioned and unconditioned bees were recorded. Responses obtained from conditioned bees tested with the air entrainment extract showed six groups of behaviourally active GC peaks. Unconditioned bees showed the same pattern of responses but at a lower level. The coupled technique described here appears to be a reliable tool for locating active components in a synthetic as well as in a natural mixture of floral volatiles. The effects of conditioning on odour discrimination and on its sensory correlates are discussed.

Chemical Senses, 1997

The coupled gas chromatography-proboscis extension assay technique was used on restrained worker bees to study responses to components of an extract of oilseed rape floral volatiles. Bees were stimulated with the effluent from the gas chromatograph after either paired or unpaired conditioning to the extract, or after a control treatment.

PLOS ONE, 2023

Organic volatiles produced by fruits can result in overestimation of sweetness by humans, but it is unknown if a comparable phenomenon occurs in other species. Honey bees collect nectar of varying sweetness at different flowering plants. Bees discriminate sugar concentration and generally prefer higher concentrations; they encounter floral volatiles as they collect nectar, suggesting that they, like humans, could be susceptible to sweetness enhancement by odorant. In this study, limonene, linalool, geraniol, and 6-methyl-5-hepten-2-ol were tested for their ability to alter behaviors related to perception of sweetness by honey bees. Honey bees were tested in the laboratory using proboscis extension responsebased assays and in the field using feeder-based assays. In the laboratory assays, 6methyl-5-hepten-2-ol and geraniol, but neither linalool nor limonene, significantly increased responses to low concentrations of sucrose compared with no odorant conditions in 15-day and 25-day-old adult worker honey bees, but not in 35-day-old bees. Limonene reduced responding in 15-day-old bees, but not in the older bees. There was no odorant-based difference in performance in field assays comparing geraniol and limonene with a no odorant control. The interaction of the tested plant volatiles with sucrose concentration revealed in laboratory testing is therefore unlikely to be a major determinant of nectar choice by honey bees foraging under natural conditions. Because geraniol is a component of honey bee Nasonov gland pheromone as well as a floral volatile, its impact on responses in the laboratory may reflect conveyance of different information than the other odorants tested.

Journal of Asia-Pacific Entomology, 2016

Morphological and peripheral olfactory responses of antennal chemosensilla of Apis cerana indica, worker honeybee, to commonly occurring plant volatiles were recorded using SEM and EAG techniques, respectively. The antennae of A. cerana indica reveal the predominance of olfactory sensilla besides gustatory and mechanoreceptor cells. Ten different types of olfactory sensilla including sensilla basiconica, placodea type A and B, chaetica, coeloconica, coelocapitula, trichodea type A, B, C and D were reported. Of these, trichodea B and placodea A types were reported to be maximum. Responses to 47 commonly occurring plant volatiles (including 10 aromatic, 12 aliphatic, 04 green leaf volatile, 10 hydrocarbon monoterpene, 08 oxygenated monoterpenes and 03 sesquiterpenes compounds) were shown to elicit the response. Normalized EAG response, relative to the standard 1-hexanol, reveal significant differences between the chemicals and were concentration dependent. At 0.1 mg/mL dose, the largest amplitude was obtained with p-cymene (119.74 ± 6.94) followed by cinnamaldehyde (97.07 ± 4.94) and veratrol (92.99 ± 7.82). Furthermore, at 1.0 mg/mL, maximum stimulation was reported with cinnamaldehyde (92.02 ± 4.26) followed by phenethyl alcohol (86.02 ± 2.63), benzyl alcohol (70.53 ± 2.47), 2-heptanone (67.71 ± 5.02) and 1-heptanol (67.56 ± 2.8). Again, amplitude of the response was found to be maximum with cinnamaldehyde (115.59 ± 6.73) followed by 1-heptanol (105.69 ± 2.45) and citral (100.78 ± 4.93) at 5.0 mg/mL, whereas, at 10.0 mg/mL, phenethyl alcohol (93.45 ± 1.87) and 2-heptanone (93.14 ± 1.85) showed highest stimulation followed by 2-pentanone (92.22 ± 0.43). These documentations provide valuable information regarding how diversity in chemoreceptive antennal sensilla reveals better ability to sense a diversity of odors that are important cues to help honeybee distinguish among species of various flowering plants.

Journal of Chemical Ecology, 2005

Many bees are oligolectic and collect pollen for their larvae only from one particular plant family or genus. Here, we identified flower scent compounds of two Salix species important for the attraction of the oligolectic bee Andrena vaga, which collects pollen only from Salix. Flower scent was collected by using dynamic-headspace methods from Salix caprea and S. atrocinerea, and the samples were subsequently analyzed by coupled gas chromatographic-electroantennographic detection (GC-EAD) to detect possible attractants of A. vaga. EAD active compounds were identified by gas chromatography coupled to mass spectrometry. Both Salix species had relatively similar scent profiles, and the antennae of male and female bees responded to at least 16 compounds, among them different benzenoids as well as oxygenated monoterpenoids and sesquiterpenoids. The strongest antennal responses were triggered by 1,4-dimethoxybenzene, and in field bioassays, this benzenoid attracted females of A. vaga at the beginning of its flight period, but not at the end.

Apidologie, 2005

Journal of chemical …, 1997

Volatiles from oilseed rape, Brassica napus, flowers were sampled by air entrainment and their relevance to the natural odor profile of the flowers was confirmed by conditioned proboscis extension (CPE) assays with honeybee. Apis mellifera L., foragers. Coupled gas chromatography (GC)-CPE analysis of the air entrainment samples was used to locate key compounds involved in the recognition of B. napus flowers, and the compounds were then identified using coupled gas chromatography-mass spectrometry and comparison with authentic samples. Six regions of the gas chromatograms elicited CPE responses from bees previously conditioned to the total extract, and from these areas 16 compounds were identified that elicited CPE activity from conditioned bees when tested with synthetic samples. Eight of the 16, a-pinene, phenylacetaldehyde, p-cymene, a-terpinene, linalool, 2-phenylethanol, (E,£)-a-farnesene, and 3-carene, gave the highest responses. When the bees were conditioned to the total extract of flower volatiles, a mixture of the eight components elicited responses from 83% of the individuals, suggesting that the eight-component mixture accounted for a major part of the CPE activity of the total extract. In addition, a mixture of the three most active compounds, phenylacetaldehyde, linalool, and (£,£,)-a-farnesene, *To whom correspondence should be addressed. 1715 0098-033l/97/0700-l7l5$12.50/0 © 1997 Plenum Publishing Corporation to the eight-component mixture. Thus, these three compounds appear to play a key role in the recognition of the eight component mixture and, by inference, of oilseed rape flowers.

Scientific Reports, 2021

The increasing demand on pollination services leads food industry to consider new strategies for management of pollinators to improve their efficiency in agroecosystems. Recently, it was demonstrated that feeding beehives food scented with an odorant mixture mimicking the floral scent of a crop (sunflower mimic, SM) enhanced foraging activity and improved recruitment to the target inflorescences, which led to higher density of bees on the crop and significantly increased yields. Besides, the oral administration of nonsugar compounds (NSC) naturally found in nectars (caffeine and arginine) improved short and long-term olfactory memory retention in conditioned bees under laboratory conditions. To test the effect of offering of SM-scented food supplemented with NSC on honeybees pollinating sunflower for hybrid seed production, in a commercial plantation we fed colonies SM-scented food (control), and SM-scented food supplemented with either caffeine, arginine, or a mixture of both, in field realistic concentrations. Their foraging activity was assessed at the hive and on the crop up to 90 h after treatment, and sunflower yield was estimated prior to harvest. Our field results show that SM + Mix-treated colonies exhibited the highest incoming rates and densities on the crop. Additionally, overall seed mass was significantly higher by 20% on inflorescences close to these colonies than control colonies. Such results suggest that combined NSC potentiate olfactory learning of a mimic floral odor inside the hive, promoting faster colony-level foraging responses and increasing crop production.

Journal of chemical …, 2000

Complex odor recognition in the honeybee was investigated using two behavioral assays: (1) the conditioning of the proboscis extension (CPE) with restrained individuals, and (2) the observation of foragers visiting an artificial feeder in a flight room. Nine compounds, previously identified as oilseed rape flower volatiles, were tested either individually or in mixtures. Different sets of experiments were done to determine: (1) the acquisition rate of the nine compounds in the CPE assay, and (2) the discrimination of the individual compounds after conditioning to a mixture, using the CPE assay and free-flying foragers. After conditioning to a complex mixture, honeybees established a hierarchy among the components, with some of them accounting for a major part of the behavioral activity of the mixture. Both behavioral assays led to the same classification of compounds, indicating good agreement between discriminating abilities of restrained individuals and of a population of foragers. The key compounds for recognition of these mixtures were those that were well learned when presented individually. However, the recognition of some compounds was affected by the other components of the mixture, with the activity of some compounds being either enhanced or reduced.