Abstract
Honeybees show lateral asymmetry in both learning about odors associated with reward and recalling memory of these associations. We have extended this research to show that bees exhibit lateral biases in their initial response to odors: viz., turning toward the source of an odor presented on their right side and turning away from it when presented on their left side. The odors we presented were the main component of the alarm pheromone, isoamyl acetate (IAA), and four floral scents. The significant bias to turn toward IAA odor on the right and away from it on the left is, we argue, a lateralization of the fight-flight response elicited by this pheromone. It contrasts to an absence of any asymmetry in the turning response to an odor of the flowers on which the bees had been feeding prior to testing: to this odor they turned toward when it was presented on either the left or right side. Lemon and orange odors were responded to differently on the left and right sides (toward on the right, away on the left), but no asymmetry was found in responses to rose odor. Our results show that side biases are present even in the initial, orienting response of bees to certain odors.
Highlights
Honeybees have lateralized responses to olfactory stimuli, shown as a bias of better learning to associate an odor with a food reward via use of the right antenna (Letzkus et al, 2006)
To assess approach and withdrawal, it was necessary to allow the bees to move relatively free; i.e., not be restricted as they are when harnessed in holders, the method used previously to demonstrate asymmetry of response to odors in Responses to all three concentrations of isoamyl acetate (IAA) were similar: viz., turning toward the odor when it was presented on the right side and away from it when it was presented on the left side (Figure 1)
For turns toward when presentation of IAA was on the right compared to turning toward when it was presented on the left in the test using 1:300 dilution of FIGURE 1 | Responses to three concentrations of isoamyl acetate
Summary
Honeybees have lateralized responses to olfactory stimuli, shown as a bias of better learning to associate an odor with a food reward via use of the right antenna (Letzkus et al, 2006). In bees trained using both antennae, memory recall of an odor-reward association is better via stimulation of the right antenna in the shorter term after learning and via the left antenna in the longer term after learning (Rogers and Vallortigara, 2008) These asymmetries are matched by left-right asymmetry of neural olfactory coding in the antennal lobes (Rigosi et al, 2015) and asymmetrical gene expression in the left and right sides of the brain (Guo et al, 2016). The attack response includes, initially, abdomen elevation and pumping (Costa et al, 1996), followed by searching and orienting to the source of the odor, and the bee emits high-pitched buzzing and makes body thrusts, which can lead to stinging It increases flight and localization of a moving target (Wagner and Breed, 2000). Our main hypothesis concerned lateralized turning toward versus away responses to the alarm pheromone, which we compared to turning responses to several familiar and unfamiliar floral odors that suppress the fight/flight response (Nouvian et al, 2016)
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