Octopamine and tyramine modulate the thermoregulatory fanning response in honey bees (Apis mellifera L.)

Authors: COOK, CHELSEA - Arizona State University; Brent, Colin; BREED, MICHAEL - University Of Colorado

Submitted to: Journal of Experimental Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2017
Publication Date: 6/10/2017
Publication URL: http://handle.nal.usda.gov/10113/5700726
Citation: Cook, C.N., Brent, C.S., Breed, M.D. 2017. Octopamine and tyramine modulate the thermoregulatory fanning response in honey bees (Apis mellifera L.). Journal of Experimental Biology. 220:1925-1930.

Interpretive Summary: Neurotransmitters known as biogenic amines regulate the physiological changes in an individual that lead to a particular behaviors. Changes in biogenic amine levels can be caused by shifts in environmental conditions, encouraging animals to behave in ways that are best suited to those conditions. Here, we examined how changes in biogenic amines can regulate fanning in honey bees, a behavior necessary to keep a bee hive cool during the summer. We found that the concentrations of two biogenic amines, octopamine and tyramine, are lower in active fanners than in non-fanners. Additionally, feeding these biogenic amines to the bees causes a change in the likelihood of fanning. This is the first evidence that fanning behavior is influenced by these two biogenic amines. However, honey bees that were unlikely to engage in fanning behavior had neurotransmitter levels similar to those that did fan after being exposed to heat. This result suggests that each member of a honey bee colony has a different response threshold which determines the specific behaviors they are likely to exhibit. This variation between individual would contribute to the observed development of different behavioral castes in a colony. These findings provide key insights that contribute to better understanding the behaviors crucial to maintaining healthy colony conditions for these key pollinators.

Technical Abstract: Biogenic amines regulate the proximate mechanisms underlying most behavior, including those that contribute to the overall success of complex societies. For honey bees one critical set of behaviors contributing to the welfare of a colony are involved with nest thermoregulation. Worker honey bees cool the colony by performing a fanning behavior, the expression of which is largely influenced by response thresholds that are influenced by the social environment. Here, we examined how changes in biogenic amines affect this group-performed thermoregulatory fanning behavior in honeybees. Concentrations of two biogenic amines, octopamine and tyramine, are significantly lower in active fanners than in non-fanners. Direct feeding of these biogenic amines induced a decrease in fanning responses, but only when both amines were included in the treatment. This is the first evidence that fanning behavior is influenced by these two biogenic amines, and this result is consistent with their role in regulating locomotor activity in other insects. Individual variation in amine expression also provides a mechanistic link that helps to explain how this group behavior might be coordinated within a colony.