The impact of hormone signaling on physiology and behavior
The Endocrine System - Hormones
Much of the developmental and behavioral processes of bees is determined by hormones. These chemical messengers are produced in small amounts but have huge effects on their target receptors. Two important hormones found in bees are juvenile hormone (JH) and vitellogenin hormone (VTG).
Juvenile Hormone (JH)
Juvenile hormone is a sesquiterpenoid hormone secreted by the corpora allata in the brain that acts on bees to regulate and control behavioral and physiological development [2]. In larvae and pupae, JH will stimulate development and in adults, JH will signal changes for an individual's role in the hive by regulating the speed in which the bee will become a forager. For the first 15 days of adulthood, JH will increase in concentration as the worker bee transitions to the role of forager, cleaning the hive, caring for the offspring, and other maintenance tasks of the hive. After day 15, a bee will change roles to removing deceased bees from the hive, focus on cooling the hive in warm weather conditions, and guarding and securing the hive from invaders. The more JH a worker bee has during this time, the more aggressive it will become [3].The division of labor based on the time release of a hormone, such as JH, is called temporal polyethism.
Vitellogenin Hormone (VTG)
Vitellogenin hormone is secreted by the liver under the direction of estrogen that stimulates the transition from larvae to pupae. It is found in the hemolymph fluid of females and is stored in fat bodies in the head and abdomen. VTG is important because it counteracts the effects of JH, extending the life of the queen and workers and having a strong impact on the future development of foraging behavior [4]. Low levels of VTG is correlated with earlier foraging of nectar, moderate levels of VTG is correlated with foraging of nectar at normal times in adulthood, and excess levels of VTG is correlated with foraging later in life and for pollen instead of nectar.
JH & VGN Feedback Loop
There is an inverse relationship between juvenile hormone and vitellogenin hormone. In bees, there is a higher amount of juvenile hormone during the larval and adult stages and a decrease during the pupal stage. Conversely, there is a lower amount of vitellogenin during the larval and adult stage but an increase in the pupal stage of development. If there is an imbalance in VGN at any point during any stage of a bee's life, there can be errors in future development and behavior.
Additional Resources
Keller, E. (2018). Nervous system of a honey bee illustration. ArtStation. Retrieved October 26, 2020, from https://www.artstation.com/artwork/nQ20Yr
Wilson-Rich, N., Allin, K., Carreck, N., & Quigley, A. (2014). The Bee A Natural History. Princeton University Press.
Pearce A.N., Huang Z.Y., Breed M.D. (2001) Juvenile hormone and aggression in honey bees, Journal for Insect Physiology. 47, 1243– 1247.
Oliver, Randy (August 2007). "Fat Bees Part 1". American Bee Journal.