Honey bees (Apis mellifera) are pretty intelligent little creatures, and are a good model for studying associated learning3. Honey bees are quite capable of associated learning, but sometimes not so capable of aversive learning2. In her seminar at University of Sydney, Dr Vanina Vergoz (from University of Sydney) explained the role of the Queen Mandibular Pheromone (QMP) in preventing aversive learning in honey bees in order to attract worker bees and literally brainwash them to complete certain tasks and have certain behaviours.
Associated and aversive learning
Associated learning refers to an individual responding to a particular stimulus, such as a cat associating food with the opening of a cupboard – the cat runs towards the cupboard to receive its reward. If on the other hand, the opening of the cupboard always triggers a spray with water, will the cat still eagerly come? Probably not. This is aversive learning, whereby an individual will avoid the stimulus as it is seen as a type of punishment.
Associated learning in honey bees
Many studies on honey bees in the past have focussed on appetitive learning3 – this involves presenting an odour to a bee and then providing it with sucrose2. The bee associates the specific odour with the reward, and hence when exposed to the odour, the bee automatically extends its proboscis to receive the reward – a proboscis extension reflex (PER)2,3.
This method can also be used to study aversive learning, which was first explored in honey bees by Vergoz et al. (2007). As explained by Dr Vergoz, instead of rewarding the bees after presenting an odour, the bees receive a mild electric shock. This initiates a sting extension reflex (SER), which is a defensive response in honey bees3. However, in the presence of the Queen Mandibular Pheromone (QMP), bees were unable to make an association between an odour and an electric shock, but could still associate an odour with a reward2. Therefore, in the presence of the queen, aversive learning is typically not seen in honey bees. As questioned by Dr Vergoz, is the queen trying to supress young worker bees from forming an aversion to her? Before answering this, we should look into what QMP actually is.
Experiment testing honey bee sting extension reflex (SER). Source: Vergoz et al. (2007)
Queen Mandibular Pheromone (QMP)
Honey bees are sophisticated in their communication – over 50 chemicals are used by honey bees to communicate within the colony1. By communicating with her colony, the queen can control the behaviour and physiology of those in her nest – a form of organisation1. One substance particularly useful for this control is QMP1.
The production of QMP by the queen allows her presence to be known within the colony4, as it entices young workers to tend to her by feeding and grooming her1,4. QMP is collected by these young workers and spread throughout the colony, which prevents the development of ovaries of workers within the colony and hence preventing other workers from reproducing4.
Worker bees tending to their queen. Source: Beggs et al. (2007, p. 2461)
- The role of dopamine
Dopamine is a compound that is required for aversive learning2,4 and can have a large impact on the learning ability of honey bees3. Dopamine levels can actually decline in the presence of QMP, leading to a suppression of aversive learning2. For example, Beggs et al. (2007) found that bees that were exposed to QMP had significantly lower levels of dopamine in the brain compared to those not exposed to QMP. In addition, Vergoz et al. (2007) found that those bees that were exposed to QMP did not develop aversive learning – it impaired their learning ability.
Why block aversive learning?
It is evident that the queen does advantage from blocking aversive learning, as the workers groom her, feed her and take care of her2, increasing her survival4. Vergoz et al. (2007) proposed that the workers actually don’t enjoy attending to the queen. If aversive behaviour is not blocked, there can be huge ramifications for the queen, such as repelling workers, causing aggression, and possibly leading to the demise of the queen4. So, a worker that doesn’t establish an aversive memory won’t be able to establish a relationship between QMP and negative side effects4. The workers will therefore continue tending to the queen4.
Even though the study of neuroscience solely focuses on the brain2, Dr Vergoz stated that the role of QMP affecting worker behaviour and reproduction shows that we need to start looking at the individuals as a whole. New research suggests that the gut and ovaries can influence behaviour2. This emphasises the need to look past the individual components and to a more holistic approach2.
- Beggs, K. T., Glendining, K. A., Marechal, N. M., Vergoz, V., Nakamura, I., Slessor, K. N., & Mercer, A. R. (2007). Queen pheromone modulates brain dopamine function in worker honey bees. Proceedings of the National Academy of Sciences, 104(7), 2460-2464. doi:10.1073/pnas.0608224104
- Vergoz, V. (2014, March 28). The queen, her pheromone and reproductive hegemony in honey bees. School of Biological Science Seminar Series. Conducted from University of Sydney, Camperdown, NSW.
- Vergoz, V., Roussel, E., Sandoz, J. C., & Giurfa, M. (2007). Aversive learning in honeybees revealed by the olfactory conditioning of the sting extension reflex. PLoS One, 2(3), e288. doi: 10.1371/journal.pone.0000288
- Vergoz, V., Schreurs, H. A., & Mercer, A. R. (2007). Queen pheromone blocks aversive learning in young worker bees. Science, 317(5836), 384-386. doi: 10.1126/science.1142448