Honey bee queens control their offspring with chemicals (pheromones), but how these chemicals work has largely remained a mystery until now.

Professor Alison Mercer and her research team in the Department of Zoology at the University of Otago have discovered that exposing young worker bees to queen pheromone alters the chemistry of the honey bee brain.

This study provides a direct link between changes in brain biochemistry and complex behaviour.

In a study published earlier this year in Proceedings of the National Academy of Sciences, Kyle Beggs, Kelly Glendining, Nicola Marechal, Vanina Vergoz, Ikumi Nakamura, Keith Slessor (Simon Fraser University) and Alison Mercer showed that a major component of queen pheromone, homovanillyl alcohol, alters the function of dopamine pathways in the brain. In young workers exposed to their mother's pheromone, levels of dopamine in the bee brain, as well as the levels of dopamine receptor gene expression, are reduced.

As a result, the brain's responses to this important modulator are changed dramatically. The pheromone's effects on brain function are profound. What are the consequences for the animal?

The 'bee team' has recently extended their study to explore the effects of queen pheromone on learning in bees. The results are surprising. In a paper appearing this week in Science, Vanina Vergoz, Haley Schreurs and Alison Mercer show that aversive olfactory learning in young worker bees is completely blocked by queen pheromone.

Young bees exposed to their mother's pheromone cannot learn to associate odours with a nasty or negative outcome. The effect is not permanent, nor is it a general learning deficit. Vergoz et al. show that queen pheromone's effects on aversive learning are age dependent, and that appetitive (i.e. food related) learning in young bees is not affected by the pheromone. Why block aversive learning in young workers?

Young worker bees perform many essential tasks. Arguably their most important role is to feed and groom the queen, and to distribute her pheromones throughout the colony. By blocking aversive learning in young workers, the queen may be making her own life and that of the colony more secure.

Exposure to their mother's pheromone will prevent young workers from developing an aversion to odours within the hive, including odours produced by the queen herself. With increasing age, however, worker bees start to leave the colony in search of food.

For these foraging bees, aversive learning is as an important survival tool and Vergoz et al. have found that by the time bees begin foraging, their ability to learn and recall information about noxious stimuli is no longer affected by the queen's pheromone bouquet.

One of the biggest challenges in understanding how brains work is working out how brain processes are linked to behaviour, says Professor Mercer.

"We have been able to link events at the cellular and molecular level with changes in the behaviour of the bee. Finding out how queen bees use chemicals to manipulate the behaviour of their offspring is creating a window into understanding the brain of this truly remarkable animal."

This work has been supported by a grant from the RSNZ Marsden Fund.