Controlling the Kids with Chemicals
30 Jul, 2007 10:20 am
Honey bee queens control their offspring with chemicals (pheromones), but how these chemicals work has largely remained a mystery. Alison Mercer and her research team at the University of Otago, New Zealand have discovered that exposing young worker bees to queen pheromone alters the chemistry of the honey bee brain. Their study provides a direct link between changes in brain biochemistry and complex behaviour.
In a paper appearing this week in Science, Vanina Vergoz, Haley Schreurs and Alison Mercer show that young bees exposed to queen pheromone cannot learn to associate odours with a nasty or negative outcome. This is known as aversive learning, and in young worker bees exposed to their mother’s pheromone this form of learning is completely blocked. The effect is not permanent, nor is it a general learning deficit. The pheromone’s effects on aversive learning are age dependent, and Vergoz et al. show that appetitive (i.e. food related) learning in young bees is not affected at all.
Why block aversive learning in young workers: what advantage might this be to the queen and her colony? Young worker bees perform many essential duties within the colony including cleaning the hive and caring for developing brood. Arguably their most important task, however, 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 in the colony, including odours produced by the queen herself. This would ensure that young bees remain in attendance of the queen, thus enhancing her reproductive success, as well as her chances of survival.
With increasing age, however, worker bees start to leave the colony in search of food. For these foraging bees, aversive learning is an important survival tool. Vergoz et al show 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. Forager bees can thus learn to avoid dangers they encounter outside the confines of the hive.
For anyone interested in how brains work, one of the biggest challenges lies in revealing how processes observed in the brain relate to behaviour. The work of Mercer and her colleagues links directly 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.
Acknowledgement: This work was supported by a grant from the Royal Society of New Zealand Marsden Fund (UOO312).
Vergoz V., et al, Queen Pheromone Blocks Aversive Learning in Young Worker Bees, Science 20 July 2007: Vol. 317. no. 5836, pp. 384 - 386