If you've ever moved to an unfamiliar neighbourhood and had to orientate yourself, you'll agree that worker honey bees are being brave when they exit their hives for the very first time. After weeks of tending her queen's latest offspring, a young worker will fearlessly spread her wings and undertake her first orientation flight before she begins her new role as a forager. ‘It's really a remarkable thing to watch this tiny insect leaving the colony’, says Claudia Lutz from University of Illinois Urbana-Champaign, USA. ‘She's going out into this environment that she's never been in before, she goes out of sight and is gone for several minutes before she comes flying back. The only purpose of this behaviour that we know of is for that bee to learn about her surrounding environment – she's not getting rewarded [for it], it's just
As learning requires a quick response to cement the lesson, Lutz realised that genes involved in orientating would have to be expressed quickly. She decided to screen the expression of 10 immediate early genes (so called because they have the ability to respond rapidly to stimuli) in young worker bees orientating for the first time. Her hunch paid off and she found that after just 30 min one of these genes, Egr, was specifically activated and upregulated in the brain's mushroom bodies (a region involved in learning).
So what was it about the orientating flight that caused this sudden and large increase in Egr expression? To rule out the possibility that it was simply exercise that increased Egr levels, Lutz turned to another of the bee's unique behaviours – acting as a primitive air conditioning unit when the hive heats up. Lutz explains: ‘They'll stand near the entrance and fan their wings to provide ventilation to the hive. It's a very vigorous wing beat that they're performing and they'll maintain it for a while, so it's really comparable to the type of exercise and motions that they're performing during flight.’ Lutz heated hives with a heat lamp and induced this behaviour, and confirmed that Egr expression didn't go up in these exercising bees.
Lutz wondered whether increased Egr levels were associated with worker bees learning how to fly for the first time. To test this, Lutz took bees that had already performed their pioneering flight and placed them in a new environment to re-orientate: ‘The only novel aspect in that situation is the environment itself and them exploring it, but we did find Egr upregulation in those bees, suggesting that it was something about the novel spatial environment and not something about a novel motor task’, says Lutz.
If Egr levels are increasing in response to novel environments, how exactly are the bees detecting their new surroundings? ‘An important part of the orientation flight is that they're learning landmarks in the nearby environment, so I thought what we might be seeing is a molecular signature basically of them learning those landmarks’, recalls Lutz. However, when young naive bees were freed to orientate in a room devoid of specific landmarks, Egr levels still increased, and even when bees were tethered in a white box and allowed to fly they still detected they were in a novel setting. Perhaps the bees can see something we can't or are better at sensing novelty than us but either way Egr is involved in novelty sensing.
