Clever bees show immune advantage
10 November 2008
Fast-learning bees are also better at fighting off infection, according to new research.
A radio-tagged bumblebee forages for nectar on a gorse flower.
Bees naturally prefer blue flowers to yellow. Using a specially-designed 'artificial meadow', scientists tested 180 bumblebees from 12 colonies for their ability to learn that yellow flowers offered more nectar than blue ones.
The more the bees learned to favour the former and ignore the latter over 99 attempts, the higher they scored. This meant the bees in the test had to learn to overcome their ingrained tendencies.
The researchers then took bees from the same colonies - hence with the same learning abilities - and tested their immune response to bacterial infection. The results were a surprise.
Both learning abilities and immune systems are costly items from an evolutionary perspective; developing them takes up lots of resources that are then not available for other potentially beneficial features.
The scientists had therefore hypothesised that bees with more ability to learn would be less able to resist disease, since putting more energy and resources into developing brainpower should leave bees with less room to invest in a robust immune system.
In fact, bees that learned more quickly turned out also to have stronger immune responses to infection. 'Bees from fast learning colonies are not only the best nectar collectors, but also better able to fight infections,' said Dr Nigel Raine of Queen Mary, University of London (QMUL), one of the paper's authors.
'These colonies are probably much better equipped to thrive under difficult conditions,' he added.
Resistance to infection is important to a social species like bees, since they come into close contract with so many other genetically-similar individuals in the nest.
The research was done by Raine at QMUL and Akram Alghamdi, Dr Ezio Rosato and Dr Eamonn Mallon from the University of Leicester.
Earlier research by the same team had already showed that bees get worse at learning when they are ill. It's possible that having to turn on their immune system to deal with infection takes away resources that could otherwise go towards brainpower, but that simply possessing a potentially-strong immune system does not.
'Good colonies are good colonies,' said lead author Mallon. 'There's a difference in cost between having a good immune system and activating the immune system.'
Another possible explanation for the apparent lack of a trade-off between learning and immune system capability is that scientists don't yet fully understand bees' immune systems, and that measuring a bee's response to microbes does not give a complete picture of its immune system's abilities.
The research appeared in the Royal Society journal Biology Letters.
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