Personality, immunity and the bumblebee
Good news for particularly busy bumblebees: you're not putting your immune systems at risk with all that hard work. EU-funded research has established that foraging motivation and other traits vary among individuals and colonies of the species, but that these differences dont seem to affect their ability to fend off disease.
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Bumblebees do indeed have different personalities, it appears, and company culture also varies from one colony to another. The EU-funded project ColonyPersPOLs focused on the fuzzy foragers idiosyncrasies and the implications of these traits. It concluded that temperament has no bearing on the insects individual or collective immune capacity.
These findings do not support a widely held assumption that insects living life in the fast lane invest less energy in building up their immune systems than less driven peers, reports David Baracchi, who led the research at the Queen Mary University of London.
Bolder animals are thought to have a shorter life expectancy, Baracchi says. They may have less time to reach milestones on their lifes journey reproduction, for example than other members of their species. The go-getters were therefore thought to invest more energy in meeting their evolutionary objectives, diverting it away from housekeeping activities such as building up a strong immune system, he adds.
This hypothetical reallocation of resources is referred to as pace-of-life syndrome. It is basically a trade-off between speed and the probability of completing what they have to do, Baracchi explains. So, is this actually what happens? Apparently not, according to ColonyPersPOLs research. We did not find in our experiment that investment in immunity correlates with behavioural type, as Baracchi puts it.
But first, the project had to prove that members of the species arent actually all alike in terms of their foraging motivation, boldness, and willingness to explore new things. Testing for these parameters involved an artificial environment with plastic flowers, Baracchi explained.
The introduction of new types of flowers enabled the team to measure individual bumblebees interest in novelty, and their diligence in visiting familiar flowers provided clues to their motivation. But how do you test a bee for boldness?
By observing how quickly it returns to business as usual after a simulated predation attack, for example.
We used a kind of mechanical spider that briefly trapped bees in one of the flowers, Baracchi explains. And then we counted the time it took them to resume their foraging activity. Some only needed a few seconds, others a couple of minutes.
The colonies many bumblebee species form also differ in their habits, says Baracchi. Some produce few males and queens and do so very early in the season, for example, he notes. Other colonies, in contrast, may focus on the production of workers initially and only generate reproductive bees towards the end of the season. However, they are likely to produce a lot of them, and these males and queens will probably also be of better quality as there are more workers to feed them.
The researchers completed their experiment by taking note of the size and body mass of the tested bees, counting the number of immune cells in their blood, and attempting to correlate these characteristics with the observed traits.
No such correlation emerged, Baracchi reports. Individuals and colonies have the same tasks to complete throughout their lives or cycles, and some may tackle these tasks faster than others but no trade-offs in terms of the energy invested in reproduction, physiology or immune capacity appear to be involved, he adds.
ColonyPersPOLs benefited from EU funding, in the form of a career integration grant awarded to Baracchi by the Marie Skłodowska-Curie Actions programme. Following the end of this two-year project in February 2015, he was offered a position in Toulouse, where his research on insects now focuses on mechanisms of learning and memory.
A three-year project dedicated to these aspects of insect cognition will take him back to his native Italy in 2018, Baracchi adds. Methodology developed in ColonyPersPOLs will feed into this research, he notes.