French researchers have discovered a direct link between nutrition and lifespan in ants. Their research suggests that a high protein intake severely decreases lifespan in worker ants and may be a leading cause in Colony Collapse Disorder. Their findings may serve to fuel the discussion on just what is causing the massive number of deaths of honeybees.
Audrey Dussutour and Steve Simpson from the University of Toulouse, France, followed the life of more than 120 colonies of the black garden ant, Lasius niger. Their goal was to find out if there was a link between what the ants eat and how much they live. More specifically, they looked at how a high-protein diet affected the longevity of individual worker ants. Their work is published today in the Proceedings of the Royal Society B.
As Audrey Dussutour explains, "We achieved our initial aim of understanding how diet quality affects longevity at both the individual and collective level (an important issue for the study of aging and social organization). We showed that protein over-feeding decreased lifespan by up to ten fold."
Their results also suggest that exposure to a high protein diet had detrimental effects that were hard to get rid off, as Audrey Dussutour tells The Munich Times:
"Remarkably, colonies paid the longevity cost of a high-protein diet after only one day of exposure, reducing population size by over 20%, even if they were subsequently shifted to an optimal, high-carbohydrate diet."
Why should bees care about this?
Just like ants, honeybees are social insects, and they too may be affected by what they eat. Since Autumn 2006, a dramatic fall in the population of honeybees has been occurring in the United States, causing around 30%-40% reduction in bee colony size each year. The disease, officially known as Colony Collapse Disorder (CCD), is for the most part a mystery.
Now, with this new research, Audrey Dussutour and Steve Simpson think they may add some new insights into the discussion of what is killing the honeybees:
"Interestingly, our results have important implications for understanding CCD in honey bees. Bee colonies are now increasingly commonly provisioned with a commercially available protein supplement, aimed to increase the production of brood. Such 'pollen substitutes' are high-protein mixtures (typically around 40% protein, as compared to 25% in pollen) that are used to replace or augment pollen in the diet. We are left wondering whether CCD is a consequence of protein over-feeding."
But not everyone agrees.
Christian Pirk is a professor at the Department of Zoology and Entomology, University of Pretoria, South Africa, and his research on honeybees tackles various topics, including how diet affects their lifespan.
"I think the work is really nicely done and the authors present nice and convincing data for ants... but I think it 'stretches' a little bit far by making conclusions about honeybees.
That lifespan is affected by proteins is not new... I think protein-rich diet could play a role for a small number of the colony losses but is definitely not the main cause".
In reply, Audrey Dussutour had this to say:
"We are just saying that substitutes need to include ingredients that balance honey bee nutritional requirements to avoid high levels of toxic substances like crude protein. We suggest that at the heart of many colony deaths is poor nutrition that acerbates the stress bees experience from parasitic mites, disease and environmental toxins. We are of course aware that there are other factors playing a role in CCD, we are just stressing the fact that nutrition might have been overlooked."
All in all, this work serves to heat up the discussion on just how important diet is in the life of social insects, in particular that of honeybees in which we so much rely on, yet still have a lot to learn about. Their finding that even short exposure time to a detrimental diet has a long lasting effect, is a new piece of information that will likely instigate new research on honeybees and other social insects.
As far as honeybees go, the link between CCD and diet needs more work; in particular "There is a need to quantify the relationship", as Steve Simpson suggested. Also, honeybees are commonly fed artificial diets, and we need to know exactly what is being included in these diets and who is using them, as Audrey Dussutour tells us:
"We don't have any idea of the extent of pollen substitute usage as many beekeepers make their own supplement (you can find lots of different recipes on the Internet), and they are encouraged to do so to prevent CDD "
Christian Pirk and other bee experts are left with the task of understanding what exactly is the perfect diet for honeybees and whether this is an important aspect of their health.