The Editors of The Journal of Experimental Biology are pleased to announce that Dr Audrey Dussutour from the University of Sydney is the winner of this year's JEB Outstanding Paper Prize. The award is announced on the 28th November in The Journal of Experimental Biology at http://jeb.biologists.org.
This annual prize recognises the contribution of an outstanding young scientist to an exceptional research paper. Dussutour was the first author on the paper 'Carbohydrate regulation in relation to colony growth in ants' (Dussutour and Simpson, 2008) and admits that she was 'very happy and surprised,' when she received the news. 'I had to read the email twice,' she admits. 'At first I wasn't sure if the journal wanted me to apply, but then I realised that I had won,' she laughs. Hans Hoppeler, Editor-in-Chief of The Journal of Experimental Biology says 'I like this paper because it took one of the dominant questions of biology: "how do animal's adjust their energy intake?" from the level of the collective'. Analysing ant foraging habits in response to differently structured colonies, Dussutour and Simpson found that the larvae's appetite for sugar seems to drive the nest's collective stomach.
Steve Simpson, Dussutour's mentor and co-investigator on the paper, says that this discovery is surprising from an ant foraging perspective, but not from a nutritional perspective. Simpson has a long-standing background in nutrition, having studied animals ranging from locusts to humans, but he had never studied the nutritional requirements of social animals. Dussutour comes from a strong ant behaviour background, having worked with Vincent Fourcassié in Toulouse and Jean-Louis Deneubourg in Brussels on ant traffic jams: or to be more correct the absence of ant traffic jams. 'They never happen, no matter how crowded you make the ants' says Dussutour. So, when Simpson became interested in the problem of how a few forager ants respond to the nutritional needs of the entire nest, it was natural that Dussutour joined Simpson's lab at the University of Sydney to find out how ant nests regulate their diet.
Dussutour explains that when an individual regulates its nutritional intake, all it has to do is listen to its own stomach. But it is a completely different matter for a colony where only 10% of the population supplies everyone's needs. The foragers must listen not only to their own needs but also the needs of the entire colony. So how does the colony regulate its nutritional intake and communicate its needs to the small number of foragers that keep it supplied?
Focusing on how ants regulate their sugar intake in good and bad times, Dussutour and Simpson offered individual ants concentrated and dilute sugar solutions to find out how they responded when they only had themselves to think of. 'Adult ants can survive without food' explains Dussutour, and having tested out the sugar solutions, the ants tucked into the concentrated sugar solution while ignoring the weaker solution: they would prefer to go without rather than eat a poor quality sugar solution.
But what happened when the foragers had to start thinking of their entire community? Starting out with 18 adult-only colonies, Dussutour offered them either a dilute, medium strength or concentrated sugar solution diet. Over the first few weeks, the colonies regulated their sugar intake to some extent, with the colony on the strongest sugar solution gorging until it was full, while the colony on the dilute sugar diet preferred to starve at first rather than consume the unpalatable 'nectar'.
However, things changed when larvae started coming along. All three colonies started regulating their sugar intake much more precisely, with the 'dilute sugar' colony sending out more foragers and doubling the amount of sugar they took home, even though they would have preferred to starve if left to their own devices.
Realising that the colony's behaviour had changed significantly when the ravenous larvae started arriving, Dussutour and Simpson manipulated the colonies' populations by adding either adults or larvae to see how the foragers responded. They found that increasing the numbers of adults didn't alter the foragers' behaviour at all. However, it was a different matter when they doubled the number of larvae. This time the colonies sent out legions of foragers to meet the colonies' demands.
But why do the foragers respond so strongly when there are young in the nest? Simpson explains that the foragers respond to the demands of the individuals that have the highest metabolic requirements, which are the fast-growing larvae. He explains that there must be a feedback mechanism from the larvae via the nurse ants that keep them supplied. If the sugar solution is dilute, the young need to consume more so the nurses somehow recruit more foragers to satisfy the youngsters' hunger. However, when the foragers hit on a rich supply, even the voracious larvae eventually fill up, leaving the nurses with more sugar solution than they need, taking the pressure off the hard-worked foragers. 'The colony is like a super mouth and gut' says Simpson.
So what next for Dussutour? Having come to the end of her postdoctoral fellowship in Simpson's lab, Dussutour is preparing to return to her first love, ant traffic management, back in Toulouse where she has been awarded a prestigious CNRS position. Simpson admits that he is 'very proud and very sad to lose her, but it has been a terrific couple of years,' and he is looking forward to continuing their collaboration when she has students and postdocs of her own.
Journal
Journal of Experimental Biology