Audrey Dussutour wins outstanding journal paper prize

2 December 2008

Dr Audrey Dussutour, from the School of Biological Sciences, has won the 2008 Outstanding Paper Prize from the Journal of Experimental Biology. This prestigious international prize is awarded annually by the journal's editors to an outstanding young scientist for their contribution to an exceptional research paper published during the year.

Dr Audrey Dussutour's paper on nutritional regulation in green headed ants (Rhytidoponera metallica) has won the 2008 Outstanding Paper Prize from the Journal of Experimental Biology.
Dr Audrey Dussutour's paper on nutritional regulation in green headed ants (Rhytidoponera metallica) has won the 2008 Outstanding Paper Prize from the Journal of Experimental Biology.

Dr Dussutour won for her paper titled 'Carbohydrate regulation in relation to colony growth in ants', which was published in the journal earlier in 2008. She is the first author on the paper, with Professor Steve Simpson, also from the School of Biological Sciences, as the second author.

"I was very happy and surprised when I received the news. I had to read the email twice - at first I wasn't sure if the journal wanted me to apply for the award, but then I realised that I had won!" laughed Dr Dussutour.

Using common Australian green headed ants (Rhytidoponera metallica), Dr Dussutour's research investigated whether ants are able to regulate their food intake and under what conditions the colony's nutritional needs change.

"Ants, and in fact all social insects, are faced with an interesting nutritional challenge: rather than eating for one as most species do, a small number of foragers bring in the food for the whole colony," explained Dr Dussutour.

"We wanted to see how ants maintain their carbohydrate intake at both a collective and an individual level in response to changes in factors such as the concentration of sucrose made available to them, the demography of the colony and larval growth."

Dr Dussutour offered forager ants from separate adult-only colonies either strong (18%), medium (9%) or weak (4.5%) sucrose solution over a six week period and observed their feeding behaviours.

"At first, ants provided with the strong sugar solution consumed most and sent out the most foragers to collect food compared to the colonies provided with weaker sugar solutions. But over time, this pattern reversed, so that the number of ants that fed and the volume ingested by each ant was a negative function of the sugar concentration provided.

"Colonies regulated their sugar intake over time but were not particularly good at it at first. I wanted to see whether having larvae in the nest would make them more careful with their diets - whether having young in the colony would make them better at regulating their intake."

Either larvae or adults were added to each experimental colony from their original nest to increase the colony size, and the volume of sucrose taken and the numbers of foragers sent out were monitored.

"When colonies were made larger by adding more adult ants, the colonies only sent out enough foragers to cover the extra mouths. However, the colonies that had larvae added not only sent out more foragers, but also massively increased the volume of dilute sucrose carried back to the nest," said Dr Dussutour.

"More larvae in the nest made the colony regulate their consumption of sugar more accurately, compared to having more adults in the colony, suggesting that larvae play an important role in providing nutritional feedback to workers."

The research also showed that ants defend a carbohydrate 'intake target' by allowing them to select among sugar solutions of different concentrations.

To test whether these findings are different for individual ants or those in colonies, Dr Dussutour isolated individual ants from their colonies - some isolated totally for the experimental period and others isolated just for one hour per day - and offered them concentrated and dilute sugar solutions.

"The totally isolated ants ingested the greatest volume of diluted solution and the least amount of concentrated solution. Adult ants can survive without food, so when they didn't have to consider the needs of their colony or demanding larvae, individual ants would prefer to go without rather than eat a poor quality sugar solution," explained Dr Dussutour.

Professor Steve Simpson, who worked with Dr Dussutour on this research, has a long-standing background in nutrition, having studied animals ranging from locusts to humans.

"These discoveries are surprising from an ant foraging perspective, but not from a nutritional perspective," said Professor Simpson.

"In the colony, the forager ants respond to the demands of the individuals that have the highest metabolic requirements - the fast-growing larvae. There must be a feedback mechanism from the larvae to the adult ants, probably through the nurse ants that keep the larvae supplied. The colony is like a super mouth and gut," explained Professor Simpson.

Hans Hoppeler, Editor in Chief of the Journal of Experimental Biology said, "I like this paper because it took one of the dominant questions in biology: 'how do animals adjust their energy intake?' from the level of the collective."

Contact: Katynna Gill

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