Macronutrient regulation by the desert leafcutter ant Acromyrmex versicolor
Nathan Smith, Nathan Smith , Jennifer Fewell
School of Life Sciences, Arizona State University, Tempe, Arizona; School of Life Sciences, Arizona State University, Tempe, Arizona, USA ; School of Life Sciences, Arizona State University, Tempe, Arizona, USA
Leafcutter ants live in an obligate mutualism with a fungal food source. The leaf fragments which the ants harvest are provided to their fungal symbiont, which the ants in turn consume. As a result, leafcutter ants must make foraging decisions based not directly on their own nutritional needs, but on those of the ant/fungus colony system. A large body of nutritional research suggests that animals forage to obtain nutrients in specific relative amounts based on physiological needs. This investigation focused on how colonies of the desert leafcutter ant Acromyrmex versicolor balance collection of two important macronutrients: protein and carbohydrates. The results indicate that A. versicolor colonies forage to a specific target ratio of protein:carbohydrates. This ratio is carbohydrate-biased, with foragers collecting approximately 1 gram of protein for every 7 grams of carbohydrates. The ants also store food inside their nests, and I will discuss potential differences between the ratio of macronutrients that are collected by foragers, stored in the nest, or provisioned to the fungus. I will also discuss how the ability of colonies to regulate nutrient intake may emerge from variation in individual foraging choices.