Meeting Abstract
Ants are extremely ecologically successful due in large part to an efficient division of labor among workers based on age and size. While differences in learning ability and responsiveness to environmental stimuli likely generate variation in worker behavior, few studies have addressed how variation in learning and memory ability among workers might impact colony division of labor, or how variation in neurophysiological mechanisms known to regulate division of labor could affect learning ability. The biogenic amine neuromodulators, including dopamine, serotonin, and octopamine, are particularly interesting in this context because they are widely implicated in learning across vertebrates and invertebrates and they have independently been linked to division of labor in multiple social insect species. Using workers of the carpenter ant species Camponotus americanus, in which division of labor is heavily influenced by body size, we performed behavioral observations to assess worker foraging behavior, experimentally measured learning ability in workers of different sizes, and used HPLC to determine neuromodulator levels in the brains of these workers. While larger workers were overrepresented outside the nest, they were found much closer to the nest entrance than smaller workers, which appear to be more active foragers. Smaller workers had better learning abilities and, after correcting for brain size differences, significantly higher brain amine levels than larger workers. Together, these findings suggest that variation in learning ability may help generate size-related division of labor in C. americanus. Future work will involve experimental manipulations of brain neuromodulator levels to directly test whether higher aminergic activity improves learning performance.
