Collaborative Research: Brain Size, Metabolism, and Sociality in Ants

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The brain is an extraordinarily complex organ that generates behavior. Understanding brain size, structure, and function are among the most important frontiers of science. Brain size is considered to be influenced by social life, but the relationship is unclear. The research will address two significant questions: how does the brain change with body size, and how is brain function affected by the social nature of species. These questions will be addressed by comparing different species of ants, which are remarkably variable in size and social life. Ant brain sizes will be computed using a novel method and a new highly sensitive technique will allow energy use in individual brains to be measured. By comparing colonies that exhibit large size and division of labor with less socially complex small colonies, the effects of social life on brain size and energy use can be understood. Broad insights into the factors that affect brain evolution in all animals, including humans, will be gained. The project will train the next generation of scientists to become skilled in research, and will engage teachers and students to improve the experience of K-12 science education. The science curriculum of students from underrepresented groups and diverse minorities at the Laboratory Schools of the University of Chicago and Boston-, Phoenix-, and Providence-area schools will be enriched. The project will broadly address critical national needs to improve science literacy and inspire career choices that will enhance the global competitiveness of the United States.The hypothesis that complex social life selects for increased brain size and adaptive compartmental allometries to neurally support behavior is controversial and continues to be tested and debated. Importantly, the energetic cost of operating the brain is virtually unknown. Eusocial insects offer excellent models to address these questions of brain evolution. The PIs will robustly sample brain size, scaling, and metabolism in ant species that range widely in social complexity (colony size, physical caste) and worker body size to test the hypothesis that the energetics of ant brain tissue are independent of worker body size, morphological caste, or species, and thus scale in direct proportion to brain size. Scaling relationships of brain size and metabolism - and metabolic rates of brain regions that have social functions - with worker body size and colony size will be assessed. Respiration rates of individual worker brains and individual workers will be measured to determine the integrative physiological principles governing the evolution of brain size, structure, and function in the context of ant social evolution. Employing an integrated workflow connecting labs between research and primarily undergraduate institutions, brain templates from confocal images will be computationally constructed to automate and thus rapidly quantify brain size and structure. Scaling relationships of functionally differentiated brain regions and estimates of brain and body metabolic rates will be determined.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.