Social complexity influences brain investment and neural operation costs in ants
AffiliationUniv Arizona, Dept Neurosci
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CitationSocial complexity influences brain investment and neural operation costs in ants 2016, 283 (1841):20161949 Proceedings of the Royal Society B: Biological Sciences
Rights© 2016 The Author(s) Published by the Royal Society. All rights reserved.
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AbstractThe metabolic expense of producing and operating neural tissue required for adaptive behaviour is considered a significant selective force in brain evolution. In primates, brain size correlates positively with group size, presumably owing to the greater cognitive demands of complex social relationships in large societies. Social complexity in eusocial insects is also associated with large groups, as well as collective intelligence and division of labour among sterile workers. However, superorganism phenotypes may lower cognitive demands on behaviourally specialized workers resulting in selection for decreased brain size and/or energetic costs of brain metabolism. To test this hypothesis, we compared brain investment patterns and cytochrome oxidase (COX) activity, a proxy for ATP usage, in two ant species contrasting in social organization. Socially complex Oecophylla smaragdina workers had larger brain size and relative investment in the mushroom bodies (MBs)-higher order sensory processing compartments-than the more socially basic Formica subsericea workers. Oecophylla smaragdina workers, however, had reduced COX activity in the MBs. Our results suggest that as in primates, ant group size is associated with large brain size. The elevated costs of investment in metabolically expensive brain tissue in the socially complex O. smaragdina, however, appear to be offset by decreased energetic costs.
NotePublished 19 October 2016; 12 month embargo.
VersionFinal accepted manuscript
SponsorsNational Science Foundation (NSF) East Asia and Pacific Summer Institute ; NSF [IOB-0725013, IOS-1354291]; Australian Research Council