Social complexity influences brain investment and neural operation costs in ants

J. Frances Kamhi, Wulfila Gronenberg, Simon K.A. Robson, James F.A. Traniello

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


The 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.

Original languageEnglish (US)
Article number20161949
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1841
StatePublished - Oct 26 2016


  • Collective intelligence
  • Cytochrome oxidase
  • Metabolic cost
  • Polymorphism
  • Social brain evolution

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Immunology and Microbiology
  • General Environmental Science
  • General Agricultural and Biological Sciences


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