Social complexity influences brain investment and neural operation costs in ants

Kamhi, J. Frances, Gronenberg, Wulfila, Robson, Simon K.A., and Traniello, James F.A. (2016) Social complexity influences brain investment and neural operation costs in ants. Proceedings of the Royal Society of London Series B, Biological Sciences, 283 (1841). pp. 1-9.

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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.

Item ID: 46538
Item Type: Article (Research - C1)
ISSN: 1471-2954
Keywords: metabolic cost; social brain evolution; polymorphism; collective intelligence; cytochrome oxidase
Funders: National Science Foundation (NSF), Australian Research Council (ARC)
Projects and Grants: NSF East Asia and Pacific Summer Institute grant 1209967, NSF IOB-0725013, NSF IOS-1354291, ARC Discovery grant 1093553
Research Data:
Date Deposited: 01 Dec 2016 23:00
FoR Codes: 31 BIOLOGICAL SCIENCES > 3101 Biochemistry and cell biology > 310104 Cell neurochemistry @ 40%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310301 Behavioural ecology @ 40%
31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310404 Evolution of developmental systems @ 20%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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