Smaller ants devote more of their resting energy budget to their brains
The energy required for brains of different sizes to function could play a role in how different species evolved over time. While the energetic costs of brains have long been deemed important in evolution, direct measurements of the rate at which the brains of different species consume energy, also known as brain metabolic rates (MRs), remain scarce.
Researchers at Arizona State University and Boston University have found that smaller worker ants allocate a larger proportion of their resting energy budget to their brains compared to ants with larger workers. This energy allocation was observed in a study of 11 species of harvester ants, a type of ant found in North and South America.
The researchers tested three main hypotheses regarding brain metabolic rates (MRs) in these ants. While they found no link between colony size and brain MR, they did discover that smaller worker ants had relatively larger brains and higher brain MRs. Brain metabolism accounted for 38% of resting metabolism in species with the smallest workers, compared to just 6% in those with the largest workers.
The study suggests that smaller worker body sizes may require higher brain mass-specific energetic costs, potentially due to evolutionary pressures favoring neurometabolic frugality in larger-bodied species.
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