Metabolic Scaling of Ants

i-45b6ec98082af03cfd5178702e4a6519-ant-thumb-250x193-57818.png The research of James Waters and Jon Harrison from Arizona State University on ant metabolism was recently featured in a press release from The American Physiological Society.

Mr. Waters and Dr. Harrison have measured the standard metabolic rates of individual ants as well as whole ant colonies. What they found was that the colony produced only 75% of the by-products that would be produced by individual ants if each lived in isolation. In other words, the metabolism of the colony was less than the sum of each individual ant’s metabolism. Moreover, they found that larger colonies had lower metabolic rates than smaller colonies. It is so fascinating that the metabolism of an ant colony scales at 0.75 since this scaling exponent holds for many organisms and appears to be conserved in nature.

In the press release, Mr. Waters describes how these findings in ants might be relevant to human health. According to Waters, because ant colonies behave metabolically like individual organisms, studying how a colony’s size changes its metabolism could offer useful insight for developing theories about medication dosage in humans. “It’s hard to figure out how size affects metabolic rate in individuals because it’s not easy to change an individual’s size,” he said. “With an ant colony, it’s as easy as adding or removing individual ants.”

This is not to say that ant colonies function like individual humans. Rather, ant colonies could serve as a model for testing theories about the role of networks among cells in human metabolism. He continues: “We’ve got this pattern where the larger an organism is, the slower its metabolism, and we don’t really understand why,” said Mr. Waters. “It’s important to find out because we really don’t have any sort of theoretical basis for deciding the right dose of medication. We can do charts on weight, and we can run tests on animals, but it’s really more alchemy than science.”

Waters’ research interests focus on evolutionary and comparative physiology, social insect colony energetics, allometric scaling of metabolic rate, interaction network motifs, imaging methods, modeling gas exchange, and insect biomechanics. I think the publications and abstracts are interesting.

Comments

  1. #1 Sven DIMilo
    November 11, 2010

    the colony produced only 75% of the by-products that would be produced by individual ants if each lived in isolation…It is so fascinating that the metabolism of an ant colony scales at 0.75 since this scaling exponent holds for many organisms

    The OP and the press release seem to imply imply that these statements mean the same thing. They don’t.

    “We’ve got this pattern where the larger an organism is, the slower its metabolism, and we don’t really understand why,”

    Man, I hate this.
    Of course, the larger an organism is, the “faster” its metabolic rate (J/h, e.g.). That–whole-animal metabolic rate–is what scales at 0.75.

    from the press release:

    “As creatures go from small to large, their mass-specific metabolic rate decreases. It’s a broad pattern in biology,” he said. “When you graph these patterns, you can see how metabolism decreases as a creature gets bigger, and the exponent is usually near 0.75.”

    Yes, mass-specific metabolic rate decreases with increasing size, but that means that mass-specific metabolic rate scales at -0.25.

    Cool study, though.

  2. #2 James Waters
    November 12, 2010

    Sven, you raise all great points! I encourage you to check out our paper in The American Naturalist and let me know if there are any phrasings in the paper that you are not satisfied with. I usually speak about our research using terminology from mathematics and allometry, but these are rarely choice terms to use in a press release for the general public. We could have been a bit more accurate with respect to using the word relative to indicate that smaller colonies don’t exhibit strictly faster metabolic rates, but rather, relatively faster rates, with respect to colony size, i.e. higher mass-specific metabolic rates. Thanks for appreciating our work!

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