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First published online October 7, 2008
Journal of Experimental Biology 211, 3214-3225 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.020677

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The influence of oxygen and high-energy phosphate diffusion on metabolic scaling in three species of tail-flipping crustaceans

Ana Gabriela Jimenez^1,*, Bruce R. Locke² and Stephen T. Kinsey¹

¹ Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403-5915, USA
² Department of Chemical and Biomedical Engineering, Florida State University, FAMU-FSU College of Engineering, Tallahassee, FL 32310-6046, USA

^* Author for correspondence (e-mail: agj6818{at}uncw.edu)

Accepted 21 July 2008

We examined the influence of intracellular diffusion of O₂ and high-energy phosphate (HEP) molecules on the scaling with body mass of the post-exercise whole-animal rate of O₂ consumption (_O2) and muscle arginine phosphate (AP) resynthesis rate, as well as muscle citrate synthase (CS) activity, in three groups of tail-flipping crustaceans. Two size classes in each of three taxa (Palaemonetes pugio, Penaeus spp. and Panulirus argus) were examined that together encompassed a 27,000-fold range in mean body mass. In all species, muscle fiber size increased with body mass and ranged in diameter from 70±1.5 to 210±8.8 µm. Thus, intracellular diffusive path lengths for O₂ and HEP molecules were greater in larger animals. The body mass scaling exponent, b, for post-tail flipping _O2 (b=–0.21) was not similar to that for the initial rate of AP resynthesis (b=–0.12), which in turn was different from that of CS activity (b=0.09). We developed a mathematical reaction–diffusion model that allowed an examination of the influence of O₂ and HEP diffusion on the observed rate of aerobic flux in muscle. These analyses revealed that diffusion limitation was minimal under most conditions, suggesting that diffusion might act on the evolution of fiber design but usually does not directly limit aerobic flux. However, both within and between species, fibers were more diffusion limited as they grew larger, particularly when hemolymph P_O2 was low, which might explain some of the divergence in the scaling exponents of muscle aerobic capacity and muscle aerobic flux.

Key words: oxygen consumption, arginine phosphate, citrate synthase activity, aerobic metabolism, anaerobic metabolism, metabolic scaling, diffusion

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