Functional anatomy of the gibbon forelimb: adaptations to a brachiating lifestyle

Authors

  • Fana Michilsens,

    1. Laboratory for Functional Morphology, University of Antwerp, Belgium
    2. Centre for Research and Conservation, Royal Zoological Society of Antwerp, Belgium
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  • Evie E. Vereecke,

    1. Laboratory for Functional Morphology, University of Antwerp, Belgium
    2. Department of Human Anatomy and Cell Biology, School of Biomedical Sciences, University of Liverpool, UK
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  • Kristiaan D'Août,

    1. Laboratory for Functional Morphology, University of Antwerp, Belgium
    2. Centre for Research and Conservation, Royal Zoological Society of Antwerp, Belgium
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  • Peter Aerts

    1. Laboratory for Functional Morphology, University of Antwerp, Belgium
    2. Department of Movement and Sport Sciences, University of Ghent, Belgium
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Fana Michilsens, Laboratory for Functional Morphology, University of Antwerp, CDE – Universiteitsplein 1 – 2610 Wilrijk, Belgium. E: fana.michilsens@ua.ac.be

Abstract

It has been shown that gibbons are able to brachiate with very low mechanical costs. The conversion of muscle activity into smooth, purposeful movement of the limb depends on the morphometry of muscles and their mechanical action on the skeleton. Despite the gibbon's reputation for excellence in brachiation, little information is available regarding either its gross musculoskeletal anatomy or its more detailed muscle–tendon architecture. We provide quantitative anatomical data on the muscle–tendon architecture (muscle mass, physiological cross-sectional area, fascicle length and tendon length) of the forelimb of four gibbon species, collected by detailed dissections of unfixed cadavers. Data are compared between different gibbon species and with similar published data of non-brachiating primates such as macaques, chimpanzees and humans. No quantitative differences are found between the studied gibbon species. Both their forelimb anatomy and muscle dimensions are comparable when normalized to the same body mass. Gibbons have shoulder flexors, extensors, rotator muscles and elbow flexors with a high power or work-generating capacity and their wrist flexors have a high force-generating capacity. Compared with other primates, the elbow flexors of gibbons are particularly powerful, suggesting that these muscles are particularly important for a brachiating lifestyle. Based on this anatomical study, the shoulder flexors, extensors, rotator muscles, elbow flexors and wrist flexors are expected to contribute the most to brachiation.

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