Journal article
How to build your dragon: scaling of muscle architecture from the world's smallest to the world's largest monitor lizard
Frontiers in Zoology, Vol.13, 8
2016
Abstract
Background: The functional design of skeletal muscles is shaped by conflicting selective pressures between support and propulsion, which becomes even more important as animals get larger. If larger animals were geometrically scaled up versions of smaller animals, increases in body size would cause an increase in musculoskeletal stress, a result of the greater scaling of mass in comparison to area. In large animals these stresses would come dangerously close to points of failure. By examining the architecture of 22 hindlimb muscles in 27 individuals from 9 species of varanid lizards ranging from the tiny 7.6 g Varanus brevicauda to the giant 40 kg Varanus komodoensis, we present a comprehensive dataset on the scaling of musculoskeletal architecture in monitor lizards (varanids), providing information about the phylogenetic constraints and adaptations of locomotor muscles in sprawling tetrapods. Results: Scaling results for muscle mass, pennation and physiological cross-sectional area (PCSA), all suggest that larger varanids increase the relative force-generating capacity of femur adductors, knee flexors and ankle plantarflexors, with scaling exponents greater than geometric similarity predicts. Thus varanids mitigate the size-related increases in stress by increasing muscle mass and PCSA rather than adopting a more upright posture with size as is shown in other animals. As well as the scaling effects of muscle properties with body mass, the variation in muscle architecture with changes in hindlimb posture were also prominent. Within varanids, posture varies with habitat preference. Climbing lizards display a sprawling posture while terrestrial lizards display a more upright posture. Sprawling species required larger PCSAs and muscle masses in femur retractors, knee flexors, and ankle plantarflexors in order to support the body. Conclusions: Both size and posture-related muscle changes all suggest an increased role in support over propulsion, leading to a decrease in locomotor performance which has previously been shown with increases in size. These estimates suggest the giant Pleistocene varanid lizard (Varanus megalania priscus) would likely not have been able to outrun early humans with which it co-habitated the Australian landmass with.
Details
- Title
- How to build your dragon: scaling of muscle architecture from the world's smallest to the world's largest monitor lizard
- Authors
- Taylor J M Dick (Author) - Simon Fraser University, CanadaChristofer J Clemente (Author) - University of the Sunshine Coast - Faculty of Science, Health, Education and Engineering
- Publication details
- Frontiers in Zoology, Vol.13, 8; 17
- Publisher
- BioMed Central Ltd.
- Date published
- 2016
- DOI
- 10.1186/s12983-016-0141-5
- ISSN
- 1742-9994; 1742-9994
- Copyright note
- Copyright © 2016 Dick and Clemente. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
- Organisation Unit
- School of Science and Engineering - Legacy; University of the Sunshine Coast, Queensland; School of Science, Technology and Engineering
- Language
- English
- Record Identifier
- 99449112602621
- Output Type
- Journal article
- Research Statement
- false
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