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Muscle fibre types in the reduced forelimb and enlarged hindlimb of the quokka (Setonix brachyurus, Macropodidae)

Muscle fibre types in the reduced forelimb and enlarged hindlimb of the quokka (Setonix... The quokka (Setonyx brachyurus) is restricted to two offshore islands and small isolates on the mainland of south-western Australia. It displays a tendency to saltatorial locomotion and moves at speed by bipedal hopping, although it also uses its forelimbs at low speed. Its bipedal adaptation involves enlarged hind limbs, with elongated feet. The fibre type distribution of the elbow and knee extensors, and the ankle plantar flexors, in comparison with two eutherians, the quadrupedal rhesus monkey, as a locomotor generalist, and the jerboa, a small eutherian hopping species morphologically similar to the quokka, were studied. The quokkas forelimb showed the same characteristics as that of the jerboa, lacking the fatigue-resistant Type I fibres that are used to sustain posture. As in the jerboa, the gastrocnemius lateralis was the muscle head with the highest proportion of fast twitch fibres. Muscular fibre pattern is not identical in the quokka and the jerboa hindlimb, but it appears that both species have similar anatomical adaptations to saltatorial locomotion. Differences in muscle fibre proportions could be due to several factors including, resting posture, body size and the propensity for elastic energy storage, the burrowing behaviour of the jerboa, but also to phylogenetic constraints where the adaptation to hop on the hindlimbs is a shared behaviour of the Macropodoidea (jerboas are the only Dipodidae to have elongated hindlimbs). http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Australian Journal of Zoology CSIRO Publishing

Muscle fibre types in the reduced forelimb and enlarged hindlimb of the quokka (Setonix brachyurus, Macropodidae)

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References (48)

Publisher
CSIRO Publishing
Copyright
Copyright © The Author(s). Published by CSIRO Publishing
ISSN
0004-959X
eISSN
1446-5698
DOI
10.1071/ZO15055
Publisher site
See Article on Publisher Site

Abstract

The quokka (Setonyx brachyurus) is restricted to two offshore islands and small isolates on the mainland of south-western Australia. It displays a tendency to saltatorial locomotion and moves at speed by bipedal hopping, although it also uses its forelimbs at low speed. Its bipedal adaptation involves enlarged hind limbs, with elongated feet. The fibre type distribution of the elbow and knee extensors, and the ankle plantar flexors, in comparison with two eutherians, the quadrupedal rhesus monkey, as a locomotor generalist, and the jerboa, a small eutherian hopping species morphologically similar to the quokka, were studied. The quokkas forelimb showed the same characteristics as that of the jerboa, lacking the fatigue-resistant Type I fibres that are used to sustain posture. As in the jerboa, the gastrocnemius lateralis was the muscle head with the highest proportion of fast twitch fibres. Muscular fibre pattern is not identical in the quokka and the jerboa hindlimb, but it appears that both species have similar anatomical adaptations to saltatorial locomotion. Differences in muscle fibre proportions could be due to several factors including, resting posture, body size and the propensity for elastic energy storage, the burrowing behaviour of the jerboa, but also to phylogenetic constraints where the adaptation to hop on the hindlimbs is a shared behaviour of the Macropodoidea (jerboas are the only Dipodidae to have elongated hindlimbs).

Journal

Australian Journal of Zoology – CSIRO Publishing

Published: Dec 1, 2016

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