TY - JOUR
T1 - Muscle fibre types in the reduced forelimb and enlarged hindlimb of the quokka (Setonix brachyurus, Macropodidae)
AU - Casinos, A.
AU - Milne, Nick
AU - Jouffroy, F.K.
AU - Médina, M.F.
PY - 2016
Y1 - 2016
N2 - © 2016 CSIRO.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 quokka's 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).
AB - © 2016 CSIRO.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 quokka's 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).
U2 - 10.1071/ZO15055
DO - 10.1071/ZO15055
M3 - Article
SN - 0004-959X
VL - 64
SP - 277
EP - 284
JO - Australian Journal of Zoology
JF - Australian Journal of Zoology
IS - 4
ER -