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First published online October 30, 2009
Journal of Experimental Biology 212, 3664-3672 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.033688

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Skeletal muscle atrophy occurs slowly and selectively during prolonged aestivation in Cyclorana alboguttata (Günther 1867)

Beth L. Mantle¹, Nicholas J. Hudson², Gregory S. Harper², Rebecca L. Cramp¹ and Craig E. Franklin^1,*

¹ School of Integrative Biology, University of Queensland, St Lucia, Australia, 4072
² CSIRO Livestock Industries, St Lucia Bioscience Precinct, St Lucia, Australia, 4072

^* Author for correspondence (c.franklin{at}uq.edu.au)

Accepted 19 August 2009

We investigated the effect of prolonged immobilisation of six and nine months duration on the morphology and antioxidant biochemistry of skeletal muscles in the amphibian aestivator Cyclorana alboguttata. We hypothesised that, in the event of atrophy occurring during aestivation, larger jumping muscles were more likely to be preserved over smaller non-jumping muscles. Whole muscle mass (g), muscle cross-sectional area (CSA) (µm²), water content (%) and myofibre number (per mm²) remained unchanged in the cruralis muscle after six to nine months of aestivation; however, myofibre area (µm²) was significantly reduced. Whole muscle mass, water content, myofibre number and myofibre CSA remained unchanged in the gastrocnemius muscle after six to nine months of aestivation. However, iliofibularis dry muscle mass, whole muscle CSA and myofibre CSA was significantly reduced during aestivation. Similarly, sartorius dry muscle mass, water content and whole muscle CSA was significantly reduced during aestivation. Endogenous antioxidants were maintained at control levels throughout aestivation in all four muscles. The results suggest changes to muscle morphology during aestivation may occur when lipid reserves have been depleted and protein becomes the primary fuel substrate for preserving basal metabolic processes. Muscle atrophy as a result of this protein catabolism may be correlated with locomotor function, with smaller non-jumping muscles preferentially used as a protein source during fasting over larger jumping muscles. Higher levels of endogenous antioxidants in the jumping muscles may confer a protective advantage against oxidative damage during aestivation; however, it is not clear whether they play a role during aestivation or upon resumption of normal metabolic activity.

Key words: aestivation, antioxidants, morphometrics, muscle disuse atrophy, myofibre, oxidative damage, skeletal muscle, Cyclorana alboguttata

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