Crabs change leg muscles to prepare for migration

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Imagine spending months as a couch potato and then getting up to finish a marathon. This is essentially what Christmas Island red crabs (Gecarcoidea natalis) do when they undertake their famous migrations to breed.

A team of UK scientists has found that the crabs literally change their leg muscles in preparation for this arduous journey, publishing the results of their research in a recent issue of the Journal of Experimental Biology.

The red crabs spend the dry season safely ensconced in their burrows, rarely venturing out for more than ten minutes a day.  With the arrival of the monsoons, the crabs undertake a marathon journey lasting up to five days and travelling for up to 12 hours a day to reach their spawning grounds at the beaches.

Ute Postel and colleagues from the University of Bristol studied the transformation in the leg muscles of these crabs to enable them to undertake the long trek after months of relative inactivity.

Taking samples from muscle tissue of crabs from the dry season and the monsoon, the authors studied the mRNA (the molecule that is transcribed from genes and translated to make proteins) from the muscles to see if differences existed in the genes being transcribed in the muscles during the monsoon and non-monsoon periods.

The authors found that the leg muscles of the crabs during the monsoon period were transcribing more muscle protein and the versions of the genes they were transcribing made the leg muscles aerobic, high-endurance and resistant to fatigue while the genes transcribed during the non-monsoon made the leg muscles of the crabs anaerobic and suitable only for sprinting.

Tragically, Steve Morris, the author that initiated the study, would not live to see the publication of his work, being killed in a road accident in August 2009 before the paper was accepted for publication.

For more information, see the paper: Postel, U, F Thompson, G Barker, M Viney and S Morris (2010) Migration-related changes in gene expression in leg muscle of the Christmas Island red crab Gecarcoidea natalis: seasonal preparation for long-distance walking. Journal of Experimental Biology 213, pp. 1740–1750.