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Tokay gecko 'tear here' echo

By-Omkar Singh,Administrator Science Relief

Tokay gecko on log

Research which appeared yesterday in the open access journal PLoS ONE suggests that the biological microstructures present in a gecko’s tail are responsible for the animal’s ability to voluntarily shed it when in danger. The team from Aarhus University in Denmark used various proteomics and bio-imaging techniques to elucidate the morphology of the lizard’s tail in detail and found that it is, to all intents and purposes, pre-severed.

‘Autotomy’ refers to the effective self-amputation of various appendages by animals, usually as a mechanism to defend against predators. The voluntary shedding mechanism is especially common among lizards, but also occurs in other species such as crabs, brittle stars, spiders and octopuses. The team involved in this study looked specifically at tail, or caudal, autotomy as it occurs in the Tokay gecko (Gekko gecko). 

Lead author of the paper Professor Jan J Enghild, from the Department of Molecular Biology and Genetics at Aarhus University, offered ScienceOmega.com his perspective on the research findings. It was a general interest in nature and how it works that motivated the investigation, according to Professor Enghild.

"I have been interested in extracellular matrix degradation for many years, and originally thought that proteases would be involved," he said.

The extracellular matrix is the mesh of proteins and proteoglycans – often consisting mainly of collagen – which support the cells and hold them in place. It is difficult for cells to move or separate in this network of fibres; when they are required to do so, the matrix must be degraded by protein-splitting enzymes – proteases. Although the paper acknowledges that the role of proteolytic enzymes in the process of tail autotomy cannot be discounted completely, these enzymes and their fragments were conspicuous by their absence in the analysis conducted, indicating that the process is protease-independent.

The bio-imaging techniques used included magnetic resonance imaging (MRI) and scanning electron microscopy (SEM). These approaches can produce images of much higher resolution than it was previously possible to obtain, allowing the researchers to generate the ideas presented in the paper.

The images clearly illustrate the wedge-shaped muscle extensions at the fracture point of the tail, with minute mushroom-shaped structures visible at the ends of the muscle fibres. The paper hypothesises that the mushroom-shape is most likely assumed during autotomy as a way of reducing adhesion rather than being present pre-shedding. Interdigitation (like interlocking fingers) of the muscles and tail segments provides a greater surface area for increased adhesion, while horizontal fracture planes penetrate all the way through the tissue of the tail, enabling quick and easy release in response to the threat of predation.

"The mechanism turned out to be more of a ‘mechanical’ event, where the tail was already severed and the lizard able to relapse it by use of muscle contractions," Professor Enghild explained.

It is likely that the same structures and mechanism enable autotomy in all lizards, but whether it works in the same way in other species is a matter of speculation. The fact that the structural integrity of the gecko’s tail is maintained until it is necessary to detach it means that there is the potential for the structures and mechanisms involved to prove useful in other fields, as Professor Enghild outlined.

"The biological structures observed in the gecko facilitate a very fast transition that might inspire structural engineers and material scientists interested in making quickly detachable structures."
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Posted by Omkarr singh on Friday, January 04, 2013. Filed under . You can follow any responses to this entry through the RSS 2.0

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