AFTER a century of debate, biologists have figured out how a chameleon shoots its tongue out at lightning speed to snare its prey. The secret is a spring-loading mechanism that stores up energy like the elastic of a catapult prior to release.
Traditional theories about chameleons鈥� tongues suggested that 鈥渁ccelerator muscle鈥� in the outer layers of the tongue powers the process. That idea has prevailed for a century. Not convinced that this was the whole story, Johan van Leeuwen of the University of Wageningen and Jurriaan de Groot of Leiden University in the Netherlands painstakingly analysed slow-motion video footage of chameleons lapping up lunch, and tried matching this up with the tongue鈥檚 anatomy.
They deduced that the energy for the speedy lick comes from parts of the tongue called the intralingual sheathes, which wrap around bones running along the core of the tongue and are in turn sheathed by the accelerator muscle. The team found that 200 milliseconds before its tongue strikes, a chameleon uses the accelerator muscle to spring-load energy into the intralingual sheathes, packing them into one another like sections of a telescope. When the chameleon strikes, the pent-up energy can be released in just 20 milliseconds, accelerating the tongue pad forward at up to 50 g (Proceedings of the Royal Society B, DOI: 10.1098/rspb.2003.2637).
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