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Question Corner: How far and fast do chameleon tongues move?

A chameleon found lurking about next to the Papanasam dam in Tirunelveli.

A chameleon found lurking about next to the Papanasam dam in Tirunelveli.   | Photo Credit: A. Shaikmohideen

Previous studies have found that chameleons can ballistically project their tongues up to two body lengths. This is based on work done with large-sized chameleons. But using smaller chameleons, Christopher V. Anderson from the Department of Ecology and Evolutionary Biology at Brown University, U.S., found that smaller chameleons are able to project their tongues far longer. He reported his findings in 2016 in a paper published in the journal Scientific Reports. Using a chameleon species Rhampholeon spinosus, which is just 47 mm SVL (snout to vent length), he found tongue projection distances are as high as 2.5 body lengths. Tongue projections more than twice the body length was seen in three other species too, all of which are smaller than 90 mm SVL.

Dr. Anderson also found that both acceleration and mass-specific power increased as body size decreased. Using large chameleons, researchers had found earlier that chameleons project their tongues with peak accelerations of up to 486 metres per second. But using the R. spinosus species, he found peak accelerations as high as 2,590 metres per second, which is five times faster than that of the largest chameleon, and faster than any reptile, bird or mammal. This incredible acceleration is powered by 14 kW/kg muscle output.

Smaller chameleons are able to achieve this feat as they have evolved larger tongues relative to their body size. “Stretching elastic tissues and using their recoil to power movement allows organisms to release energy more rapidly than by muscle contraction directly, thus amplifying power output,” he says.

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Printable version | Aug 10, 2020 7:39:29 AM | https://www.thehindu.com/sci-tech/science/quicksilver-tongue/article32191902.ece

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