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The Oddities of the Chameleon - The Tongue

By Ken Kalisch


Citation:

Kalisch, K. (2003). The Oddities of the Chameleon - The Tongue. Chameleons! Online E-Zine, July 2003. (http://www.chameleonnews.com/03JulKalischTongue.html)


Much of the attraction we have to the chameleon is its' unique physical capabilities it has developed in its' adaptation to the world in which it lives. This includes the unique feature of how it captures its' prey using its' tongue.

The chameleon's tongue doesn't just pop out from the reptile's mouth but is ejected with a strong force as though spring-loaded. The U-shaped hyoid bone acts as an integral part to facilitate the action as a lever in assisting to eject the tongue. Because the action is less powerful when the prey is closer, chameleons will oftentimes back up before releasing the tongue to generate the intense force needed to snatch a meal. The total time necessary for the tongue to be ejected is under one-sixteenth of a second.

The complete structure of the chameleons' tongue is a symphony of musculature and bone (cartilage). The combination of the two, combined with their independently functioning eyes, create a force most insects fail to escape. The tongue, which is hollow, is covering a horn shaped piece of tapering cartilage called the hyoid horn. This is attached to the center of the U-shaped hyoid bone and it is the means, via muscular contractions, that the tongue is pushed out of the chameleons' mouth and onto the unsuspecting insect. The accelerator muscles or ring muscles are used to contract against the hyoid horn. The contractions combined with the tapering of the horn create a squeezed forward thrust that ejects the tongue forward and out of the mouth. When at rest, the entire structure rests easily at the bottom of the chameleons' throat and mouth.



















The tip of the tongue is a textured mass that assists in the capture of the prey along with the use of the sticky saliva; the tip has a small flap that actually wraps partially around the prey further assisting in securing the insect. So when the chameleon is going to shoot at a insect all these muscles come into an orchestrated play that results in the shooting of the tongue, capture of the prey and the return of the insect to the chameleons' mouth. Not bad in less than one-quarter of a second.

The muscles that compose these structures have two basic functions. The fast "super-contraction" or accelerator muscle for catching prey and normal retraction muscles for reeling it back once it has been captured. Chameleons can catch food-prey from a distance as far away as more than two and a half times their body lengths. The action is possible because the reptiles' tongues have powerful "super-contracting" muscles that are unique among back-boned animals, a team of researchers explains in the Journal of Experimental Biology.

Researcher Anthony Herrel of the University of Antwerp, Belgium, has co-author a report on the chameleon's tongue and its special muscles. He theorizes the organ may have become specialized so that chameleons, which sit and wait for food, so they can maximize the limited mealtime opportunities by capturing not only insects but to even include birds for the larger chameleon species.

The studies were done using two chameleon species Chamaeleo calyptratus and Furcifer oustaletti. Herrel and his colleagues experimented by positioning crickets at various distances from the chameleons' mouth. The chameleons were about 4.7 inches (12 centimeters) long and the insects were placed from 2 to 12 inches (5 to 30 centimeters) away.

The chameleons generated enough strength in their tongues to snatch the prey and snap their tongues back, which would be quite a feat for normal muscles. The researchers found, that the action was possible because the chameleons' tongue muscles contain unusual filaments that allow for a "super-contraction."

This is the first time this unique muscle mechanism has been found to be exhibited in a vertebrate according to the researchers. It has been previously observed in insects.

Observing Chameleons feeding, most everyone marvels at the dexterity and accuracy of their tongues. The process always evokes an AAAH or ooooh! It is a truly amazing event to observe. Hopefully this article will help you to have a better understanding of all that goes on to allow that tongue to do what it does!

Aren't chameleons amazing! Once again, they seem to of have their very own unique way of doing things.


Ken Kalisch


Ken Kalisch has worked with over 40 species of chameleons in the last decade. He was co-editor of the Chameleon information Network, as well as being published by Advanced Vivarium Systems dealing with his experience breeding Calumma parsonii parsonii in captivity. He was the editor of this CHAMELEONS! EZine from March 2002-March 2004.





 

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