The tongue of chameleons and the Mount Lyell salamander accelerates at ballistic speeds even in cold weather using an elastic recoil mechanism.

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Tongue of the chameleon. Source: La morphologie du caméléon

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References

“The chameleon’s tongue moves at ballistic speeds – the acceleration reaches 50 g – five times more than an F16 fighter jet. The burst of speed is produced by spiral muscles in the tongue, which contract width-wise to make them stretch forward. A lubricant allows the muscles to slide at time-slicing speeds.” (Downer 2002:70)

Book
Weird Nature: An Astonishing Exploration of Nature's Strangest BehaviorMarch 2, 2002
John Downer

“Environmental temperature impacts the physical activity and ecology of ectothermic animals through its effects on muscle contractile physiology. Sprinting, swimming, and jumping performance of ectotherms decreases by at least 33% over a 10 °C drop, accompanied by a similar decline in muscle power. We propose that ballistic movements that are powered by recoil of elastic tissues are less thermally dependent than movements that rely on direct muscular power. We found that an elastically powered movement, ballistic tongue projection in chameleons, maintains high performance over a 20 °C range. Peak velocity and power decline by only 10%–19% with a 10 °C drop, compared to >42% for nonelastic, muscle-powered tongue retraction. These results indicate that the elastic recoil mechanism circumvents the constraints that low temperature imposes on muscle rate properties and thereby reduces the thermal dependence of tongue projection.” (Anderson & Deban 2010:5495)

Journal article
Ballistic tongue projection in chameleons maintains high performance at low temperatureProceedings of the National Academy of SciencesMarch 9, 2010
C. V. Anderson, S. M. Deban

Journal article
Cold-blooded snipers: thermal independence of ballistic tongue projection in the salamander Hydromantes platycephalusJournal of Experimental Zoology Part A: Ecological Genetics and PhysiologySeptember 28, 2011
Stephen M. Deban, Jason C. Richardson

“To capture prey, chameleons ballistically project their tongues as far as 1.5 body lengths with accelerations of up to 500 m s–2. At the core of a chameleon’s tongue is a cylindrical tongue skeleton surrounded by the accelerator muscle. The key structure in the projection mechanism is probably a cylindrical connective–tissue layer, which surrounds the entoglossal process… This tissue layer comprises at least 10 sheaths that envelop the entoglossal process. The outer portion connects anteriorly to the accelerator muscle and the inner portion to the retractor structures. The sheaths contain helical arrays of collagen fibres. Prior to projection, the sheaths are longitudinally loaded by the combined radial contraction and hydrostatic lengthening of the accelerator muscle, at an estimated mean power of 144 W kg–1 in C. melleri. Tongue projection is triggered as the accelerator muscle and the loaded portions of the sheaths start to slide over the tip of the entoglossal process. The springs relax radially while pushing off the rounded tip of the entoglossal process, making the elastic energy stored in the helical fibres available for a simultaneous forward acceleration of the tongue pad, accelerator muscle and retractor structures. The energy release continues as the multilayered spring slides over the tip of the smooth and lubricated entoglossal process… Thus, we have identified a unique catapult mechanism that is very different from standard engineering designs…” (de Groot & van Leeuwen 2004:761)

Journal article
Evidence for an elastic projection mechanism in the chameleon tongueProceedings of the Royal Society B: Biological SciencesApril 5, 2004
J. H. de Groot, J. L. van Leeuwen

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Learn More about the living system/s

Organism
Mount Lyell SalamanderHydromantes platycephalusSpecies


Organism
ChameleonChamaeleonidaeFamily


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