Document Type

Article

Publication Date

March 2010

Keywords

biomechanics; muscle physiology, elastic storage, thermal ecology, Chamaeleonidae

Abstract

Environmental temperature impacts the physical activity and ecology of ectothermic animals through its effects onmuscle contractile physiology. Sprinting, swimming, and jumping performance of ecto-therms decreases by at least 33% over a 10 degrees C drop, accompanied by a similar decline inmuscle 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 degrees C range. Peak velocity and power decline by only 10%-19% with a 10 degrees 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. We propose that organisms that use elastic recoil mechanisms for ecologically important movements such as feeding and locomotion may benefit from an expanded thermal niche.

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