Cold-blooded snipers: thermal independence of ballistic tongue projection in the salamander Hydromantes platycephalus

J Exp Zool A Ecol Genet Physiol. 2011 Dec 1;315(10):618-30. doi: 10.1002/jez.708. Epub 2011 Sep 26.


Plethodontid salamanders of the genus Hydromantes capture prey using the most extreme tongue projection among salamanders, and can shoot the tongue a distance of 80% of body length in less than 20 msec. The tongue skeleton is projected from the body via an elastic-recoil mechanism that decouples muscle contraction from tongue projection, amplifying muscle power tenfold. We tested the hypothesis that the elastic-recoil mechanism also endows tongue projection with low thermal dependence by examining the kinematics and dynamics of tongue projection in Hydromantes platycephalus over a range of body temperatures (2-24°C). We found that H. platycephalus maintained tongue-projection performance over the tested temperature range and that tongue projection showed thermal independence (Q(10) values of 0.94-1.04) of all performance parameters including projection distance, average velocity, and peak instantaneous values of velocity, acceleration, and power. Nonelastic, muscle-powered tongue retraction, in contrast, responded to temperature changes significantly differently than elastic tongue projection; performance parameters of retraction displayed thermal dependence typical of muscle-powered movement (Q(10) values of 1.63-4.97). These results reveal that the elastic-recoil mechanism liberates tongue projection from the effects of temperature on muscle contractile rates. We suggest that relative thermal independence is a general characteristic of elastic-recoil mechanisms and may promote the evolution of these mechanisms in ectothermic animals.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biological Evolution
  • Biomechanical Phenomena
  • Body Temperature*
  • Electromyography
  • Feeding Behavior / physiology*
  • Muscle Contraction / physiology
  • Predatory Behavior / physiology*
  • Tongue / physiology*
  • Urodela / physiology*
  • Video Recording