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Convergently evolved muscle architecture enables high-performance ballistic movement in salamanders
Jeffrey Scales1, Segall V Bloom2, Stephen M Deban3
1Department of Biological Sciences, One University Circle, California State University Stanislaus, Turlock, California.
Journal of Morphology
|December 29, 2019
Summary
Ballistic tongue projection in Plethodontidae salamanders evolved multiple times independently. This involved changes in the subarcualis rectus (SAR) muscle, favoring elastic power over muscle power for rapid tongue projection.
Area of Science:
- Evolutionary biology
- Biomechanics
- Vertebrate anatomy
Background:
- Elastically powered ballistic movements, like tongue projection, offer advantages such as increased speed and range.
- Both muscle-powered and elastically powered tongue projection exist within Plethodontidae salamanders.
Purpose of the Study:
- To investigate the evolutionary morphology of the subarcualis rectus (SAR) muscle in Plethodontidae, comparing elastically powered ballistic projection with muscle-powered projection.
- To understand how SAR morphology has evolved from muscle-powered to elastically powered systems.
Main Methods:
- Comparative morphological analysis of the subarcualis rectus (SAR) muscle across Plethodontidae species.
- Identification of key morphological traits associated with ballistic versus muscle-powered tongue projection.
Main Results:
- Two distinct SAR morphologies were identified: one facilitating elastic ballistic projection and another supporting muscle-powered projection.
- The ballistic SAR morphology evolved independently multiple times, characterized by increased collagen, larger muscles, and loss of inner myofiber attachment to the skeleton.
- The muscle-powered SAR morphology, similar to outgroup Salamandridae, retains inner myofiber attachment and has reduced collagen and smaller muscles.
Conclusions:
- The evolution of elastically powered ballistic tongue projection in Plethodontidae is a recurring theme, driven by correlated changes in SAR muscle morphology, particularly the loss of inner myofiber attachment.
- This convergent evolution towards a ballistic SAR morphology highlights functional adaptation for rapid movements.
- The retention of muscle-powered SAR morphology may reflect ancestral traits or specific feeding ecology adaptations.
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