Evolution of a functionally robust, high-performance musculoskeletal system

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Environmental temperature has strong effects on the physiological processes of animals such as amphibians whose body temperature is determined by their surroundings. Activity of such ectothermic animals is limited by the slowing of physiological processes at low temperatures, notably the speed and power of muscle contraction. In contrast to the thermal sensitivity of muscle-powered movements, the ballistic feeding movements of some ectothermic animals are scarcely affected by environmental temperature. Performance is maintained at a high level across a broad range of temperatures by virtue of an elastic-recoil mechanism. This 'bow and arrow' mechanism allows muscles to contract slowly and stretch tendon-like structures, which subsequently recoil rapidly to power movement. Because the speed of elastic recoil of collagen has a much lower temperature sensitivity than the speed of muscle contraction, such elastically powered movements display greater thermal robustness, potentially expanding the animal's thermal range. This research will examine the physiological basis for the evolution of high performance and thermal robustness in elastically powered movements. The research will focus on evolutionary transitions in performance of the integrated system as well as in the underlying motor control, morphology, biomechanics, and muscle contractile physiology. This study will also test the hypothesis that elastic systems evolve from non-elastic systems via the modification of existing anatomical structures rather than through fundamental changes in muscle physiology. A generalized model of elastic recoil will be applied to a focal ectothermic system--ballistic feeding in salamanders--in which extreme performance and thermal robustness have evolved multiple times in parallel. The research will make testable predictions about the robustness to environmental challenges of other diverse musculoskeletal systems with and without elastic components. Graduate, undergraduate and postdoctoral students will be trained in a wide range of scientific skills and activities, including field and laboratory procedures, participation at scientific meetings, and dissemination of results. An interactive online simulation of an elastic system (ballistic feeding in a salamander) will be developed to be used in teaching and by laypersons. Partnership with local K-12 teachers and a biology professor in Mexico will provide training as well as laboratory and field experiences to US and Mexican researchers, teachers and students. Research experiences for teachers will enhance the development of K-12 science educators and support the delivery of new research findings in a cross-curricular framework to classrooms in a large and diverse school district.