Extreme Performance at Low Temperature: Ballistic Tongue Projection in Salamanders and Chameleons

环境温度对动物的生理过程有深远的影响，这些动物的体温是由周围环境决定的，如爬行动物和两栖动物。这类动物在低温下活动的能力受到肌肉收缩速度等生理过程放缓的限制。火蜥蜴和变色龙的弹道舌头突起的爆炸性运动在广泛的温度范围内保持极高的性能方面是不寻常的。这项研究将考察赋予这种高性能和温度不敏感度的生理和生物力学过程。舌头投射的动力来自于胶原蛋白肌腱状结构的快速弹性回缩(以一种“弓和箭”的机制)，它将运动的动力从肌肉收缩的动力中解放出来。这一机制可能赋予该系统和其他肌肉骨骼系统扩展的高性能热宽度，因为胶原蛋白的弹性回弹比肌肉收缩速度和功率对温度的敏感性低得多。这项研究将使用高速数字成像和记录舌头投射过程中的肌肉激活模式，并测量肌肉收缩的速度和力量，每种测量都在一定的温度范围内。合并后的数据将使这一弹性后坐模型能够进行稳健的测试，而来自两个独立进化的系统--火蜥蜴和变色龙--的数据将允许测试该模型的通用性和预测能力。这些结果将进一步加深我们对环境、生物力学和生理学之间复杂相互作用的理解，这些都不能从基本原理中自信地预测出来。研究结果还将对具有弹性成分的不同生物系统的热响应提供可测试的预测。舌头投射是一种非常吸引人和有效的工具，用于交流生理学和生物力学方面的发现，并且是在科学研究的各个方面招募和培训学生的理想选择。这一结果也可能在假肢和运动器材的设计中具有实际应用，这些装置和运动器材可以改善肌肉的性能和功能范围。

Environmental temperature has profound effects on the physiological processes of animals whose body temperature is determined by their surroundings, such as reptiles and amphibians. The ability of such animals to be active at low temperatures is limited by the slowing of physiological processes such as the speed of muscle contraction. The explosive movements of ballistic tongue projection in salamanders and chameleons are unusual in maintaining extremely high performance across a broad range of temperatures. This study will examine the physiological and biomechanical processes that confer this high performance and temperature insensitivity. Tongue projection is powered by rapid elastic recoil of collagen tendon-like structures (in a "bow and arrow" mechanism) which frees the dynamics of the movement from the dynamics of muscle contraction. This mechanism may endow this system and other musculoskeletal systems with an expanded thermal breadth of high performance, because the elastic recoil of collagen has a much lower temperature sensitivity than muscle contraction speed and power. This study will use high-speed digital imaging and recordings of muscle activation patterns during tongue projection, and measurements of the speed and power of muscle contractions, each at a range of temperatures. The combined data will enable a robust test of this elastic recoil model, and data from two independently evolved systems -salamanders and chameleons - will permit a test of the model's generality and predictive power. The results will further our understanding of the complex interplay of environment, biomechanics and physiology, which cannot be confidently predicted from first principles. Results will also provide testable predictions about the thermal responses of diverse biological systems with elastic components. Tongue projection is a highly engaging and effective vehicle for communicating discoveries in physiology and biomechanics, and is ideal for recruiting and training students in all aspects of scientific research. The results may also have practical applications in the design of prosthetic devices and sports equipment that improve performance and the functional range of muscles.