Collaborative Research: The Functional Significance of Divergent Locomotor Muscle Designs In High Performance Fishes

该奖项支持对一个大型远洋鲨鱼家族--长尾鲨(Alopiidae)--的运动肌功能和设计进行调查和比较。所有的长尾鲨都很容易被它们长长的尾鳍识别出来，尾鳍既可以产生向前推力，也可以捕获猎物。然而，最近的研究表明，普通短尾鲨(Alopias Vocpinus)的游泳肌结构和血管布局都令人惊讶地不同于其他两个物种(大眼短尾鲨和远洋短尾鲨)。在普通脱粒机中，红色的有氧运动肌(RM)被浓缩成一个实心的活塞状肌块，主要分布在身体前部的中间位置(即靠近脊柱)。普通门限器与其他两个物种的不同之处还在于，通过一组侧支血管向右室提供血管供应，从而产生逆流热交换系统。这种热交换系统允许RM保存新陈代谢产生的热量，并比环境温度(即区域吸热)更热。Alopiidae是目前已知的唯一既具有吸热类群又具有放热类群的类群，是检验关于发散运动机制进化假说的理想系统。研究人员将对这三种斑鲨的游泳生物力学和运动学、热生理学和代谢生化进行检测。特别是，实验旨在确定普通长尾鲨在稳定游泳过程中运动肌肉的功能，并评估在一组密切相关的鲨鱼中运动系统的分歧程度。此外，金枪鱼、羊驼和普通脱毛鱼在RM形态上的惊人相似也为开展比较研究提供了一个合适的平台，以评估这三个群体在游泳机械设计上的趋同程度。这个项目的学术价值来自于与一群鲜为人知的鲨鱼合作并收集它们游泳生物力学、热生理学、肌肉腱适应和运动肌肉收缩功能的数据的前所未有的机会。这项拟议的工作将加深人们对选择性压力如何在短尾鲨体内塑造两个不同的肌肉系统，以及这些压力如何影响这一鲜为人知的群体的生态和生物学的理解。这项工作的更广泛影响包括代表不足的少数群体科学家的参与，对本科生和研究生的培训，开发一个传播研究成果的网站，以及与商业渔民合作和接触。

This award supports investigations and comparisons of locomotor muscle function and design within a single family of large pelagic sharks, the thresher sharks (Alopiidae). All thresher sharks are easily recognized by their very long caudal fin, which serves for both forward thrust production and prey capture, however, recent work has shown that both the architecture of the swimming muscles and the vascular layout of the common thresher (Alopias vulpinus) is surprisingly distinct from that of the other two species (bigeye thresher, A. superciliosus, and pelagic thresher, A. pelagicus). In the common thresher the red, aerobic locomotor muscle (RM) is condensed into a solid piston-like muscle mass that is predominantly distributed over the anterior body in a medial position (i.e., near the vertebral column). Common threshers also differ from the other two species in having a vascular supply to the RM through a set of lateral vessels that give rise to a counter current heat exchange system. This heat exchange system allows the RM to conserve metabolically produced heat and be warmer than ambient temperature (i.e., regional endothermy). The Alopiidae is the only group known to possess both regionally endothermic and ectothermic taxa, and constitutes the ideal system for testing hypotheses on the evolution of divergent locomotor mechanisms. The researchers will examine the swimming biomechanics and kinematics, thermal physiology, and metabolic biochemistry in the three alopiid sharks. In particular, experiments are designed to determine how the locomotor muscles in the common thresher shark function during steady swimming, and to assess the degree to which the locomotor systems have diverged within a single group of closely-related sharks. Further, the striking similarities in RM morphology between tunas, lamnids, and the common thresher also provide an opportune platform for launching comparative studies that assess the degree to which all three of these groups have converged on a similar mechanical design for swimming. The intellectual merits of this project arise from the unprecedented opportunity to work with a poorly understood group of sharks and collect data on their swimming biomechanics, thermal physiology, musculotendinous adaptations, and the locomotor muscle contractile function. The proposed work will increase the understanding of how selective pressures may have sculpted two divergent muscle systems within the threshers sharks and how these pressures have affected the ecology and biology of this poorly understood group. The broader impacts of this work include participation of under-represented minority scientists, training of undergraduate and graduate students, development of a website for dissemination of research findings, and collaboration with, and outreach to commercial fishermen.