POWRE: A New Method to Test Hypotheses about the Development and Evolution of Endothermy in Tunas: Pilot study

这个POWRE项目将为PI提供所需的资源，使其能够采用一种技术来测量跨内线粒体膜的质子“泄漏”，作为衡量组织热产生的指标，以用于她建立的金枪鱼吸热系统的发展和进化的研究系统。在1999年夏天(POWRE资助开始之前)，PI将在马丁·布兰德博士的实验室学习这项技术(由NIH拨款资助)。POWRE拨款将使PI能够在国内机构建立这项技术，并与本科生合作者一起在那里对几种鱼类进行试点研究，以检验吸热性鱼类有更高的质子渗漏穿过生热组织(红色肌肉)内线粒体膜的假设。这些测试将包括将金枪鱼与它们的温热姊妹类群(长吻鳕鱼和东太平洋鳄鱼)进行比较，并将mako鲨与温性鲨鱼进行比较。如果这一假说得到支持，由此导致的组织产热率的提高将与金枪鱼标准代谢率的提高相对应(想必在Makos中也是如此)。未来的研究将检验两个假设：(1)线粒体质子泄漏的变化是吸热进化的重要一步；这将涉及基于系统发育的一些物种和额外的外温姐妹类群的比较。(2)随着幼金枪鱼在100-300 mm叉长范围内的缓慢抽动、氧化运动肌肉(红色肌肉)中形成维持高温的能力，该组织的产热率通过增加跨内线粒体膜的质子泄漏速率而增加。POWRE基金将允许PI探索一种新的研究方法，并通过更直接地测试金枪鱼和黑鲨的产热组织的独特特征，将其应用于推动该领域的发展。

This POWRE project will provide the resources needed for the PI to adapt a technique to measure proton "leak" across the inner mitochondrial membrane as a measure of tissue heat production to her established study system of the development and evolution of endothermy in tunas. During the summer of 1999 (prior to the start of POWRE funding), the PI will learn the technique in the lab of Dr. Martin Brand (funded by an NIH grant). The POWRE grant will enable the PI to establish the technique at the home institution and to conduct pilot studies there on several fish species, with undergraduate student collaborators, to test the hypothesis that endothermic fishes have an elevated rate of proton leak across the inner mitochondrial membrane of the thermogenic tissue (red muscle). These tests will involve comparisons of tunas with their ectothermic sister taxa (chub mackerel and eastern Pacific bonito), and of the mako shark with ectothermic sharks. If the hypothesis is supported, the resultant elevation in tissue heat-production rate would correspond to the elevated standard or "maintenance" metabolic rates of tunas (and presumably in makos). Future studies will test two hypotheses: (1) that the change in mitochondrial proton leak was an important step in the evolution of endothermy; this will involve phylogenetically based comparisons of a number of species and additional ectothermic sister taxa. (2) As juvenile tunas develop the capacity to maintain elevated temperatures in their slow-twitch, oxidative locomotor muscle (red myotomal muscle) across the size range of 100-300 mm fork length (FL), the heat production rate of this tissue is increased by increasing the rate of proton leak across the inner mitochondrial membrane. POWRE funding will allow the PI to explore a new research approach and apply it to advance the field by more directly testing for unique features of the thermogenic tissue in tunas and the mako shark.