RUI: Does Maintenance of Elevated Muscle Temperatures in Tunas Result in Increased Swimming Performance?

除了成为世界各地重要商业渔业的焦点外，金枪鱼是生物学家特别感兴趣的，因为它们是唯一已知的通过代谢产生的热量来维持肌肉温度（Tm）显着高于其环境温度的硬骨鱼类；也就是说，它们是吸热的。为了做到这一点，金枪鱼需要热源（通过连续游泳时红肌肉的收缩提供）和在活动时将热量保留在肌肉内的机制（作为逆流热交换器的血管）。本研究项目的目的是验证金枪鱼保持高肌肉温度会提高游泳表现的假设。一个计算机化的、温度控制的、可变速度的游泳隧道呼吸计系统将用于测量幼黑鲣鱼的最大可持续/有氧游泳速度与鱼的大小之间的关系，以及游泳成本与鱼的大小之间的关系，其叉长（FL）从~100毫米到~250毫米。这些尺寸在最近由首席研究员发表的一篇文章中假设的恒温动物最小尺寸207毫米FL以上和以下。将与相似尺寸范围的密切相关的鱼类进行比较，这些鱼类在任何尺寸下都不能显著提高Tm以“控制”鱼类尺寸的影响。同样，如果游泳模式随着鱼的大小而改变，那么最大速度和/或游泳成本可能与Tm无关。因此，将利用计算机视频运动分析系统，从每条鱼以最高速度游泳的高速录像带中确定游泳模式，以及尾巴跳动的频率和幅度。此外，将在实验室水族箱和呼吸计中测量幼黑鲣鱼游动时的Tm大小范围。这些数据，结合对同一条鱼的热交换器血管形态和红肌量的显微镜检查，将使PI能够验证黑色千吨车中最小恒温动物尺寸为207毫米FL的假设。这些研究将极大地有助于我们理解恒温动物的进化及其所带来的优势。这一结果将对金枪鱼的生态学、能量学以及短期和长期运动产生影响。此外，在提案研究中获得的游泳成本估计数可用于金枪鱼能量学和种群动态模型，用于管制这些物种的渔业方面。* * *

9318065 Dickson In addition to being the focus of important commercial fisheries throughout the world, tunas are of particular interest to biologists because they are the only bony fishes known to maintain muscle temperatures(Tm) elevated significantly above the temperature of their environment by using metabolically derived heat; i.e., they are endothermic. To do so, tunas need a source of heat (provided by contraction of red muscle during continuous swimming) and a mechanism to retain the heat within the muscle during activity (blood vessels arranged as counter-current heat exchangers). The goal of this research project is to test the hypothesis that maintenance of high muscle temperatures in tunas results in increased swimming performance. A computerized, temperature-controlled, variable speed, swimming-tunnel respirometer system will be used to measure the maximal sustainable/aerobic swimming speed versus fish size and the cost of swimming versus fish size relationships for juvenile black skipjack tunas ranging in fork length (FL) from ~100mm to ~250mm. These sizes are above and below the minimum size for endothermy of 207 mm FL postulated in a recent publication by the Principal Investigator. Comparisons will be made with a similar size range of closely related fishes that cannot elevate Tm significantly at any size to "control" for the effects of fish size. Also, if swimming mode changes with fish size, the maximal speed and/or cost of swimming may change independent of Tm. Therefore, swimming mode, as well as tail beat frequencies and amplitudes, will be determined from high-speed videotape recordings of each fish swimming at speeds up to its maximum, using a computerized video motion analysis system. In addition, Tm in a size range of juvenile black skipjack tuna will be measured as they swim in laboratory aquaria and in the respirometer: these data, combined with microscopic examination of heat exchanger blood vessel morphology and red muscle amou nt in the same fish, will allows the PI to test the hypothesis that the minimum size for endothermy in black skip jacks is 207 mm FL. These studies will contribute a great deal to our understanding of the evolution of endothermy and the advantages it confers. The results will have implications for the ecology, energetics, and both short- and long-range movements of tunas. In addition, estimates of the cost of swimming obtained in the proposal study can be used in models of tuna energetics and population dynamics that are used to regulate the fishery aspects of these species. ***