Department of Biological Sciences, Clemson University, Clemson, SC, USA.
Aquatic Toxicology Laboratory, St. Cloud State University, St. Cloud, MN, USA.
J Anat. 2020 Jun;236(6):1160-1166. doi: 10.1111/joa.13169. Epub 2020 Feb 24.
Assessing the factors that contribute to successful locomotor performance can provide critical insight into how animals survive in challenging habitats. Locomotion is powered by muscles, so that differences in the relative proportions of red (slow-oxidative) vs. white (fast-glycolytic) fibers can have significant implications for locomotor performance. We compared the relative proportions of axial red muscle fibers between groups of juveniles of the amphidromous gobiid fish, Sicyopterus stimpsoni, from the Hawaiian Islands. Juveniles of this species migrate from the ocean into freshwater streams, navigating through a gauntlet of predators that require rapid escape responses, before reaching waterfalls which must be climbed (using a slow, inching behavior) to reach adult breeding habitats. We found that fish from Kaua'i have a smaller proportion of red fibers in their tail muscles than fish from Hawai'i, matching expectations based on the longer pre-waterfall stream reaches of Kaua'i that could increase exposure to predators, making reduction of red muscle and increases in white muscle advantageous. However, no difference in red muscle proportions was identified between fish that were either successful or unsuccessful in scaling model waterfalls during laboratory climbing trials, suggesting that proportions of red muscle are near a localized fitness peak among Hawaiian individuals.
评估有助于成功运动表现的因素可以提供重要的见解，了解动物如何在具有挑战性的栖息地中生存。运动是由肌肉驱动的，因此红肌（慢氧化）与白肌（快糖酵解）纤维的相对比例的差异对运动表现有重大影响。我们比较了来自夏威夷群岛的洄游性虾虎鱼 Sicyopterus stimpsoni 的幼鱼群体之间的轴性红肌纤维的相对比例。该物种的幼鱼从海洋迁移到淡水溪流，在到达瀑布之前需要通过一系列的捕食者，这些捕食者需要快速的逃避反应，然后必须爬上瀑布（使用缓慢的、渐进的行为）才能到达成年繁殖栖息地。我们发现，来自考艾岛的鱼的尾巴肌肉中的红肌纤维比例比来自夏威夷岛的鱼小，这与考艾岛的瀑布前溪流更长的预期相符，这可能会增加与捕食者的接触，从而减少红肌和增加白肌是有利的。然而，在实验室攀爬试验中，成功或未能成功攀爬模型瀑布的鱼之间没有发现红肌比例的差异，这表明在夏威夷个体中，红肌比例接近局部适应峰值。
