与生物体的环境需求相匹配的适当的肌肉功能和肌肉纤维结构对于它们在任何生态系统中的成功至关重要。墨西哥洞穴鱼,墨西哥Astyanax,有两种形态:一种居住在隔热洞穴中的专性洞穴居住形式和O2差的环境,和生活在更热变量中的表面形式,但O2丰富的河流环境。因为环境可以决定生理适应,比较该物种两种形态类型中白肌代谢的有氧和无氧代谢谱是有意义的,以及它们的肌肉结构。这里,我们使用两种形态型的墨西哥洞穴鱼的白肌肉来确定柠檬酸合酶(CS)活性作为有氧潜能的量度,和乳酸浓度作为三种不同慢性适应温度(14°C,25°C,和31°C)。通过检查两种形态的有氧和无氧潜能,我们试图将环境热灵活性与肌肉代谢联系起来。我们发现表面形态型具有较高的CS活性和较低的乳酸浓度,表明有氧代谢的整体使用更有效;而洞穴形态型显示较低的CS活性和较高的乳酸浓度,表明对厌氧途径的更强依赖。我们还测量了先前与整个动物代谢有关的白肌肉组织学变量:纤维直径,在25°C下,两种形态的每毫米纤维和肌核结构域(MND)的核数,以检查肌肉形态的细胞水平差异。然而,我们发现纤维直径没有差异,两种形态之间每毫米纤维或MND的核数。因此,尽管这些物种的细胞形态相似,两种形态进化的环境差异导致了它们代谢谱的差异。
Proper muscle function and muscle fiber structures that match the environmental demands of organisms are imperative to their success in any ecosystem. The Mexican cavefish, Astyanax mexicanus, has two morphotypes: an obligate cave-dwelling form that lives in thermally insulated caves and an O2 poor environment, and a surface form that lives in a more thermally variable, but O2 rich river environment. As environment can determine physiological adaptations, it is of interest to compare the aerobic and anaerobic metabolic profiles of white muscle metabolism in both morphotypes of this species, as well as their muscle structures. Here, we used white muscle of both morphotypes of the Mexican cavefish to determine citrate synthase (CS) activity as a measure of aerobic potential, and lactate concentration as a measure of anaerobic potential at three different chronic acclimation temperatures (14°C, 25°C, and 31°C). By examining aerobic and anaerobic potential in both morphs, we sought to link environmental thermal flexibility to muscle metabolism. We found that the surface morphotype had higher CS activity and lower lactate concentration, suggesting an overall more efficient usage of aerobic metabolism; whereas the cave morphotype showed lower CS activity and higher lactate concentration, suggesting a stronger reliance on anaerobic pathways. We also measured white muscle histological variables that have been previously linked to whole-animal metabolism: fiber diameter, number of nuclei per mm of fiber and myonuclear domain (MND) of both morphotypes at 25°C to examine cell-level differences in muscle morphology. However, we found no differences in fiber diameter, number of nuclei per mm of fiber or MND between the two morphotypes. Thus, although the cellular morphology is similar in these species, the environmental differences in the evolution of the two morphs has led to differences in their metabolic profiles.