Guillaume Olivier, Deluen Marine, Raffard Allan, Calvez Olivier, Trochet Audrey
Station d'Ecologie Théorique et Expérimentale UMR 5321 CNRS Université Paul Sabatier Moulis France.
Ecol Evol. 2020 Oct 12;10(23):12983-12989. doi: 10.1002/ece3.6882. eCollection 2020 Dec.
According to theories on cave adaptation, cave organisms are expected to develop a lower metabolic rate compared to surface organisms as an adaptation to food scarcity in the subterranean environments. To test this hypothesis, we compared the oxygen consumption rates of the surface and subterranean populations of a surface-dwelling species, the newt occasionally found in caves. In this study, we designed a new experimental setup in which animals with free movement were monitored for several days in a respirometer. First, we measured the metabolic rates of individuals from the surface and subterranean populations, both maintained for eight years in captivity in a natural cave. We then tested individuals from these populations immediately after they were caught and one year later while being maintained in the cave. We found that the surface individuals that acclimated to the cave significantly reduced their oxygen consumption, whereas individuals from the subterranean population maintained in the cave under a light/dark cycle did not significantly modify their metabolic rates. Second, we compared these metabolic rates to those of an obligate subterranean salamander (), a surface aquatic Urodel (), and a fish species () as references for surface organisms from different phyla. As predicted, we found differences between the subterranean and surface species, and the metabolic rates of surface and subterranean populations were between those of the obligate subterranean and surface species. These results suggest that the plasticity of the metabolism observed in surface was neither directly due to food availability in our experiments nor the light/dark conditions, but due to static temperatures. Moreover, we suggest that this adjustment of the metabolic level at a temperature close to the thermal optimum may further allow individual species to cope with the food limitations of the subterranean environment.
根据洞穴适应理论，与地表生物相比，洞穴生物预计会降低代谢率，以适应地下环境中的食物稀缺。为了验证这一假设，我们比较了一种偶尔在洞穴中发现的地表栖息物种——蝾螈的地表种群和地下种群的耗氧率。在本研究中，我们设计了一种新的实验装置，在呼吸计中对自由活动的动物进行了几天的监测。首先，我们测量了在天然洞穴中圈养八年的地表种群和地下种群个体的代谢率。然后，我们在捕获这些种群的个体后立即对其进行测试，并在将它们饲养在洞穴中一年后再次测试。我们发现，适应洞穴环境的地表个体显著降低了耗氧量，而在明暗循环条件下饲养在洞穴中的地下种群个体的代谢率没有显著变化。其次，我们将这些代谢率与一种专性地下蝾螈、一种地表水生有尾目动物和一种鱼类的代谢率进行了比较，作为不同门的地表生物的参考。正如预期的那样，我们发现地下物种和地表物种之间存在差异，地表种群和地下种群的代谢率介于专性地下物种和地表物种之间。这些结果表明，在我们的实验中，地表蝾螈观察到的代谢可塑性既不是直接由于食物供应，也不是由于明暗条件，而是由于静态温度。此外，我们认为，在接近最适温度的温度下对代谢水平的这种调节可能进一步使个体物种能够应对地下环境中的食物限制。
