Luna Facundo, Antinuchi C Daniel
Laboratorio de Ecofisiología, Universidad Nacional de Mar del Plata, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), CC 1245, Mar del Plata, Argentina.
Comp Biochem Physiol A Mol Integr Physiol. 2007 Aug;147(4):948-54. doi: 10.1016/j.cbpa.2007.02.032. Epub 2007 Mar 6.
The low basal metabolic rate (BMR) observed in subterranean rodents, compared to that of surface-dwelling species of comparable size, has been proposed to be an adaptation to underground life. Two main hypotheses have been proposed to explain this finding, the cost of burrowing and the thermal stress. The former states that the low BMR is due to the high cost of extending the tunnel system whereas the other relates it to the possibility of overheating in burrows where evaporative and convective heat exchange are restricted. Additionally, both hypotheses related the energetics of subterranean rodent with spatial distribution. The genus Ctenomys is an excellent model to evaluate the cost of burrowing or thermal stress, since they are widely distributed, with members differing markedly in body mass. The aim of this study was to assess digging and basal energetics in two Ctenomys species that live in sympatry in a coastal grassland, but differ in their microspatial distribution by soil preference. We used the obtained energetic data to test both energy-distribution hypotheses. We measured BMR and digging metabolic rate (DMR) through open flow respirometry in two species exposed to soft and hard soils. In brief, DMR in Ctenomys talarum (100-170 g), as in Ctenomys australis (250-600 g), was unaffected by soil hardness. Within thermoneutral zone of each species, DMR/RMR quotient was lower in the smaller species. Our data did not support the thermal stress hypothesis, but the cost of burrowing hypothesis was not rejected. Other alternative hypotheses are proposed to explain the distribution of C. talarum and C. australis.
与同等体型的地表穴居物种相比，地下啮齿动物的基础代谢率较低，这被认为是对地下生活的一种适应。人们提出了两种主要假说来解释这一现象，即挖掘成本假说和热应激假说。前者认为低基础代谢率是由于扩展洞穴系统的成本高昂，而另一种假说则将其与洞穴中过热的可能性联系起来，因为在洞穴中蒸发和对流热交换受到限制。此外，这两种假说都将地下啮齿动物的能量学与空间分布联系起来。栉鼠属是评估挖掘成本或热应激的优秀模型，因为它们分布广泛，不同成员的体重差异显著。本研究的目的是评估两种栉鼠的挖掘和基础能量学，这两种栉鼠生活在沿海草原的同域环境中，但在土壤偏好上的微空间分布有所不同。我们利用获得的能量数据来检验这两种能量分布假说。我们通过开放式流动呼吸测定法测量了两种暴露于软土和硬土中的栉鼠的基础代谢率和挖掘代谢率。简而言之，塔拉栉鼠（100 - 170克）的挖掘代谢率与南方栉鼠（250 - 600克）一样，不受土壤硬度的影响。在每个物种的热中性区内，较小物种的挖掘代谢率与基础代谢率的比值较低。我们的数据不支持热应激假说，但挖掘成本假说未被否定。我们还提出了其他替代假说来解释塔拉栉鼠和南方栉鼠的分布。
