Tattersall Glenn J, Leite Cleo A C, Sanders Colin E, Cadena Viviana, Andrade Denis V, Abe Augusto S, Milsom William K
Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada.; National Institute of Science and Technology in Comparative Physiology (INCT-Fisiologia Comparada), 13505-060 Rio Claro, São Paulo, Brazil.
National Institute of Science and Technology in Comparative Physiology (INCT-Fisiologia Comparada), 13505-060 Rio Claro, São Paulo, Brazil.; Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil.
Sci Adv. 2016 Jan 22;2(1):e1500951. doi: 10.1126/sciadv.1500951. eCollection 2016 Jan.
With some notable exceptions, small ectothermic vertebrates are incapable of endogenously sustaining a body temperature substantially above ambient temperature. This view was challenged by our observations of nighttime body temperatures sustained well above ambient (up to 10°C) during the reproductive season in tegu lizards (~2 kg). This led us to hypothesize that tegus have an enhanced capacity to augment heat production and heat conservation. Increased metabolic rates and decreased thermal conductance are the same mechanisms involved in body temperature regulation in those vertebrates traditionally acknowledged as "true endotherms": the birds and mammals. The appreciation that a modern ectotherm the size of the earliest mammals can sustain an elevated body temperature through metabolic rates approaching that of endotherms enlightens the debate over endothermy origins, providing support for the parental care model of endothermy, but not for the assimilation capacity model of endothermy. It also indicates that, contrary to prevailing notions, ectotherms can engage in facultative endothermy, providing a physiological analog in the evolutionary transition to true endothermy.
除了一些显著的例外情况，小型变温脊椎动物无法通过内源性方式维持显著高于环境温度的体温。我们对鬃狮蜥（约2千克）繁殖季节夜间体温的观察结果对这一观点提出了挑战，其夜间体温维持在远高于环境温度的水平（高达10°C）。这使我们推测，鬃狮蜥增强了产热和保温的能力。代谢率增加和热传导降低是传统上被认为是“真正恒温动物”的鸟类和哺乳动物体温调节所涉及的相同机制。认识到一种体型与最早的哺乳动物相当的现代变温动物能够通过接近恒温动物的代谢率来维持升高的体温，这为关于恒温起源的争论提供了启示，支持了恒温起源的亲代抚育模型，但不支持恒温起源的同化能力模型。这也表明，与普遍观点相反，变温动物可以进行兼性恒温，这为向真正恒温动物的进化过渡提供了一种生理类似物。
