title: Seasonal reproductive endothermy in tegu lizards.
abstract: 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.
authors: 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.
authors: Glenn J
authors: GJ
authors: Tattersall
authors: 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.
authors: Cleo A C
authors: CA
authors: Leite
authors: Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil.
authors: Colin E
authors: 0000-0002-7627-4281
authors: CE
authors: Sanders
authors: Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada.
authors: Viviana
authors: V
authors: Cadena
authors: National Institute of Science and Technology in Comparative Physiology (INCT-Fisiologia Comparada), 13505-060 Rio Claro, São Paulo, Brazil.; Department of Zoology, São Paulo State University (UNESP), 13506-900 Rio Claro, Brazil.
authors: Denis V
authors: 0000-0002-7662-2848
authors: DV
authors: Andrade
authors: National Institute of Science and Technology in Comparative Physiology (INCT-Fisiologia Comparada), 13505-060 Rio Claro, São Paulo, Brazil.; Department of Zoology, São Paulo State University (UNESP), 13506-900 Rio Claro, Brazil.
authors: Augusto S
authors: 0000-0002-6765-8726
authors: AS
authors: Abe
authors: National Institute of Science and Technology in Comparative Physiology (INCT-Fisiologia Comparada), 13505-060 Rio Claro, São Paulo, Brazil.; Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada.
authors: William K
authors: WK
authors: Milsom
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001717:Birds / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D001833:Body Temperature Regulation / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D008116:Lizards / Q000502:physiology*; D008322:Mammals / Q000502:physiology; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D022722:Thermogenesis / Q000502:physiology*
keywords: Evolution; Life sciences; animal science; breeding season; endothermy; lizard; parental care; reptile; thermogenesis