Oxygen supply limits the heat tolerance of lizard embryos.
The mechanisms that set the thermal limits to life remain uncertain. Classically, researchers thought that heating kills by disrupting the structures of proteins or membranes, but an alternative hypothesis focuses on the demand for oxygen relative to its supply. We evaluated this alternative hypothesis by comparing the lethal temperature for lizard embryos developing at oxygen concentrations of 10-30%. Embryos exposed to normoxia and hyperoxia survived to higher temperatures than those exposed to hypoxia, suggesting that oxygen limitation sets the thermal maximum. As all animals pass through an embryonic stage where respiratory and cardiovascular systems must develop, oxygen limitation may limit the thermal niches of terrestrial animals as well as aquatic ones.
School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA.
Colton
C
Smith
Department of Biology, University of Washington, Seattle, WA 98195, USA telemeco@uw.edu.
Rory S
RS
Telemeco
School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA.
Michael J
MJ
Angilletta
Department of Physiology, Midwestern University, Glendale, AZ 85308, USA.
John M
JM
VandenBrooks
D000064:Acclimatization / Q000502:physiology; D000818:Animals; D004625:Embryo, Nonmammalian / Q000502:physiology*; D006358:Hot Temperature / Q000009:adverse effects*; D008116:Lizards / Q000196:embryology / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption
D010100:Oxygen
Sceloporus tristichus; critical thermal maximum; oxygen-limited thermal tolerance; temperature