WOODS, H.A.; Univ. of Texas, Austin: Causes and consequences of temperature-oxygen interactions in metabolism

Biochemical reaction rates change more with temperature than do physical rates such as diffusion. Consequently, organisms exposed to rapid or high-magnitude temperature variation may experience profound variation in relative oxygen supply and demand. This problem is faced by all ectotherms that depend on oxygen diffusion�which includes a larger range of taxa than is often appreciated. I will illustrate this issue with recent work from my lab on terrestrial insect eggs and marine opisthobranch egg masses. Insect eggs and marine egg masses are obviously different, in size, physiology, and habitat. Yet, for both, high temperature gives internal oxygen pressures low enough to limit rates of metabolism and development. Together with other similar data from the literature, my results suggest that temperature-oxygen interactions are pervasive, constituting a fundamental physiological reality for most organisms. This observation suggests several broad questions, which I will touch on briefly: What common constraints emerge from temperature-oxygen interactions? What means do different taxa use to mitigate constraints? Are there fundamental differences in how terrestrial and marine systems deal with oxygen deprivation? And how does differential temperature sensitivity affect the evolution of metabolic systems?