Meeting Abstract
Oxygen availability and temperature are two of the most important environmental factors affecting all of animal life. However, the two are not independent of each other and may exert similar selective pressures on animals. Life stages that have poorly developed circulatory systems or are incapable of oxygen regulation may be more susceptible to high temperatures at lower oxygen levels. Through a series of experiments on lizards, birds, and insects, we have begun to examine the interactive effect of oxygen and temperature on terrestrial animals exposed to hypoxia, high temperatures, and a combination of both during various life stages and levels of activity. While the results of these experiments have been mixed in their support for the concept of an effect of oxygen during periods of thermal stress, one pattern has emerged – the thermal tolerance of embryonic stages are particularly susceptible to oxygen variation. This pattern holds true for both ectotherms and endotherms. In embryonic lizards, hypoxia strongly reduced thermal tolerance, while hyperoxia mildly increased thermal tolerance. By contrast, quail embryos showed a marked decrease in thermal tolerance in hypoxia and a marked increase in thermal tolerance under hyperoxia indicating they are oxygen limited even under normal environmental conditions. However, while the embryos were significantly impacted by oxygen, the thermal tolerance of adult lizards and insects were unaffected by oxygen variation. Based on these experiments, the effect of oxygen on thermal tolerance varies depending on the life stage. More experiments under ecologically relevant conditions and behaviorally relevant activities need to be carried out to further test these hypotheses.
