Blood physiology and oxygen transport during activity in two lizards, Varanus gouldii and Sauromalus hispidus.

l. Aspects of blood physiology-hematocrit, oxygen capacity and affinity, lactate content, pH and composition of blood buffers-were investigated in the lizards Varanus got&z% and Sauromalus hispidus during activity at different temperatures. 2. Although oxygen capacity and affinity, resting pH and lactate levels, bicarbonate and phosphate concentrations are nearly identical in both species, only Sauromalus sustains a decrease in blood pH during activity, accompanied by a decrease in oxygen capacity and afhnity, high levels of lactate production and exhaustion. 3. Non-carbonic blood buffers prevent a change in blood pH in Vurunus. Lungs of great surface area facilitate exchange of oxygen and carbon dioxide, and Varanus undergoes only moderate lactate generation and remains aerobic during activity.