Temperature acclimation in the pancake tortoise, Malacochersus tornieri: Metabolic rate, blood pH, oxygen affinity and red cell organic phosphates

Abstract

1. The effect of temperature acclimation (20 and 35°C) on blood gases, pH and the oxyhemoglobin dissociation curve was studied in the pancake tortoise. 2. 2. Cold-acclimated tortoises had blood with a lower O2 affinity (Fig. la) and lower Bohr effect (Fig. 1b) than warm-acclimated tortoises. 3. 3. The concentration of ATP in red cells was significantly higher in cold-acclimated tortoises, providing a mechanism for the temperature-induced affinity change of whole blood (Table 1; Fig. la and b). 4. 4. The cofactor-free hemoglobins from warm- and cold-acclimated tortoises showed no significant differences in oxygen-binding properties or in charge heterogeneity (Figs. 3 and 4). 5. 5. Two major hemoglobin components isolated show slight differences in oxygen affinities but both are sensitive to ATP (Fig. 5). 6. 6. The effect of temperature on blood pH, PCO2, HCO/t-3 and ventilation/O2 uptake was similar to that reported for turtles (Jackson, 1971; Jackson et al, 1974). 7. 7. Cold-acclimated tortoises had a significantly higher O2 uptake at 20°C and a lower Q10 than warm-acclimated tortoises (Fig. 2). 8. 8. The lower O2 affinity of blood after cold acclimation may be adaptive to the increased requirement for oxygen delivery to the tissues.