THERMAL-ACCLIMATION OF AEROBIC METABOLISM AND O-2-HB BINDING IN THE SNAKE, VIPERA-BERUS

Snakes, Vipera berus, were acclimated to 5 and 25 °C for 3 months preceding measurements of O2 uptake and blood respiratory properties. O2 uptake measured at the lower acclimation temperature (5 °C) shows lower values for the cold-acclimated snakes. Measured at 25 °C cold-acclimation results in O2 uptakes slightly higher than in warm-acclimated snakes. The temperature sensitivity (Q10) of aerobic metabolism in thus higher for the cold-acclimated snakes being 3.17 compared to 2.11 for the warmacclimated. O2-Hb dissociation curves of whole blood from the two acclimation groups show a marked increase in O2 affinity associated with cold-acclimation independent of blood pH. The shift in O2 affinity correlates with a marked decrease in red cell organic phosphate concentration (ATP) in cold-acclimated snakes. The temperature sensitivity of the O2-Hb binding expressed by the ΔH values was rather uniform at about -11 kcal·mol-1 (O2) for both acclimation groups. The CO2 Bohr factor in cold-acclimated blood at -0.55 was about double that in warm-acclimated. The n value for both acclimation groups increased with higher temperatures. Hematocrit and blood O2 capacity were higher in the cold-acclimated snakes. The acclimation effects on O2 uptake, O2-Hb affinity and the Bohr effect, are opposite to those obtained earlier on reptiles at lower latitudes. It is discussed how a downward translation of the O2 uptake-temperature curve and a high thermal sensitivity (Q10) may be adaptive for species at latitudinal extremes where the active season is short and diurnal temperatures fluctuate widely. It is further discussed how a change in O2 affinity by its influence on the capillary to cellular O2 gradients may affect the aerobic metabolism. © 1979 Springer-Verlag.