Thermal Dependence of Air Convection Requirement and Blood Gases in the SnakeColuber constrictor

Abstract

In this report I discuss ventilatory and circulatory adjustments that prov for increased O2transport associated with increased body temperature in the snake Coluber constrictor . Also included is the effect of temperature upon acid-base status. Minute ventilation increases with rising body temperature but does not keep pace with the increment in resting O2 consumption. The decrease in air convection requirement ( i.e. , ventilation ÷ oxygen consumption) causes lung pO2 and arterial oxygen contentto fall and lung pCO2 to rise. With the rise in lung pCO2, systemic arterial pCO2 and H+; concentration increase while plasma bicarbonate concentration does not change. The effect of temperature upon air convection requirement, arterial pCO2, and pH are most pronounced at body temperatures above about 27°C where Coluber behaves approximately as an alphastat pH regulator. Despite the inverse relationship between temperature and lung pO2, systemic arterial pO2 is about 80 torr lower at 15°C than at 35°C. This decline in arterial pO2 as temperature falls is explained by left shifting the oxygen dissociation curve in the presence of aconstant right-to-left intracardiac shunt.