Cardiorespiratory effects of temperature in the turtle, Pseudemys floridana

Weight specific VO2 of resting Pseudemys floridana at body temperatures (BT) between 12 to 38 C was studied in relationship to VE, VT, f, pulmonary and systemic blood flow, and blood PO2, PCO2, pH and O2 content. The slope of the curve for VO2 against body mass was similar to that for mammals and differed from that of lizards. VE increased with BT while VE/VO2 fell, resulting in an elevation of arterial PCO2 and a decline in arterial pH of 0.013 unit/degrees C [HCO-3] and total CO2 remained constant. Increments in VE were achieved by decreasing apneic time and increasing VT up to VT of 18 ml.kg-1 when further rise in VE was exclusively on account of breathing frequency. Mean pulmonary and arterial blood flows were incremented in direct proportion to VO2, and no net intracardiac shunts was demonstrable. Ventilation-perfusion ratio fell with BT while EO2 increased. Arterial hemoglobin saturation varied inversely with BT while the arteriovenous O2 difference remained constant. EO2 was found to be highly dependent on the constant blood convection requirement as VE/VO2 fell. At similar BT, VE/VO2 was similar to that for man while Qpul/VO2 was in inverse proportion to maximum O2 capacity of the blood for the two species.