Effects of temperature transients on gas exchange and acid-base status of turtles

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Abstract
Pulmonary ventilation (.ovrhdot.VE), O2 consumption (.ovrhdot.VO2), and CO2 production (.ovrhdot.VCO2) were measured continuously on each of 10 turtles, Pseudemys scripta elegans, at 20.degree. C, during and for 1 h after heating to 30.degree. C and during and for 1 h after cooling to 20.degree. C. In 7 of the animals, arterial blood was sampled at the 3 temperature plateaus. Ventilatory ratios (.ovrhdot.VE/.ovrhdot.VO2 and .ovrhdot.VE/.ovrhdot.VCO2) and metabolic rate adjusted promptly to temperature change, stabilizing at values similar to those observed previously in turtles following 1 day or more at each temperature. Likewise, mean blood pH and PCO2 values conformed both in absolute values and in temperature-dependence to data previously obtained from animals exposed to the various temperatures for longer time periods or from turtle blood thermally equilibrated in vitro. Total plasma [CO2] did not change significantly, suggesting that steady-state CO2 exchange prevailed throughout the experiment. In accordance with this, R(.ovrhdot.VCO2/.ovrhdot.VO2) did not change significantly during the 20-30.degree. C transition; R rose during the 30-20.degree. C transition, suggesting possible hyperventilation at this stage. The respiratory control of blood acid-base status adjusts rapidly to temperature change in the turtle and its adjustment minimizes disturbance to CO2 balance.

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