RESPIRATORY RESPONSES TO LONG-TERM TEMPERATURE EXPOSURE IN THE BOX TURTLE, TERRAPENE-ORNATA

In late February, seven box turtles were collected with body temperatures between 7 and 9°C. Ventilation, gas exchange and end-tidal {Mathematical expression} and {Mathematical expression} were recorded at 5, 10, 15 and 25°C, the animals being at each temperature for 2 to 3 weeks. There was a pronounced diurnal rhythm of breathing frequency at all temperatures. At 5°C the mean 24-h frequency was only 3.7 breaths h-1. At 15°C the frequency was 16 times higher with a 17-fold increase of ventilation. Oxygen uptake only changed from 3.4 to 12.7 ml·kg-1·h-1. Consequently, the ratio (ventilation, ml BTPS/O2 uptake, ml STPD) increased from 12.5 at 5°C to 48 at 15°C, but decreased to 24 at 25°C. The decrease of this ratio during cold exposure contrasts with an increase of the ratio during cooling earlier reported for fresh water turtles, Pseudemys. Cutaneous CO2 elimination was important at low temperature. This caused a decrease of the pulmonary gas exchange ratio so that end-tidal {Mathematical expression} remained low at 5°C in spite of an end-tidal {Mathematical expression} of only 54 Torr. © 1979 Springer-Verlag.