Physiological thermoregulation in turtles.

WEATHERS, WESLEY W., AND FRED N. WHITE. Physiological thermoregulafion in turtles. Am. J. Physiol. 22 l(3) : 704-7 10. 17 I. .The physiological capacity of turtles for altering rates of heat exchange was partially assessed by measuring rates of change of body temperature (Tb) during heating from 10 C to 30 C, and during cooling from 30 C to 10 C, in both air and water. In water, turtles heated an average of 2517~ faster than they cooled while in air the aquatic species studied exhibited rates of cooling which exceeded rates of heating. The latter observation was attributed to the influence of evaporative water loss. Heart rates showed a strong dependency upon respiration and no clear correlation of heart rate with differences between rates of heating or cooling could be demonstrated. Both cutaneous and carapace blood flows increased in response to heating and decreased in response to cooling (133Xe-clearance technique). These changes were independent of changes in heart rate or Tb . Peripheral vascular responses to heating and cooling appear to represent a means of changing functional insulation and may contribute to the thermoregulatory capacities of turtles under natural conditions.