INTERACTION BETWEEN TEMPERATURE AND HYPOXIA IN THE ALLIGATOR

Hypoxia elicits behavioral hypothermia in alligators. Under normoxic c onditions, the selected body temperature is 27.8 +/- 1.2-degrees-C. Ho wever, when inspired 02 is lowered to 4%, selected body temperature de creases to 15.4 +/- 1.0-degrees-C. The threshold for the behavioral hy pothermia is between 4 and 5% inspired 02, the lowest threshold measur ed so far in terrestrial vertebrates. This study assessed the physiolo gical significance of the behavioral hypothermia. The body temperature was clamped at 15, 25, and 35-degrees-C for measurements of ventilati on, blood gases, metabolic rate, plasma lactate, and acid-base status. Hypoxia-induced changes in ventilation, acid-base status, oxygen cons umption, and lactate were proportional to body temperature, being pron ounced at 35-degrees-C, less at 25-degrees-C, and absent at 15-degrees -C. The correlation between selected body temperature under severe hyp oxia and the measured parameters show that behavioral hypothermia is a beneficial response to hypoxia in alligators.