Oxygen Consumption, Ventilation, and Oxygen Pulse of the American Alligator during Heating and Cooling

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Abstract
Respiratory measurements of 9 American alligators, Alligator mississippiensis (1.5-8.78 kg, mean 3.80), during heating and cooling are reported. The animals were cooled to 15.degree. C for 24 h, then transferred to a 35.degree. C chamber with an air flow of 300 cm/s. After equilibration at 35.degree. C the animals were transferred back to the 15.degree. C chamber and cooling measurements obtained. All animals heated faster than they cooled. O2 consumption (VO2), heart rate, respiration rate and expired volume (VE) were measured under dynamic conditions. Apparently these are the 1st measurements reported for crocodilians. Related measurements in the literature were made under static conditions, and the responses to changing temperature were not measured. Mean values at the mid-temperature (25.degree. C) during warming and cooling, respectively, were: heart rate (beats/min) 29.3, 23.1; ventilatory rate (breaths/min) 1.5, 3.3; VE (ml/kg per min) 22.3, 60.1; VO2 (ml O2/g per h) 0.033, 0.105; VE/VO2 43.6, 29.2 O2 pulse (.times. 10-6 ml O2/g per heart beat) 17.6, 75.0; and respiratory quotient (RQ) 0.69, 0.88. ventilatory rate VO2, VE, O2 pulse, and RQ generally increased at higher temperatures and cooling values exceeded warming values for any given body temperature (TB). O2 consumption may be related to TB (under static conditions) and body weight (W) in grams as: ml O2/g per h = 0.0673 W-.31 (TB-12.67.degree. C). Heart rate and the ratio VE/VO2 during warming exceeded cooling values at the same TB. The ratio VE/VO2 decreased with increasing temperature, especially during warming. Heart rate increased with temperature. The alligator demonstrated profound physiological responses to heating and cooling, indicating the importance of defining the recent thermal history of experimental animals.