Effect of temperature on the heart in the alligator

¹ Marine Biological Laboratory, Woods Hole, Massachusetts

Electrocardiograms were taken on 12 alligators, 18–30 inches in length. Some were exposed to elevated temperatures; the resulting ECG's were compared with controls obtained at 22°C, which were as follows: rate, 40/min.; P-R, 0.4 seconds; Q-T, 0.6 seconds; T, 0.24 second, 0.05 mv; QRS, 0.04 second. Heart rate increased with increased colonic temperature. At 34°C there was marked increase in variability of rate. Above 40°C the heart became irregular and was damaged irreversibly. Duration of T decreased with elevated temperature to about 33°C above which T was prolonged. Optimal temperature for the alligator in terms of tolerance and general behavior is between 32°C and 35°C, with a critical maximum of 38°C. Slightly above that temperature the heart became disorganized. The present results suggest that the alligator's temperature preferendum is sound with respect to cardiac well being.