Oxygen storage capacity and tolerance of submergence of a non-aquatic reptile and an aquatic reptile

1. 1. The oxygen storage capacities and the tolerance to submergence of an aquatic snake, Natrix sipedon, and a non-aquatic snake, Crotalus viridis, were determined and compared. 2. 2. C. viridis was found to have a larger oxygen storage capacity, hemoglobin content and blood volume than N. sipedon. 3. 3. The submergence time for C. viridis was 30.13 min which was less than the estimated time for submergence based on the oxygen storage capacity. 4. 4. N. sipedon exceeded its estimated dive time of 24.00 min and remained submerged for 65.57 min without signs of stress. 5. 5. During submergence, the heart rate of N. sipedon fell to 9% (5 beats/min) of the resting rate, while the heart rate of C. viridis fell to only 75% (27 beats/min) of the resting rate during this activity. 6. 6. These data indicate that N. sipedon responds to submergence via a typical diving reflex and extends its oxygen stores beyond that expected of a non-diver such as C. viridis.