SECOR, S.M.*; WHITE, S.E.; University of Alabama, Tuscaloosa; Tidmore Veterinary Hospital, Northport, AL: Effects of exercise, digestion, and body mass on cardiac output and patterns of blood flow for the Burmese python (Python molurus)

In considering the tremendous metabolic response exhibited by pythons during meal digestion and the well-known phenomenon of blood shunting to active tissues, we measured heart rate, cardiac output (summed blood flow through the carotid arteries and dorsal aorta), and blood flow through the superior mesenteric artery and hepatic portal vein of Burmese pythons while fasting, exercising, and digesting. Pythons (0.5 � 14 kg) were surgically implanted with perivascular blood flow probes (Transonic Systems) and measurements were made of snakes at rest, crawling, during the digestion of rodent meal equaling in mass to 25% of snake body mass. Exercise generated a 2.5-fold increases in heart rate and cardiac output, while reducing blood flow to the small intestine by 65%. During the digestion of meals equaling 25% of body mass, pythons experienced respective 3, 4, 11, and 18-fold increases in heart rate, cardiac output, superior mesenteric arterial flow, and hepatic portal flow. In response to both exercise and digestion, heart rate and cardiac output do not change, whereas carotid blood flow more than doubles and blood flow through the superior mesenteric artery and hepatic portal vein is reduced by 85% and 55%, respectively. Whereas python heart mass scales (log-log) with body mass with a mass exponent of 0.76, cardiac output during rest, exercise, and digestion was found to scale with exponents between 0.61 and 0.66. Pythons in exhibiting the largest known postprandial increase in cardiac output and blood flow to the digestive system, demonstrate the impressive functional capacity of their cardiovascular system.