The contribution of pulmonary‐to‐systemic cardiac shunting to growth, metabolism, and recovery from exercise in Alligator mississipiensis

Abstract

All non-avian reptiles have the capacity to mix oxygenated and deoxygenated blood (cardiac shunt), but the adaptive significance of cardiac shunting has not been tested. The fully divided ventricle of crocodilians allows for surgical elimination of the capacity for pulmonary-to-systemic (R-L) shunting by occluding the left aortic arch (LAo) outside of the heart. With the experimental removal of pulmonary-to-systemic shunt capacity we can make inferences about its physiological function in reptiles. We surgically tied off the left aortic arch (LAo) of hatchling American alligators (Alligator mississipiensis) both proximal and distal to the foramen of Panizza, thereby eliminating shunting. The alligators were divided into three groups: experimental (occluded LAo), sham-operated and non-operated control. We studied the consequences of the elimination of shunt capacity on SDA, resting metabolism, lactate clearance following exhaustive exercise and the growth parameters of body mass, head length, snout-vent length and total length. In the first nine months following surgery, growth shows a non-significant trend of decreased growth in experimental animals. Supported by NSF IOB grant #04445680 to JWH.