Wyneken, J.*; Steinberg, F.: The Use of CT and Functional MRI to Examine Cardiopulmonary Structure and Function in Ecologically Distinct Species of Turtles.

Sea turtles are secondarily aquatic are migratory specialists. As such, they possess suites of morphological, behavioral and physiological adaptations for migratory life. These include unique sets of cardiopulmonary structures that may serve as adaptations for prolonged submergence while active. Through the use of Computed Tomography (CT) to map the extent of the lung and structural and functional Magnetic Resonance Imaging (MRI and fMRI) the function of the cardiopulmonary system can be observed in unanesthetized animals in a noninvasive manner. The CT and fMRI images, plus dissections of fresh material, suggest the following. (i) The ventricles of sea turtle functionally separate systemic and pulmonary flow. (ii) The pulmonary arteries intermittently profuse the lung while venous flow is more constant. (iii) When shunting from the pulmonary to systemic systems occurs, several sites are involved (the ventricular chambers, from the pulmonary circuit to the systemic circuit via selective constriction of the pulmonary arteries and at locations between the pulmonary arteries and veins) suggesting control of perfusion at several levels. Comparisons were extended to one species of nonmarine turtle (Trachemys), a less migratory and very shallow diving species. Observations to date reveal the presence of no pulmonary shunts, a result that supports the hypothesis that pulmonary shunting is dervived adaptation found in deep-diving and/or highly migratory aquatic turtles.