CROSSLEY, D. A.*; HICKS, J. W.; BENNETT, A.F.: Postprandial changes in cardio-respiratory responses of the Savannah monitor (Varanus exanthematicus

Cardio-respiratory control has been well characterized in numerous endothermic vertebrates, however our understanding of these systems in ectothermic vertebrates remains poorly understood. The purpose of this study was to thoroughly assess the cardiovascular and pulmonary responses to changes in ambient gas composition in the Savannah monitor, Varanus exanthematicus, in a fasted and fed state. Fasted animals exposed to graded hypoxia exhibited a ventilatory response characterized by an increase in Ve, Vt, fB. These changes were accompanied by a fall in arterial PO2 and PCO2 while arterial pH rose. In addition, hypoxia resulted in a progressive tachycardia but blood pressure remained constant. Graded hypercapnia produced an increase in both arterial PO2 and PCO2 while pH fell during each exposure. These changes were coupled with an elevation in all ventilatory parameters; however, cardiovascular parameters remained constant. 24 h after ingesting a standardized meal, baseline values of all measured parameters rose with the exception of arterial pressure and pH, which remained unchanged. Postprandial exposures to both the hypoxic and hypercapnic r�gime produced responses in all measured parameters that were similar to that of the fasted animal. Thus it appears that the control mechanisms are unaffected by feeding in the Savannah monitor.