Many freshwater turtles are extremely tolerant to the lack of oxygen and can survive the winter submerged in anoxic mud in ice-covered lakes. The pronounced anoxia-tolerance resides with a considerable depression of cellular metabolism and the ability to use the shell to buffer the acidosis arising from anaerobic metabolism (1). Infusion of microspheres has shown that the shell receives almost half of the cardiac output in turtles made anoxic at low temperatures (2). However, the vasculature of the turtle shell remains to be described. To visualise the vasculature within the carapace and plastron of the turtle Trachemys scripta, we perfused terminally anaesthetised turtles with different contrast enhancing agents (Microfil [lead n/a]), barium sulphate [250 mg/kg], and iodine [15-250 mg/kg]), and the animals were then scanned by both single source as well as dual energy Computed Tomographic systems, to create three dimensional representations. Dual energy Computed Tomography provided good visual contrast between blood vessels and bony tissue inside the turtle shell due to differences in energy level from the two simultaneously acquired x-ray sources. However, inadequate resolution of the clinical scanners prevented visualisation of the smaller vessels with a diameter below approximately 600 μm. Thus, our technique clearly revealed the larger intracortical vessel embedded in the carapace and plastron of Trachemys, and future studies should seek to determine whether this vascularisation is altered during prolonged anoxia. 1. Jackson, DC. (2011). Life in a shell: a physiologist´s view of a turtle. Harvard University Press, USA. 2. Stecyk, JAW., Overgaard, J., Farrell, AP., Wang, T. (2004). α-Adrenergic regulation of systemic peripheral resistance and blood flow distribution in the turtle Trachemys scripta during anoxia submergence at 5˚C and 21˚C. J. Exp. Biol. 207, 269-283.
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Society for Experimental Biology, SEB Annual Meeting 2011