My research looks at the evolutionary paths that have led to physiological mechanisms allowing amphibians and reptiles
to survive during the harsh winter environments found in the northern United States. I use a comparative approach, looking at respiratory and acid-base physiology among several species that utilize different mechanisms for surviving during winter months. Comparing similarities and differences amongs species allows us to map physiological evolution and helps to identify evolutionary mechanims that may have influenced the development of certain physiological traits.
The main body of my work has focused on aquatic turtles. In the northern portions of their ranges, aquatic turtles escape freezing temperatures spending the winters submerged underwater. This presents the air-breathing turtle with a suite of physiological challenges; one of the most prominent being a severe reduction in the availability of oxygen. To make matters more difficult, some species of turtles (e.g. Painted turtles, Chrysemys picta) spend considerable portions of their winter submergence in the mud where oxygen is near zero year round. In my research, we have compared the mechanisms that allow painted turtles to survive these winter soujorns to physiological mechanisms in other turtles (e.g. map turtles, Graptemys geographic; softshell turtles, Apalone spinifer; musk turtles, Sternotherus odoratus; and snapping turtles, Chelydra
serpentina) that must also survive these northern winters. We have identified differing abilities for dealing with low oxygen conditions, however mechanisms involved are surprisingly similar.
In looking at hibernation physiology, I have utilized surgical techniques for blood sampling to measure respiratory, acid-base and ionic variables during the animals winter submergences. In addition, I have been using analytical chemical techniques to look at bone composition and buffer release. I have also established collaborations with Brown University's Department of Orthopaedics for looking at the mechanical strength of turtle bone under various winter conditions. I have looked at other respiratory processes involved in overwintering including the use of extr- pulmonary respiratory mechanisms in the exchange of carbon dioxide and oxygen.
