Research
Current Research Projects
1. I am currently working with softshell turtles (Apalone spinifera); looking at their capacity to extract oxygen from aquatic habitats under different conditions. This project is mostly a lab based project, but some field work is involved to gather the animals; I have some specimens to work with, but I'm always on the hunt for new individuals.
2. In addition, I am working on project with the local slider turtle (Trachemys scripta); looking at the development of bone in hatchling turtles. This project has 2 components to it, a field component tracking turtle nests in natural conditions to determine when the hatchling in this area emerge from the nest and enter the water. It also has a laboratory component where we bring hatchling turtles into the lab and raise them up, sampling their bone growth periodically to determine when bone first starts to develop and how long it takes for juvenile bone to complete development into adult bone.
3. Finally, I have a project looking at the physiological mechanisms that allow some species of fishes to inhabit urbanized streams while others cannot. Currently, we are working with Campostoma oligolepis as our model organism for a moderately tolerant animal. Eventually, this work will expand to include other fishes that span the spectrum from extreme tolerance of urbanized watersheds to no tolerance for urbanized watersheds.
If you have an interest in any of these projects and would like to do some research with me, please don't hesitate to contact me. I work with interested students whether they really need credits or not.
Comparative Physiology of Hibernation in Reptiles and Amphibians
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 anddifferences 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.
Recent Publications
Reese S. A., G. R. Ultsch, and D. C. Jackson. 2004. Lactate accumulation, glycogen depletion, and shell composition of hatchling turtles during simuilated aquatic hibernation. Journal of Experimental Biology. 207:2889-2895.
Reese S. A. , D. C. Jackson, and G. R Ultsch. 2002. The physiology of overwintering in a turtle that occupies multiple habitats, the common snapping turtle ( Chelydra serpentina ). Physiological and Biochemical Zoology . 75(5): 432-438.
Reese S. A. , D. C. Jackson, and G. R Ultsch. 2003. Hibernation in freshwater turtles: softshell turtles ( Apalone spinifera ) are the most intolerant of anoxia among northern species. Journal of Comparative Physiology B 173: 263-268.
