Team DeNardo

Zach Stahlschmidt

Education:

B.S. with Honors. Animal Sciences. 2004. University of Illinois at Champaign-Urbana.

Research Interests:

My current research interests encompass the physiological, evolutionary, and ecological aspects of python brooding behavior.

Current Work:

My research investigates the python reproductive system using the Children's python (Antaresia childreni) as the primary model species. All female pythons exhibit a brooding behavior that involves tightly coiling around a clutch of eggs throughout an incubation period (more than 80 days in some species) characterized by self-imposed anorexia and dehydration. While other members of the DeNardo lab are studying the physiological and evolutionary significance of facultative endothermy exhibited by some python species during brooding, my research focuses on the implications of this parental care behavior independent of endothermy. Although this tightly coiled posture is likely designed to minimize water loss by the porous-shelled eggs, it may also reduce embryonic gas exchange (O2 and CO2). To address this dilemma, brooding females will occasionally open their posture to allow gas exchange, while minimizing egg dessication. This water conservation strategy has been proposed as a theory for the discontinuous gas exchange exhibited by some insects. Furthermore, one would also surmise that the postural changes of brooding pythons would increase in frequency and/or duration towards the end of the incubation period, as the developing embryos likely have much higher metabolic requirements at this stage. Given the very basic constructs of this system, my research questions include:

1. Do brooding pythons exhibit a discontinuous gas exchange mechanism?
2. How do embryonic metabolic requirements change throughout an incubation period?
3. Do extrinsic cues have any effect on python brooding behavior?
4. Do pythons in the wild behave similarly to captive-born pythons in the lab?

Do brooding pythons exhibit a discontinuous gas exchange mechanism?
Using a system that coupled open respirometry/hygrometry with an infrared camera, first year experiments tentatively indicate that slight postural adjustments correlate with short bursts of CO2 release, O2 consumption, and H2O loss. The early data also suggests that the duration between such minor postural adjustments dictates the amount of gas exchange (CO2 and O2) more so than the degree of egg exposure during each uncoiling event. Further analysis and future experiments may further elucidate the discontinuous gas exchange mechanism involved.

How do embryonic metabolic requirements change throughout an incubation period?
Using a closed respirometry system on single eggs from multiple python species, I determined that egg metabolic gas requirements increase 5-6 fold during incubation. Data from the open respirometry system confirms a similar trend among entire clutches. Hypothetically, this should drive increasing postural changes toward that latter portion of the incubation period.

Do extrinsic cues have any effect on python brooding behavior?
Future studies will address that possibility that brooding females use ecologically relevant cues from either the nest (via altering vapor pressure) or the clutch (via altering clutch temperature and/or CO2 production).

Do pythons in the wild behave similarly to captive-born pythons in the lab?
Future studies involving a field season in northern Australia and an innovative surgical procedure may allow for simultaneous thermal measurements of the nest, female, and clutch in a wild nesting environment. Overall, my research should clarify the physiological, evolutionary, and ecological role of python brooding behavior.

Past Research:

As an undergraduate at the University of Illinois, I conducted research under Dr. Lee Beverly that investigated neurophysiolgical mechanism involved in blood glucose regulation. I also assisted in post-baccalaureate research under Matthew Richardson and Dr. Jeffrey Brawn that encompassed land-use ecology of prairie kingsnakes, small mammals, and northern bobwhite quail in a grassland system.

Publications

Guedet, N., Z. Stahlschmidt, L. Arseneau, and J. Beverly. (2003) Effect of recurrent glucoprivation on interstitial glucose concentration in the ventromedial hypothalamus. FASEB Journal 17(5).

Acknowledgements

De Vries, M. et al. (2003) Extracellular glucose in rat ventromedial hypothalamus during acute and recurrent hypoglycemia. Diabetes 52.

De Vries, M., M. Lawson, and J. Beverly. (2005) Hypoglycemia-induced noradrenergic activation in the ventromedial hypothalamus is a result of decreased ambient glucose. American Journal of Physiology 289(4).

Doane, D. et al. (2005) Orexin A increases glutamate and decreases GABA release in the perifornical region of the lateral hypothalamus. (not yet published).

Richardson, M. (2005) Effects of prescribed burning on small mammals and snakes in midwestern grassland. Restoration Ecology (accepted).

Richardson, M. (2005) Activity patterns and habitat preferences of the prairie kingsnake (Lampropeltis calligaster calligaster) in Illinois. Herpetology (accepted).

Poster presentations

Guedet, N., Z. Stahlschmidt, L. Arseneau, and J. Beverly. Effect of Recurrent Glucoprivation on Interstitial Glucose Concentration in the VMH. Experimental Biology Conference, 2003.

Stahlschmidt, Z. Effect of unilateral injections of Orexin A on GABA and glutamate levels in the lateral hypothalamus. James Scholars Honors Conference, University of Illinois, 2004.

Email: zach_stahlschmidt@yahoo.com