Biology ETDs


Casey Gilman

Publication Date



During gravidity lizards experience a significant decrease in lung volume as a result of compression by growing eggs within the body cavity. In order to understand the effect of this decrease in lung volume on respiratory physiology of gravid egg-laying lizards I measured changes in: total lung volume, resting and post-exercise expired volume, minute volume, respiratory frequency, and carbon dioxide production during reproduction in Crotaphytus collaris and Gambelia wislizenii. I found that compression of the lungs by eggs resulted in an average 48% (range: 26 to 70%) decrease in total lung volume in C. collaris, and an average 38% (range: 29 to 46%) decrease in G. wislizenii. Despite the significant reduction in lung volume in both of these species, only breathing frequency and rate of CO2 production were significantly altered. Breathing frequency was greatest in both species when females were carrying shelled eggs, and CO2 production rate was greatest in females of C. collaris when they were carrying late-stage follicles. The significant increases in breathing frequency in both species were large enough to compensate for the decrease in lung volume and maintain relatively constant minute ventilation in both species. Crotaphytus collaris and G. wislizenii appear to be able to withstand large changes in lung volume during reproduction with little respiratory compensation.

Project Sponsors

National Science Foundation Long Term Ecological Research Program; Sevilleta National Wildlife Refuge; American Society of Ichthyologists and Herpetologists; Graduate and Professional Student Association, UNM; Biology Graduate Student Association, UNM; Department of Biology, UNM; W.M. Keck Foundation; New Mexico Center for Isotopes in Medicine; UNM College of Pharmacy; University of New Mexico Cancer Center; University of New Mexico Health Sciences Center.




lizard, ventilation

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Toolson, Eric

Second Committee Member

Brown, James