Term of Award

Fall 2015

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


Department of Biology

Committee Chair

David C. Rostal

Committee Member 1

D. Kelly McLain

Committee Member 2

J. Scott Harrison


Reproductive information, including seasonality in behavior and physiology, is key to our ability to breed species for maintaining assurance colonies or for future introductions. Limited scientific data is available about the reproduction of Helodermatid lizards. Several species of helodermatid lizard are uncommon, rare, or simply exist at low population densities and in need of the development of conservation programs and management. Most helodermatid reproductive data collected to date has been done on deceased animals using histological techniques. Until this study, no hormones have been analyzed, and individual animals have not been followed through a complete cycle. The purpose of this study was to delineate the reproductive cycle of the Guatemalan beaded lizard, Heloderma charlesbogerti, by monitoring seasonal steroid and calcium cycles, vitellogenesis, ovarian follicular growth, and egg production. Blood samples were collected monthly from adult captive lizards housed at Zoo Atlanta to determine circulating hormone levels. Testosterone and corticosterone levels in males and estradiol, corticosterone and calcium levels in females, were correlated with female reproductive condition determined by ultrasonography. Testosterone in male lizards peaked during August indicating that breeding should occur in September-October. Consistent with what has been observed in deceased wild specimens of Mexican beaded lizards (Heloderma horridum) with spermatogenesis in August through October. A distinct ovarian cycle was observed with small previtellogenic follicles appearing as early as November and vitellogenesis occurring from May to November. Ovulatory estradiol spikes were identified in some females in August and November. Corticosterone levels appear to increase in gravid females.

Included in

Endocrinology Commons