Term of Award

Fall 2010

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

David C. Rostal

Committee Member 1

Lance D. McBrayer

Committee Member 2

J. Scott Harrison

Committee Member 3

n/a

Abstract

The yellow-bellied slider (Trachemys scripta scripta) is one of the most common species of freshwater turtles in the southeastern United States, yet little information pertaining to its reproductive biology and seasonal hormone cycle has been documented. The major purposes of this study were to: (1) compare the use of ultrasound, x-ray, and oxytocin in determining reproductive status of females not collected at the nesting site and (2) identify the effects of water temperature on the seasonal testosterone cycle of males and females from two populations influenced by different water temperature regimes. Ultrasound was useful in determining presence and size of vitellogenic and atretic follicles throughout the sample period as well as oviductal eggs during the nesting season. X-ray was able to detect eggs at different levels of calcification throughout the nesting season and was useful for measuring overall egg length, width, and clutch size. Oxytocin was 95% successful in producing at least one egg, but success rates for full clutches were not as high for this study as in other studies. Water temperature at Magnolia Springs State Park (MS) was consistently warmer than at George L. Smith State Park (GLS) during winter months. Male T. s. scripta exhibited a post-nuptial increase in testosterone during the fall months and peaks occurred in September at both sites. Females exhibited a nuptial peak in testosterone which correlated with timing of mating and ovulation but occurred in different months (MS: March, GLS: May). Temperature appears to have a major impact on timing of reproductive events in this species and may have a greater effect on females than males. By combining the use of ultrasound, x-ray, and oxytocin with analysis of circulating plasma hormone concentrations, researchers can gain a better understanding of the interactions between biotic and abiotic factors influencing reproduction.

Share

COinS