All ETDs from UAB

Advisory Committee Chair

Thane Wibbels

Advisory Committee Members

Ken Marion

Larry Boots

Document Type


Date of Award


Degree Name by School

Master of Science (MS) College of Arts and Sciences


A variety of reptiles have temperature-dependent sex determination (TSD), where incubation temperature determines gender. This form of sex determination has significant conservational implications because it has the potential of producing highly biased sex ratios which can affect the reproductive output of a population. TSD is of particular interest to conservation programs that use hatcheries to artificially incubate the eggs of endangered sea turtles because such programs need to select specific incubation temperatures in an effort to produce a desired sex ratio. This type of sex determination also has evolutionary implications as it may be advantageous for an animal to produce a specific gender under certain circumstances. The theory of differential fitness in regard to TSD implies that certain incubation temperatures may produce individuals of a particular sex due to a fitness advantage. However, actual physiological mechanisms behind this have received little or no attention. To address the evolutionary and conservational implications of TSD, this study evaluated the effect of specific incubation temperatures on the morphology and endocrinology of the gonads and reproductive tracts in a turtle with TSD. Through comparison, many significant differences were found that could be a potential mechanism iii for differential fitness in these reptiles and could provide insight into which incubation temperatures are optimal for artificial hatchery programs. This study also estimated the hatchling, immature, and adult sex ratios of leatherback sea turtles from nesting beaches on the Atlantic coast of Florida (through nest temperature analysis) and from in-water capture off the coast of Nova Scotia (through blood plasma radioimmunoassay). Estimated sex ratios were found to be primarily female biased. This information can provide guidance for conservation programs with this species. Collectively, the results provide insight into two key topics concerning TSD. First, the natural sex ratio data are a prerequisite for understanding the ecology of endangered sea turtles and for developing conservation strategies for their recovery. Secondly, the incubation results provide a possible link between temperature and reproductive fitness, thus providing a potential mechanism for the evolutionary advantage of TSD. Both findings have significant implications for the conservation, ecology, and evolution of reptiles with TSD.



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