ALLMAN, Phil; PLACE, Al; ROOSENBURG, Willem; Ohio University, Athens, OH 45701; Center of Marine Biotechnology, University of Maryland, Baltimore, MD 21202; Ohio University, Athens, OH 45701: Sex differentiation in three populations of Malaclemys: a turtle with temperature-dependent sex determination

Sexual differentiation in reptiles with temperature-dependent sex determination (TSD) is known to be influenced by several factors including nest site choice and maternally derived hormones. Collectively these influences may play an adaptive role for the maintenance of TSD. In wide ranging species, these influences may be important for adjusting the dynamics of TSD to better match local environmental conditions. With a range from Massachusetts to Texas, the diamondback terrapin is a wide ranging emydid turtle that shows geographic variation in reproductive strategy. Northern populations exhibit a shorter nesting season and deposit fewer clutches characterized by a larger number of smaller eggs. More southern populations have a longer nesting season where more clutches of larger, but fewer, eggs are laid. To analyze the potential variation in developmental characters associated with TSD, eggs were collected from three terrapin populations and incubated at 29.5�C. There was no difference in the sex ratios produced from clutches collected from the three locations. Female gonads one month after hatching had higher aromatase activity than males, but brain tissues showed no sex-specific aromatase differences. Aromatase activity in the gonad at nine months of age was lower than at one month, but maintained sex specific activity. Aromatase activity in the brain at nine months was much higher than at one month and continued to show no sex-specific patterns. Hatchlings from New York grew at a slower rate than hatchlings from Maryland and Florida. Furthermore, hatchling lipid analysis indicated a higher proportion of non-polar lipids in the FL population than in both northern populations.