ELF, P.*; LANG, J.; FIVIZZANI, A.; University of Minnesota Crookston; University of North Dakota, Grand Forks: Relationship between Yolk Hormone Levels and Female Size in two TSD Turtles

Yolk steroid hormones have been reported to impact development, growth and behavior in avian species. While these interactions have not yet been investigated in oviparous reptiles, we have implicated yolk steroid hormones in the sex determination process in reptiles with temperature-dependent sex determination (TSD). We have reported initial hormone levels and their changes during embryonic development for some TSD species, but the factors responsible for establishing the variation in yolk hormone levels among individual females have yet to be determined. In order to elucidate any relationship between female size/age and yolk steroid hormones, we analyzed initial hormone levels in conjunction with other clutch characteristics of eggs collected from two TSD species, Chelydra serpentina (snapping turtles) and Chrysemys picta (painted turtles). We found no correlation between yolk estradiol (E₂) or testosterone (T) and female weight in painted turtles (for E₂, P=0.6873 and 0.5653; for T, P=0.8181 and 0.6663 for pre- and post lay weights, respectively) or total clutch mass (for E₂, P=0.3315 and P=0.4902; for T, P=0.5595 and P=0.1589 for Chelydra and Chrysemys, respectively) in either turtle. Further, there were no correlations between yolk E₂ or T and individual egg mass (for E₂, P=0.7851 and 0.1276; for T, P=0.9728 and 0.2059 for Chelydra and Chrysemys, respectively) or total egg number (for E₂, P=0.9456 and 0.3684; for T, P=0.7521 and 0.1172 for Chelydra and Chrysemys, respectively) in either species. This would indicate that environmental and/or inherited factors may be responsible for establishing individual female yolk hormone levels in these TSD turtles.