Incubation temperature influences sex-steroid levels in juvenile red-eared slider turtles, Trachemys scripta, a species with temperature-dependent sex determination.

Incubation temperature determines gonadal sex in the red-eared slider turtle, Trachemys scripta. However, little is known about the long-term effects of incubation temperature on traits other than gonadal sex in this species. To investigate the hypothesis that incubation temperature (independent of gonadal sex) influences sex steroid levels after hatching, we incubated eggs of the red-eared slider turtle at three temperatures (26, 28.6, and 31 degrees C). We then measured plasma levels of dihydrotestosterone, estradiol, progesterone, and testosterone in 6-wk-old males from 26 degrees C and 28.6 degrees C eggs, and in 6-wk-old females from 28.6 degrees C and 31 degrees C eggs. We found that dihydrotestosterone levels were not influenced by incubation temperature or gonadal sex. However, progesterone levels were significantly higher in males from 26 degrees C eggs than in males from 28.6 degrees C eggs. In contrast, testosterone levels did not differ between males from 26 degrees C versus males from 28.6 degrees C eggs, but they were significantly higher in females from 28.6 degrees C than in females from 31 degrees C eggs. Progesterone and testosterone levels did not differ between males and females from 28.6 degrees C eggs. Temperature also influenced estradiol levels in both sexes, but the effects were enigmatic. We conclude that incubation temperature has lasting effects on sex steroid levels even after hatching.