Embryonic sex steroid hormones accumulate in the eggshell of loggerhead sea turtle (Caretta caretta).

Abstract Steroids hormonessuch as estradiol-17β (E2) and testosterone (T) are involved in gonadal differentiation of oviparousanimals with temperature-dependent sex determination(TSD), and are greatly distributed. This hypothesizes that these embryonic steroid hormonesprobably accumulate in the eggshellthroughout blood or/and chorioallantoic fluid in sea turtlespecies with TSD, producing females at higher temperature. To demonstrate this hypothesis, concentrations of E2 and T in the blood plasmafrom the hatchling loggerhead sea turtle( Caretta caretta ) and in their eggshellswere measured by radioimmunoassay. In the present study we propose that both concentrations of E2 and T in the blood plasmaare correlated with amounts of these sex steroidsin the eggshell. Moreover, contents of E2 in the eggshellshowed a significant positive correlation with mean incubation temperatures during a thermosensitive period in the experimental nests, whereas T contents in the eggshelldid not. Taken together, these findings indicated that embryonic E2 and T that accumulated in the eggshellcan be extracted and measured. Furthermore, the present study suggested that contents of E2 in the eggshellmay differ between male and female, and monitoring of these steroids is a useful method to identify the sex of loggerhead sea turtle hatchling.