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Matthew E. Wilson1 *, Fredric J. Janzen II1 , Stephen P. Ford.1 *
Iowa State University, Ames, IA 1
It is believed that steroids play a key role in temperature dependent sex determination, mediating the effect of temperature on gonadal development. Trachemys scripta elegans females deposit significant amounts of testosterone (T4) into the yolk of their eggs. This opens the possibility that compounds like phytoestrogens and steroid-like pollutants injested or absorbed by females could end up in the yolk, impacting embryonic development. It is not surprising that turtles would deposit T4, as it can serve as a substrate for aromatization to estradiol-17 (E2) or reduction to dihydrotestosterone (DHT). To further investigate the role of yolk steroids on turtle development we wanted to establish a method for modulating yolk steroid concentration, by elevating systemic levels in the female. This was accomplished by subcutaneous placement of implants containing no steroid, or 2.5 mg of T4, E2 or DHT into T. s. elegans females (8/group) at the start of September and again 4 weeks later. We sampled blood from the brachial sinus immediately prior to implantation and every 2 weeks until hibernation, which began in November. Females were then maintained at 6°C, brought out of hibernation in April and again blood sampled. Prior to hibernation circulating levels of steroids increased markedly (P<.05) for each group (100 fold for T4, 4 fold for DHT and 8 fold for E2) when compared to preimplantation values. By Spring, values had returned to baseline for all 3 steroid treated groups. A subset of control (n=5) and T4 (n=4) turtles were sacrificed in May to collect mature follicles. T4 concentrations were greater (P<.05) in yolk from T4-treated females compared to those from controls (215±28 vs 37±8 pg/mg). These data demonstrate the potential of using subcutaneous implants impregnated with steroids as a method for manipulating yolk steroid concentrations.
This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.