Bowden Rachel M, Ewert Michael A, Nelson Craig E
Department of Biology, Indiana University, Bloomington 47405-3700, USA.
Gen Comp Endocrinol. 2002 Dec;129(3):171-7. doi: 10.1016/s0016-6480(02)00530-0.
This study investigates the potential effects of maternally derived hormones present in the yolk of reptile eggs. Specifically, we ask when are these hormones utilized by developing red-eared slider turtles (Trachemys scripta elegans), a species with temperature-dependent sex determination (TSD). Eggs were incubated at 27 degrees C, a male-producing temperature, and at 31 degrees C, a female-producing temperature. Concentrations of progesterone, testosterone, and 17beta-estradiol were measured at four points during development: at oviposition, at the start of the temperature sensitive period (TSP), at the end of the TSP, and at hatching. No effects of incubation temperature on yolk hormone concentrations were detected. The highest concentrations of all three hormones were measured at oviposition. Hormone-specific patterns of decline occurred throughout development. Each hormone declined between oviposition and the early TSP. Although estradiol was present in detectable quantities at oviposition, it was virtually undetectable by the early TSP. Testosterone showed no further decline after the early TSP. Progesterone continued to decline between the early and post-TSP. These results demonstrate that maternally derived yolk hormones decline at different rates. Alternative explanations for the disappearance of these yolk hormones are presented.
本研究调查了爬行动物卵黄中母体来源激素的潜在影响。具体而言，我们探究发育中的红耳龟（滑龟指名亚种）何时利用这些激素，红耳龟是一种具有温度依赖型性别决定（TSD）的物种。将卵分别在27摄氏度（产生雄性的温度）和31摄氏度（产生雌性的温度）下孵化。在发育的四个阶段测量孕酮、睾酮和17β-雌二醇的浓度：产卵时、温度敏感期（TSP）开始时、TSP结束时和孵化时。未检测到孵化温度对卵黄激素浓度有影响。所有三种激素在产卵时浓度最高。在整个发育过程中出现了激素特异性的下降模式。每种激素在产卵和TSP早期之间都有所下降。虽然产卵时雌二醇的含量可检测到，但在TSP早期几乎检测不到。睾酮在TSP早期之后没有进一步下降。孕酮在TSP早期和TSP后期之间持续下降。这些结果表明，母体来源的卵黄激素以不同速率下降。文中还给出了这些卵黄激素消失的其他解释。
