Department of Biology, Portland State University, P.O. Box 751, Portland, OR 97207-0751, USA.
Gen Comp Endocrinol. 2011 Nov 1;174(2):166-74. doi: 10.1016/j.ygcen.2011.08.016. Epub 2011 Aug 30.
The annual killifish, Austrofundulus limnaeus, typically enters embryonic diapause at two distinct points of development, termed diapause II and III. This study explores the role of maternal and embryonic steroid hormones, including 17-β-estradiol (E2), androstenedione (A4) and testosterone (T), in regulating the developmental decision to enter or escape diapause II. Steroid hormone levels were measured in tissues isolated from adult female killifish during the normal lifespan of this species and in individuals of the same age that were producing either high or low proportions of escape embryos. Levels of steroid hormones were also measured during early development and in fertilized eggs that were predicted to be on either an escape or diapausing developmental trajectory. Decreases in maternal E2 levels associated with age are correlated with decreasing escape embryo production. Maternal production of escape embryos is correlated with increased ratios of E2 to T in adult ovary tissue. Interestingly, neither hormone is significantly different in fish producing embryos on different developmental pathways when examined independently. Levels of steroid hormones in fertilized eggs are not correlated with entry or escape from diapause II, though levels of A4 tend to be higher in escape embryos. Escape embryos exhibit faster hormone metabolism and earlier hormone synthesis than embryos that will enter diapause II. Incubation of embryos in exogenous E2 is associated with a 7-fold increase in escape embryo production, and significantly elevated A4 levels. These data suggest that steroid hormones may be critical factors involved in determining developmental pathways in embryos of A. limnaeus.
一年生花鳉鱼，Austrofundulus limnaeus，通常在两个不同的发育点进入胚胎休眠，分别称为休眠 II 和休眠 III。本研究探讨了母体和胚胎类固醇激素（包括 17-β-雌二醇（E2）、雄烯二酮（A4）和睾酮（T））在调节进入或逃避休眠 II 的发育决策中的作用。在该物种的正常寿命期间，从成年雌性花鳉鱼的组织中测量了类固醇激素水平，以及处于产生高或低比例逃避胚胎的个体的组织中测量了类固醇激素水平。还在早期发育期间以及在预测处于逃避或休眠发育轨迹的受精卵中测量了类固醇激素水平。与年龄相关的母体 E2 水平下降与逃避胚胎产生量的减少有关。母体逃避胚胎的产生与成年卵巢组织中 E2 与 T 的比值增加有关。有趣的是，当单独检查时，两种激素在产生不同发育途径胚胎的鱼类中均无显着差异。受精卵中的类固醇激素水平与进入或逃避休眠 II 无关，尽管 A4 水平在逃避胚胎中往往较高。逃避胚胎表现出比将进入休眠 II 的胚胎更快的激素代谢和更早的激素合成。胚胎在体外孵育 E2 会导致逃避胚胎产生量增加 7 倍，并显著提高 A4 水平。这些数据表明，类固醇激素可能是决定 A. limnaeus 胚胎发育途径的关键因素。
