Dissertation Research: A Functional and Mechanistic Investigation of Yolk Androgens in the European Starling (Sturnus Vulgaris)

论文研究：欧洲八哥(Sturnus Vulgaris)、伊丽莎白·阿德金斯-里根(Elizabeth Adkins-Regan)和凯文·皮尔兹雌鸟(Kevin Pilz Female)卵黄雄激素的功能和机制研究在它们的蛋黄中储存类固醇激素，如睾酮。在人工饲养的金丝雀中，高水平的蛋黄睾酮会导致从这些蛋中孵化出来的雏鸟的生长速度和乞讨行为的提高。目前还没有关于蛋黄激素对其他鸟类的行为影响的信息。也没有确凿的证据表明，雌性在不同的生态环境下在卵子中沉积不同水平的荷尔蒙，以最大限度地提高其繁殖成功。这项研究试图通过研究两种类型的卵黄雄激素来填补我们知识上的空白，一种是睾酮，另一种是一种相关的激素，称为雄烯二酮，在野生生活的欧洲八哥(Sturnus Common Garis)中。这项研究的第一个目标是证明卵黄雄激素对欧洲八哥雏鸟生长和行为的影响。鸡蛋将被注射激素或控制液，小鸡的生长和乞讨行为将被监测，直到小鸡准备离开鸟巢。这项研究的第二个目标是检验这一假设，即参与幼虫寄生繁殖策略的雌性在其卵子中积累了高水平的卵黄雄激素。一只寄生幼鸟的雌性在其他雌性的巢中产卵，以避免自己抚养幼鸟；八哥有时会寄生在其他八哥身上。如果卵黄雄激素导致雏鸟通过更多的乞求和更快的生长来更多地竞争，那么产卵寄生卵的雌性应该在这些卵中沉积高水平的雄激素，这样她的雏鸟就能够自私地竞争它们不相关的筑巢伙伴。这项研究的第三个目标是检查女性的特征，如身体大小和年龄是否与女性在卵子中沉积的卵黄雄激素水平有关。这一数据将被用来确定幼虫寄生雌性的小体型和年轻年龄是否可以解释为什么幼虫寄生卵含有高水平的卵黄雄激素。这一数据还将被用来检验这样一个假设，即“高质量”雌性(较大、较年长的雌性)应该比“低质量”雌性在卵子中投入更多的卵黄雄激素。总而言之，这项研究将在单一物种的野生鸣禽中调查：1)卵黄雄激素对雏鸟的影响；2)雌性是否以有利于其繁殖成功的方式将雄激素分配给卵；以及3)雌性卵黄雄激素的分配是否会随着雌性特征的变化而变化，如体型和年龄。这项研究将增加我们对荷尔蒙对鸟类发育影响的知识，并提供对雌性能够适应性地操纵后代特征的非遗传手段的理解。这项研究也可能作为哺乳动物物种母体荷尔蒙对后代发育影响的模型。

Dissertation Research: A Functional and Mechanistic Investigation of Yolk Androgens in the European Starling (Sturnus Vulgaris)Elizabeth Adkins-Regan and Kevin PilzFemale birds deposit steroid hormones, such as testosterone, in the yolks of their eggs. In captive-bred canaries, high levels of "yolk testosterone" in eggs cause elevated growth rates and begging behavior in the chicks that hatch from those eggs. There is currently no information regarding the behavioral effects of yolk hormones in other species of birds. Nor is there well-substantiated evidence that females deposit different levels of hormones in eggs under different ecological circumstances to maximize their reproductive success. This study intends to fills these gaps in our knowledge by studying two types of "yolk androgens", one being testosterone and the other being a related hormone called androstenedione, in wild-living European starlings (Sturnus vulgaris). The first goal of this research is to document the effects of yolk androgens on European starling chick growth and behavior. Eggs will be injected with hormone or with a control solution and the growth and begging behavior of the chicks will be monitored until the chicks are ready to leave the nest. The second goal of this research is to test the hypothesis that females who engage in the reproductive strategy of brood parasitism deposit high levels of yolk androgens in their eggs. A brood parasite female lays her eggs in the nests of other females to avoid raising the chicks herself; starlings sometimes brood parasitize other starlings. If yolk androgens cause chicks to compete more, by begging more and growing faster, then a female who lays brood parasitic eggs should deposit high levels of androgen in those eggs so that her chicks will be able to selfishly outcompete their unrelated nestmates. The third goal of this research is to examine whether female characteristics such as body size and age are related to the levels of yolk androgens that females deposit in eggs. This data will be used to determine if the small size and young age of brood parasitic females may explain why brood parasitic eggs have high levels of yolk androgens. This data will also be used to test the hypothesis that "high quality" females (larger, older females) should invest more yolk androgens in eggs than "low quality" females. In summary, this research will investigate within a single species of wild songbird, 1) the effects of yolk androgens on chicks; 2) whether females allocate androgens to eggs in ways which benefit their reproductive success; and 3) whether female allocation of yolk androgens varies with female characteristics such as body size and age. This research will increase our knowledge of hormone effects on development in birds and provide understanding of non-genetic means by which females can adaptively manipulate offspring characteristics. The research may also be useful as a model of maternal hormone effects on developing offspring in mammalian species.