*Department of Zoology, Oklahoma State University, Stillwater, OK 74078, USA.
Integr Comp Biol. 2008 Sep;48(3):428-36. doi: 10.1093/icb/icn058. Epub 2008 Jun 9.
Steroids present in egg yolk have been shown to vary as a result of numerous social and environmental influences and to produce both positive and negative phenotypic outcomes in offspring. In the present study, we examined how quality of the diet affects plasma and yolk steroids in the green anole (Anolis carolinensis), a lizard species with genotypic sex determination. We documented the effects of body condition on plasma testosterone (T) and corticosterone (CORT)-steroids with frequently opposing effects-in breeding females and on the T and CORT content of their eggs. We chose to manipulate body condition via diet because resource availability is a relevant, fluctuating variable in the environment to which females can be expected to respond. Field-collected females were housed in the laboratory and kept on either a reduced, standard, or enhanced diet (differing in nutritional quality and/or quantity) for ten weeks. Although females did not differ in body condition at the beginning of the study, we found these diet regimes effective in producing females that differed in condition by the end of the study. Females on diets of enhanced quality were in better condition, produced more, but not heavier, eggs, and had higher plasma T concentrations than did females on a standard diet or one of reduced quality. There was also a significant positive relationship between laying sequence of eggs and yolk T for females on diets of enhanced quality, but not for the females on diets of standard or reduced quality. There were no effects of quality of diet on CORT in plasma or yolk, but yolk T and yolk CORT exhibited a strong positive correlation irrespective of treatment. Females on diets of reduced quality did not differ from females on standard diets either with respect to reproductive output or to endocrine profiles, in spite of being in worse body condition. These results demonstrate that females' body condition, physiology, and reproductive output can be manipulated by quality of diet, and that changes in deposition of yolk steroids in response to diet may be minimal.
蛋黄中的类固醇会因受到许多社会和环境因素的影响而发生变化，并对后代产生积极和消极的表型结果。在本研究中，我们研究了饮食质量如何影响绿安乐蜥（Anolis carolinensis）的血浆和蛋黄类固醇，这是一种具有基因型性别决定的蜥蜴物种。我们记录了身体状况对繁殖雌性血浆中睾丸激素（T）和皮质酮（CORT）-具有相反作用的类固醇-及其卵中的 T 和 CORT 含量的影响。我们选择通过饮食来操纵身体状况，因为资源的可利用性是环境中一个相关的、波动的变量，雌性可以预期对其做出反应。从野外收集的雌性被安置在实验室中，并让它们在低、标准或高（营养质量和/或数量不同）饮食中饲养十周。尽管雌性在研究开始时的身体状况没有差异，但我们发现这些饮食方案在研究结束时有效地产生了在身体状况上存在差异的雌性。饮食质量较高的雌性身体状况更好，产卵数量更多，但卵的重量没有增加，并且血浆 T 浓度高于标准饮食或低质量饮食的雌性。在饮食质量较高的雌性中，产卵顺序与蛋黄 T 之间也存在显著的正相关关系，但在饮食质量标准或较低的雌性中则没有。饮食质量对血浆或蛋黄中的 CORT 没有影响，但无论治疗如何，蛋黄 T 和蛋黄 CORT 均表现出强烈的正相关关系。在身体状况较差的情况下，低质量饮食的雌性与标准饮食的雌性在生殖输出或内分泌谱方面没有差异。这些结果表明，雌性的身体状况、生理机能和生殖输出可以通过饮食质量来操纵，并且对饮食的反应中蛋黄类固醇的沉积变化可能很小。
