Eagleson G W, McKeown B A
Biochem Exp Biol. 1980;16(2):111-26.
In order to determine the factors affecting the maturation of the functional hypothalamo-pituitary-thyroid axis, Ambystoma gracile (Baird) larvae of different ages and acclimated to different temperature regimes were exposed to a concentration of thyroxine (T4) which activates the pituitary-thyroid axis. A. gracile from a montane and low-altitude population were utilized. These studies, plus observations concerning spontaneous metamorphosis, indicated that populations of Ambystoma gracile are highly polymorphic as suggested by Sprules (1974 b). A. gracile populations consist of 'obligate transformers', 'obligate neotenes', and 'facultative transformers'--which will metamorphose depending on environmental conditions. The colder high-altitude conditions tend to select against facultative individuals, whereas the less certain low-altitude conditions permit a much higher proportion of animals that exhibit a facultative response with respect to metamorphosis. Interrelationships between environment and physiological parameters that determine morphology in salamanders are discussed with regard to these findings.
为了确定影响功能性下丘脑 - 垂体 - 甲状腺轴成熟的因素，将不同年龄且适应不同温度环境的细口钝口螈（Baird）幼体暴露于能激活垂体 - 甲状腺轴的甲状腺素（T4）浓度下。使用了来自山区和低海拔种群的细口钝口螈。这些研究以及关于自发变态的观察表明，细口钝口螈种群具有高度多态性，正如斯普鲁尔斯（1974b）所指出的那样。细口钝口螈种群由“专性变态者”、“专性幼态持续者”和“兼性变态者”组成——兼性变态者会根据环境条件发生变态。较寒冷的高海拔环境往往不利于兼性个体，而不确定性较高的低海拔环境则允许更高比例的动物在变态方面表现出兼性反应。结合这些发现，讨论了环境与决定蝾螈形态的生理参数之间的相互关系。
