Hews D K, Moore M C
Department of Zoology, Arizona State University, Tempe 85287-1501.
Gen Comp Endocrinol. 1995 Jan;97(1):86-102. doi: 10.1006/gcen.1995.1009.
Vertebrates species vary in the degree to which the sexes differ in their expression of secondary sex characters, which can be expressed in one sex but not the other, fully expressed in both sexes, or expressed to different degrees in the two sexes. Sex steroid hormones contribute to the development of sex differences, either through action early in life (organization), following sexual maturation (activation), or both. However, relatively little is known about the contributions of sex steroid hormones to species-level variation in sexual dimorphism. We began to address this by assessing in tree lizards, Urosaurus ornatus, the effects of testosterone (T) and dihydrotestosterone (DHT) on expression of the male-typical traits: femoral pore secretions, accessory sex tissues, patches of ventrolateral blue, intensity and hue of throat color, and body size. We administered long-lasting hormone implants of these androgens to intact or ovariectomized adult females, intact hatchling females, and intact hatchling males to determine the relative contribution of organizational and activational influences of androgens on sexual differentiation of these traits. Waxy femoral pore secretions and full intensity of the orange background color of the throat fan (dewlap) required only activation and both androgens were equally effective. Both androgens caused hypertrophy of accessory tissues associated with the hemipenes, but only in hatchling males. Full expression of ventrolateral blue patches required organization by DHT. Androgens had complex organizational actions on growth. In the doses used in the experiment, DHT inhibited body-length growth but not mass growth of hatchling males. Only T inhibited the growth (length and mass) of hatchling females. Because earlier work found that castration also reduced the growth of hatchling males, the organizational effects of androgen on growth might be dose-related. Results for hormonal control of dewlap type were complex. In this population dewlap color is solid orange in females, but polymorphic in males with 50% expressing solid orange (O) and 50% orange-blue (orange with a central blue patch, OB). These color morphs represent permanent male alternatives: OB males are territorial and more aggressive than O males who do not defend territories. Results of the hormone manipulations are most consistent with the interpretation that dewlap morph type requires both organization and activation by androgen. T appears to be more important in organizing morph differences, whereas DHT appears to be more important in activating expression of underlying morph differences. Females only expressed male-typical OB dewlaps when given DHT, and only about 50% did so.
脊椎动物物种在两性间第二性征表达的差异程度上各不相同，这些特征可能在一种性别中表达而在另一种性别中不表达，在两性中都完全表达，或者在两性中表达程度不同。性类固醇激素通过生命早期的作用（组织作用）、性成熟后的作用（激活作用）或两者共同作用，促进性别差异的发育。然而，关于性类固醇激素对两性异形的物种水平变异的贡献，人们了解得相对较少。我们通过评估雄性典型特征在树蜥（饰纹强棱蜥）中的表达，来着手解决这个问题，这些特征包括股孔分泌物、附属生殖组织、腹侧蓝色斑块、喉部颜色的强度和色调以及体型大小，我们将这些雄激素的长效激素植入物施用于完整的或卵巢切除的成年雌性、完整的幼体雌性和完整的幼体雄性，以确定雄激素的组织作用和激活作用对这些特征性分化的相对贡献。蜡状股孔分泌物和喉部扇（喉囊）橙色背景颜色的完全强度只需要激活作用，两种雄激素的效果相同。两种雄激素都会导致与半阴茎相关的附属组织肥大，但仅在幼体雄性中出现这种情况。腹侧蓝色斑块的完全表达需要双氢睾酮的组织作用。雄激素对生长有复杂的组织作用。在实验中使用的剂量下，双氢睾酮抑制幼体雄性的体长生长，但不抑制体重生长。只有睾酮抑制幼体雌性的生长（体长和体重）。因为早期的研究发现阉割也会减少幼体雄性的生长，雄激素对生长的组织作用可能与剂量有关。喉部扇类型的激素控制结果很复杂。在这个种群中，雌性的喉囊颜色是纯橙色，但雄性的喉囊颜色是多态的，50%的雄性表达纯橙色（O），50%的雄性表达橙蓝色（橙色中央有蓝色斑块，OB）。这些颜色形态代表了雄性的永久性差异：OB雄性具有领地意识，比不保卫领地的O雄性更具攻击性。激素处理的结果最符合这样的解释，即喉囊形态类型既需要雄激素的组织作用也需要激活作用。睾酮在组织形态差异方面似乎更重要，而双氢睾酮在激活潜在形态差异的表达方面似乎更重要。雌性只有在给予双氢睾酮时才会表达雄性典型的OB喉囊，而且只有约50%的雌性会这样。
