Wingfield J C, Goldsmith A R
Department of Zoology, University of Washington, Seattle 98195.
Horm Behav. 1990 Mar;24(1):89-103. doi: 10.1016/0018-506x(90)90029-w.
Plasma levels of testosterone (T), estradiol (E2), and prolactin were measured in samples collected from free-living song sparrows, Melospiza melodia. In males, plasma levels of T were elevated early in the season when territories were established and when females laid the first clutch of eggs. Thereafter, T levels declined and remained low throughout the remainder of the breeding cycle. However, if the first brood was lost to a predator, or by experimental removal of the nest, plasma levels of T increased as renesting, to replace the clutch, occurred. Circulating levels of prolactin in males began to rise during the egg-laying stage of the first brood, reached a maximum toward the end of the incubation stage, remained elevated until breeding was terminated, and then declined throughout the moulting stage to basal values in October. Prolactin levels remained high throughout the breeding season irrespective of whether a brood was raised successfully or whether the nest was lost and renesting occurred. In females, plasma levels of E2 were elevated prior to the egg-laying stage for each brood as is typical of multiple-brooded species. However, prolactin titers rose dramatically during egg-laying for the first clutch (slightly higher than in males) and were maximal by onset of incubation. Only females of this species incubate, although males do feed young. As in males, plasma prolactin in females remained high between broods and during experimentally induced renesting, and then declined to basal by the end of the moult stage in October. These data suggest that there are no differences in the temporal patterns of prolactin concentrations in blood between multiple-brooding and renesting. In a separate experiment, captive male song sparrows were transferred from a short day to artificial long days (18L 6D) and a control group was maintained on 9L 15D. In the long-day group, prolactin levels rose abruptly over the first 20 days, as the testes developed, and remained high well into postnuptial moult after the gonads had regressed. Prolactin remained basal in the control group. These data suggest that the temporal pattern of circulating prolactin levels throughout the breeding season is regulated at least partly by changing photoperiod. However, nonphotoperiodic factors are also important since photoperiodically induced increases in prolactin are significantly less than those seen in free-living individuals. These differences may be related to parental behavior.
从自由生活的歌带鹀（Melospiza melodia）采集的样本中，测量了睾酮（T）、雌二醇（E2）和催乳素的血浆水平。在雄性中，当领地建立且雌鸟产下第一窝卵时，血浆T水平在季节早期升高。此后，T水平下降，并在繁殖周期的剩余时间内保持在低水平。然而，如果第一窝雏鸟被捕食者吃掉，或者通过实验移除鸟巢，随着重新筑巢以替换卵，血浆T水平会升高。雄性催乳素的循环水平在第一窝卵的产卵阶段开始上升，在孵化阶段结束时达到最高值，在繁殖结束前一直保持升高，然后在换羽阶段下降至10月份的基础值。无论一窝雏鸟是否成功养育，或者鸟巢是否丢失并重新筑巢，催乳素水平在整个繁殖季节都保持在高位。在雌性中，如多窝繁殖物种的典型情况一样，每窝卵的产卵阶段之前血浆E2水平都会升高。然而，第一窝卵产卵期间催乳素滴度急剧上升（略高于雄性），并在孵化开始时达到最大值。只有该物种的雌性会孵化，尽管雄性会喂养幼鸟。与雄性一样，雌性血浆催乳素在各窝之间以及实验诱导的重新筑巢期间保持高位，然后在10月份换羽阶段结束时降至基础水平。这些数据表明，多窝繁殖和重新筑巢之间血液中催乳素浓度的时间模式没有差异。在另一个实验中，将圈养的雄性歌带鹀从短日照转移到人工长日照（18小时光照 6小时黑暗），并将一个对照组维持在9小时光照 15小时黑暗条件下。在长日照组中，随着睾丸发育，催乳素水平在最初20天内急剧上升，并在性腺退化后的婚后换羽期一直保持高位。催乳素在对照组中保持在基础水平。这些数据表明，整个繁殖季节循环催乳素水平的时间模式至少部分受光周期变化调节。然而，非光周期因素也很重要，因为光周期诱导的催乳素增加明显低于自由生活个体中的情况。这些差异可能与亲代行为有关。
