Circulating levels of luteinizing hormone and steroid hormones in relation to social status in the cooperatively breeding white‐browed sparrow weaver, Plocepasser mahali
Circulating levels of luteinizing hormone and steroid hormones in relation to social status in the cooperatively breeding white‐browed sparrow weaver, Plocepasser mahali
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DOI：
10.1111/j.1469-7998.1991.tb03800.x
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发表时间：
1991-09
影响因子：
2
通讯作者：
J. Wingfield;R. Hegner;D. Lewis
中科院分区：
文献类型：
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作者：
J. Wingfield;R. Hegner;D. Lewis
我们已经开始对半干旱热带环境下调节合作育种的环境和内分泌机制进行了一系列深入的研究。在赞比亚（13dG S）卢安瓜山谷尼亚玛鲁玛营地附近的一个野外地点，研究了一个有颜色标记的白眉毛编织麻雀（Plocepasser mahali）种群。这个物种从10月到4月繁殖，尽管有些幼崽可能早在8月就被发现，幼崽可能被喂养到5月。采用非破坏性技术监测性腺发育、体重和脂肪储备的年度周期，并收集少量血液样本来测量生殖激素和皮质酮的循环水平。所有个体在抽样后释放，并通过系统的行为观察记录社会和生殖活动。因此，每个个体可以被确定为：(1)有繁殖能力的成年个体；(2)有亲缘关系的帮助者（即在种群内繁殖的雄性和雌性的后代）；或者(3)非亲属（=入侵者）帮手（这些鸟帮助保卫领土，但不帮助哺育幼鸟；它们与繁殖对没有关系，通常来自群体外）。与亲缘帮助者和外来帮助者相比，育龄雄性的睾丸更大，睾酮水平也更高。在雌性中，所有地位组的卵泡直径都达到2毫米，但只有繁殖雌性排卵。除在繁殖季节的前半段，雌性入侵帮助者体内的黄体生成素（LH）含量较高外，其他生殖激素水平在不同地位的雌性之间无显著差异。虽然血浆睾酮水平在繁殖雄性中最高，但最高滴度比温带雀形目雄性低两个数量级。此外，注射一种肽激素GnRH（促性腺激素释放激素）会增加男性和女性的血浆LH水平，随后只有男性的睾丸激素水平升高，但没有超过2月份的正常最大值。gnrh诱导的高黄体生成素水平不影响女性血液中的睾酮浓度。目前的研究结果表明，激素对白眉织雀攻击行为的控制与对北温带物种的调查预测不同。这些现象是否是热带物种的典型现象，特别是合作育种者的典型现象，还有待确定。由于世界上大多数鸟类生活在热带地区，其中很大一部分是合作繁殖的，因此需要更多的研究来建立繁殖行为和合作繁殖的激素基础。考虑到已经收集到的基线数据，白眉编织麻雀将是一个有用的模型。
We have begun an intensive series of investigations into the environmental and endocrine mechanisms regulating cooperative breeding in a semi-arid tropical environment. A colour-marked population of white-browed sparrow weavers (Plocepasser mahali) was studied at a field site near Nyamaluma Camp, Luangwa Valley, Zambia (13dG S). This species breeds from October to April, although some clutches may be found as early as August and young may be fed until May. Non-disruptive techniques were employed to monitor annual cycles of gonadal development, body mass and fat reserves, and small blood samples were collected to measure circulating levels of reproductive hormones and corticosterone. All individuals were released after sampling and the social and reproductive activities recorded by systematic behavioural observations. Each individual could thus be identified as: (1) a breeding adult; (2) a related helper (i.e. offspring of the breeding male and female within the group); or (3) a non-related (=invader) helper (these birds helped defend territory but did not help feed young; they were not related to the breeding pair and usually originated from outside the group). Breeding males had larger testes and higher levels of testosterone than either related helpers or invader helpers. In females, all status groups had follicles up to 2 mm in diameter, but only breeding females ovulated. There were no differences in plasma levels of reproductive hormones among different status females, except for higher circulating luteinizing hormone (LH) in invader female helpers during the first part of the breeding season. Although plasma levels of testosterone were highest in breeding males, the maximum titres were two orders of magnitude less than in males of passerine species from temperate regions. Furthermore, injections of a peptide hormone GnRH (gonadotropin-releasing hormone) increased plasma LH levels in both males and females, and were followed by rises in testosterone levels only in males, but not over the normal maximum seen in February. GnRH-induced high levels of LH did not affect testosterone concentrations in the blood of females. Results obtained thus far indicate that the hormonal control of aggression in white-browed sparrow weavers is different from that predicted by investigations on north temperate species. Whether these phenomena are typical of tropical species, particularly cooperative breeders, remains to be determined. Since most of the world's species of birds live in the tropics, and a substantial fraction of them breed cooperatively, more investigations are needed to establish the hormonal basis of reproductive behaviour and cooperative breeding. Given the baseline data already collected, the white-browed sparrow weaver will be a useful model.