Suzuki Kenta, Yamada Hiroko, Kobayashi Tetsuya, Okanoya Kazuo
Okanoya Emotional Information Project, Wako, Saitama, Japan.
J Exp Zool A Ecol Genet Physiol. 2012 Nov;317(9):561-70. doi: 10.1002/jez.1748. Epub 2012 Aug 27.
The Bengalese finch (BF; Lonchura striata var. domestica) is a domesticated strain of the white-backed munia (WBM; Lonchura striata). Environmental stresses activate the hypothalamic-pituitary-adrenal (HPA) axis and release corticosterone (CORT). We hypothesized that domesticated songbirds have reduced CORT levels because of reduced levels of environmental stresses (compared to wild conditions) and reductions in the role of CORT, which is necessary for survival in the wild. However, no study has examined the effects of domestication on songbird CORT levels. To explore the domestication effects, we compared CORT levels between domesticated BFs and their wild ancestors WBMs. We also compared CORT levels between bought and aviary-raised BFs, and between wild-caught and captive-raised WBMs to examine the influence of being raised. However, blood collection causes stress, which affects endocrine dynamics and makes continuous sampling difficult in small birds. Therefore, we used a non-invasive method to measure fecal CORT. Parallelism between diluted fecal extracts and a CORT standard, extraction efficiency, and ACTH challenge demonstrated the effectiveness of this method. This study demonstrates that BFs have lower fecal CORT than do WBMs, regardless of whether the WBMs were wild-caught or captive-raised. In addition, BFs sing more complex songs than WBMs. Considerable evidence suggests that song complexity is related to CORT levels. Previously, we found that the corticosteroid receptors were expressed in song-control areas of the BF brain. Based on these results, we hypothesize that reduced CORT levels through domestication might be one factor allowing for the development of more complex songs in BFs.
白腰文鸟（WBM；Lonchura striata）的家养品种是孟加拉雀（BF；Lonchura striata var. domestica）。环境压力会激活下丘脑 - 垂体 - 肾上腺（HPA）轴并释放皮质酮（CORT）。我们推测，家养鸣禽的CORT水平降低是因为环境压力水平降低（与野生环境相比）以及CORT作用的减弱，而CORT对野生环境中的生存是必需的。然而，尚无研究探讨驯化对鸣禽CORT水平的影响。为了探究驯化的影响，我们比较了家养孟加拉雀及其野生祖先白腰文鸟的CORT水平。我们还比较了购买的和笼养的孟加拉雀之间以及野生捕获的和圈养的白腰文鸟之间的CORT水平，以研究饲养方式的影响。然而，采血会造成压力，这会影响内分泌动态，并且在小鸟身上进行连续采样很困难。因此，我们采用了一种非侵入性方法来测量粪便中的CORT。稀释的粪便提取物与CORT标准品之间的平行性、提取效率以及促肾上腺皮质激素（ACTH）刺激试验证明了该方法的有效性。本研究表明，无论白腰文鸟是野生捕获的还是圈养的，孟加拉雀的粪便CORT水平都低于白腰文鸟。此外，孟加拉雀比白腰文鸟能唱出更复杂的歌曲。大量证据表明，歌曲复杂性与CORT水平有关。此前，我们发现皮质类固醇受体在孟加拉雀大脑的鸣叫控制区域表达。基于这些结果，我们推测驯化导致的CORT水平降低可能是孟加拉雀能够发展出更复杂歌曲的一个因素。
