Villavicencio Camila P, Windley Harriet, D'Amelio Pietro B, Gahr Manfred, Goymann Wolfgang, Quispe René
Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Eberhard-Gwinner-Str. 6a, D-82319, Seewiesen, Germany.
Department of Ecological Science, Institute of Ecology and Biodiversity, Faculty of Science, University of Chile, Las Palmeras 3425, Ñuñoa, Santiago, Chile.
Front Zool. 2021 Feb 24;18(1):8. doi: 10.1186/s12983-021-00389-x.
The connection between testosterone and territoriality in free-living songbirds has been well studied in a reproductive context, but less so outside the breeding season. To assess the effects of seasonal androgenic action on territorial behavior, we analyzed vocal and non-vocal territorial behavior in response to simulated territorial intrusions (STIs) during three life-cycle stages in free-living male black redstarts: breeding, molt and nonbreeding. Concurrently, we measured changes in circulating testosterone levels, as well as the mRNA expression of androgen and estrogen receptors and aromatase in the preoptic, hypothalamic and song control brain areas that are associated with social and vocal behaviors.
Territorial behavior and estrogen receptor expression in hypothalamic areas did not differ between stages. But plasma testosterone was higher during breeding than during the other stages, similar to androgen receptor and aromatase expression in the preoptic area. The expression of androgen receptors in the song control nucleus HVC was lower during molt when birds do not sing or sing rarely, but similar between the breeding and the nonbreeding stage. Nevertheless, some song spectral features and the song repertoire differed between breeding and nonbreeding. Territorial behavior and song rate correlated with the expression of steroid receptors in hypothalamic areas, and in the song control nucleus lMAN.
Our results demonstrate seasonal modulation of song, circulating testosterone levels, and brain sensitivity to androgens, but a year-round persistency of territorial behavior and estrogen receptor expression in all life-cycle stages. This suggests that seasonal variations in circulating testosterone concentrations and brain sensitivity to androgens is widely uncoupled from territorial behavior and song activity but might still affect song pattern. Our study contributes to the understanding of the complex comparative neuroendocrinology of song birds in the wild.
在自由生活的鸣禽中，睾酮与领地行为之间的联系在繁殖背景下已得到充分研究，但在繁殖季节之外的研究较少。为了评估季节性雄激素作用对领地行为的影响，我们分析了自由生活的雄性黑喉红尾鸲在三个生命周期阶段（繁殖期、换羽期和非繁殖期）对模拟领地入侵（STIs）的发声和非发声领地行为。同时，我们测量了循环睾酮水平的变化，以及与社会和发声行为相关的视前区、下丘脑和发声控制脑区中雄激素、雌激素受体和芳香化酶的mRNA表达。
下丘脑区域的领地行为和雌激素受体表达在各阶段之间没有差异。但繁殖期的血浆睾酮水平高于其他阶段，类似于视前区雄激素受体和芳香化酶的表达。在换羽期，当鸟类不唱歌或很少唱歌时，发声控制核团HVC中的雄激素受体表达较低，但在繁殖期和非繁殖期之间相似。然而，繁殖期和非繁殖期的一些歌声频谱特征和曲目不同。领地行为和歌声速率与下丘脑区域以及发声控制核团lMAN中类固醇受体的表达相关。
我们的结果表明，歌声、循环睾酮水平和大脑对雄激素的敏感性存在季节性调节，但在所有生命周期阶段，领地行为和雌激素受体表达全年持续存在。这表明循环睾酮浓度和大脑对雄激素的敏感性的季节性变化与领地行为和歌声活动广泛脱钩，但仍可能影响歌声模式。我们的研究有助于理解野生鸣禽复杂的比较神经内分泌学。
