Research Group of Ethology, University of Antwerp, Wilrijk, Belgium.
PLoS One. 2011 Jan 25;6(1):e16326. doi: 10.1371/journal.pone.0016326.
Carotenoids are a class of pigments which are widely used by animals for the expression of yellow-to-red colour signals, such as bill or plumage colour. Since they also have been shown to promote immunocompetence and to function as antioxidants, many studies have investigated a potential allocation trade-off with respect to carotenoid-based signals within the context of sexual selection. Although an effect of carotenoids on non-visual (e.g. acoustic) signals involved in sexual selection has been hypothesized, this has to date not been investigated. First, we examined a potential effect of dietary carotenoid supplementation on overall song rate during the non-breeding season in captive male European starlings (Sturnus vulgaris). After only 3-7 days, we found a significant (body-mass independent) positive effect of carotenoid availability on overall song rate. Secondly, as a number of studies suggest that carotenoids could affect the modulation of sexual signals by plasma levels of the steroid hormone testosterone (T), we used the same birds to subsequently investigate whether carotenoid availability affects the increase in (nestbox-oriented) song rate induced by experimentally elevated plasma T levels. Our results suggest that carotenoids may enhance the positive effect of elevated plasma T levels on nestbox-oriented song rate. Moreover, while non-supplemented starlings responded to T-implantation with an increase in both overall song rate and nestbox-oriented song, carotenoid-supplemented starlings instead shifted song production towards (reproductively relevant) nestbox-oriented song, without increasing overall song rate. Given that song rate is an acoustic signal rather than a visual signal, our findings therefore indicate that the role of carotenoids in (sexual) signalling need not be dependent on their function as pigments.
类胡萝卜素是一类广泛存在于动物体内的色素，它们被用于表达黄色到红色的颜色信号，如鸟喙或羽毛的颜色。由于类胡萝卜素还被证明可以增强免疫能力并起到抗氧化剂的作用，因此许多研究都调查了在性选择的背景下，类胡萝卜素信号与分配之间的潜在权衡。尽管有人假设类胡萝卜素会影响性选择中涉及的非视觉（例如声学）信号，但迄今为止，这一假设尚未得到验证。首先，我们研究了饮食中类胡萝卜素补充对圈养雄性欧洲椋鸟（Sturnus vulgaris）在非繁殖季节总鸣唱率的潜在影响。仅 3-7 天后，我们发现类胡萝卜素可用性对总鸣唱率有显著的（与体重无关的）正向影响。其次，由于一些研究表明类胡萝卜素可能会通过类固醇激素睾酮（T）的血浆水平来影响性信号的调制，我们使用相同的鸟类来进一步研究类胡萝卜素的可用性是否会影响因血浆 T 水平升高而引起的（巢箱导向）鸣唱率的增加。我们的结果表明，类胡萝卜素可能会增强升高的血浆 T 水平对巢箱导向鸣唱率的正向影响。此外，未补充类胡萝卜素的椋鸟对 T 植入的反应是总鸣唱率和巢箱导向鸣唱率都增加，而补充类胡萝卜素的椋鸟则将鸣唱生产转向（与繁殖相关的）巢箱导向鸣唱，而不增加总鸣唱率。由于鸣唱率是一种声学信号而不是视觉信号，因此我们的发现表明，类胡萝卜素在（性）信号传递中的作用不一定依赖于它们作为色素的功能。
