Casagrande Stefania, Pinxten Rianne, Zaid Erika, Eens Marcel
Department of Biology, Ethology Group, University of Antwerp, Campus Drie Eiken, Antwerp, Belgium.
Department of Biology, Ethology Group, University of Antwerp, Campus Drie Eiken, Antwerp, Belgium; Institute for Education and Information Sciences, Research Unit Didactica, University of Antwerp, Antwerp, Belgium.
PLoS One. 2014 Dec 30;9(12):e115899. doi: 10.1371/journal.pone.0115899. eCollection 2014.
Despite the appealing hypothesis that carotenoid-based colouration signals oxidative status, evidence supporting the antioxidant function of these pigments is scarce. Recent studies have shown that lutein, the most common carotenoid used by birds, can enhance the expression of non-visual traits, such as birdsong. Nevertheless, the underlying physiological mechanisms remain unclear. In this study we hypothesized that male European starlings (Sturnus vulgaris) fed extra lutein increase their song rate as a consequence of an improved oxidative status. Although birdsong may be especially sensitive to the redox status, this has, to the best of our knowledge, never been tested. Together with the determination of circulating oxidative damage (ROMs, reactive oxygen metabolites), we quantified uric acid, albumin, total proteins, cholesterol, and testosterone, which are physiological parameters potentially sensitive to oxidation and/or related to both carotenoid functions and birdsong expression. We found that the birds fed extra lutein sang more frequently than control birds and showed an increase of albumin and cholesterol together with a decrease of oxidative damage. Moreover, we could show that song rate was associated with high levels of albumin and cholesterol and low levels of oxidative damage, independently from testosterone levels. Our study shows for the first time that song rate honestly signals the oxidative status of males and that dietary lutein is associated with the circulation of albumin and cholesterol in birds, providing a novel insight to the theoretical framework related to the honest signalling of carotenoid-based traits.
尽管基于类胡萝卜素的羽色信号表明氧化状态这一假设颇具吸引力，但支持这些色素具有抗氧化功能的证据却很少。最近的研究表明，叶黄素是鸟类最常用的类胡萝卜素，它可以增强非视觉特征的表达，比如鸟鸣。然而，其潜在的生理机制仍不清楚。在本研究中，我们假设额外摄入叶黄素的雄性欧洲椋鸟（Sturnus vulgaris）由于氧化状态的改善而提高其鸣叫速率。尽管鸟鸣可能对氧化还原状态特别敏感，但据我们所知，这从未得到过验证。我们在测定循环氧化损伤（活性氧代谢产物，即ROMs）的同时，还对尿酸、白蛋白、总蛋白、胆固醇和睾酮进行了量化，这些都是可能对氧化敏感和/或与类胡萝卜素功能及鸟鸣表达相关的生理参数。我们发现，额外摄入叶黄素的鸟类比对照鸟类鸣叫更频繁，并且白蛋白和胆固醇增加，氧化损伤减少。此外，我们可以证明，鸣叫速率与高水平的白蛋白和胆固醇以及低水平的氧化损伤相关，与睾酮水平无关。我们的研究首次表明，鸣叫速率真实地反映了雄性的氧化状态，并且膳食叶黄素与鸟类体内白蛋白和胆固醇的循环有关，为与基于类胡萝卜素特征的诚实信号相关的理论框架提供了新的见解。
