Department of Biology, Shepherd University, Shepherdstown, WV 25425, USA.
Department of Biology, Shepherd University, Shepherdstown, WV 25425, USA.
Comp Biochem Physiol B Biochem Mol Biol. 2021 Apr-May;253:110546. doi: 10.1016/j.cbpb.2020.110546. Epub 2020 Dec 18.
Carotenoid-colored integuments commonly function as sexually selected honest signals because carotenoid pigments can be costly to obtain, ingest, absorb, metabolize or transport before being deposited into the integument. As such, carotenoid pigmentation is often sexually dichromatic, with males being more colorful than females. Sexual dichromatism may also occur in ultraviolet (UV) wavelengths, which is visible to organisms who possess UV-sensitive photoreceptors. The stripes and spots of painted turtles (Chrysemys picta) are carotenoid-based and reflect UV wavelengths. This research describes UV sexual dichromatism in painted turtles and shows how carotenoid deprivation changes spot and stripe color in male and female painted turtles. Adult turtles were fed a diet that was supplemented with carotenoids (i.e., C diet) or deprived of carotenoids (C-). Stripe and spot color were measured with UV-vis spectrometry, and blood was drawn from all turtles before and after the dietary treatment. HPLC analysis revealed five carotenoids (4 xanthophylls and beta-carotene) circulating in turtle blood. C-diet reduced yellow chroma and increased brightness of yellow and red stripes or spots, relative to the C diet, but there was no sexually dimorphic effect of carotenoid deprivation on color, nor did carotenoid deprivation affect UV reflectance. Carotenoid deprivation reduced all circulating carotenoids, but beta-carotene was the only pigment with a significant effect on post-experimental carotenoids, implying that changes in color were due in part to reduction in circulating levels of beta-carotene. Color generation appears to be complex in turtles and have dietary as well as non-dietary components.
带颜色的角质鳞片通常作为性选择的诚实信号，因为类胡萝卜素色素在沉积到角质鳞片之前，获取、摄入、吸收、代谢或运输都需要付出代价。因此，类胡萝卜素色素通常是两性异形的，雄性比雌性更有色彩。性二色性也可能发生在紫外线 (UV) 波长，具有 UV 敏感感光器的生物可以看到 UV 波长。彩绘龟（Chrysemys picta）的条纹和斑点是基于类胡萝卜素的，并且反射 UV 波长。这项研究描述了彩绘龟的 UV 性二色性，并展示了类胡萝卜素剥夺如何改变雄性和雌性彩绘龟的斑点和条纹颜色。成年龟喂食补充类胡萝卜素的饮食（即 C 饮食）或剥夺类胡萝卜素（C-）。使用 UV-vis 光谱法测量条纹和斑点的颜色，并在饮食处理前后从所有海龟中抽取血液。HPLC 分析显示五种类胡萝卜素（4 种叶黄素和β-胡萝卜素）在龟血中循环。与 C 饮食相比，C 饮食降低了黄色色度并增加了黄色和红色条纹或斑点的亮度，但类胡萝卜素剥夺对颜色没有性别二态效应，也没有影响 UV 反射率。类胡萝卜素剥夺减少了所有循环类胡萝卜素，但β-胡萝卜素是对实验后类胡萝卜素具有显著影响的唯一色素，这意味着颜色的变化部分是由于循环β-胡萝卜素水平降低所致。颜色的产生在龟类中似乎很复杂，既有饮食因素，也有非饮食因素。
