Centre of Excellence in Evolutionary Research, Department of Biological and Environmental Sciences, University of Jyväskylä, P.O. Box 35, FI-40014 Jyväskylä, Finland.
Zoology (Jena). 2011 Jun;114(3):129-39. doi: 10.1016/j.zool.2011.01.003. Epub 2011 Jun 17.
Male secondary sexual characters, such as color patterns, are often investigated at the macroscale level. However, micro- and nanoscale levels of morphological investigations may reveal functional features responsible for a particular coloration, thus providing more information, e.g., about the condition dependence of male sexual characters. The aim of this paper was to investigate cuticle color and its structure in males of two congeneric damselfly species, Calopteryx splendens and Calopteryx virgo, and reveal possible color changes with age. According to spectrometer measurements, C. splendens males were bluer and had a greater saturation of blue in their abdomen than C. virgo males, which were, in turn, greener and had more green saturation. Although the two species differed in the number of structural layers and the spacing of the layers, it seems that intactness of the wax crystals covering the epicuticle was most often the morphological trait which was related to the color parameters measured from males' cuticles. The effect of the crystalline wax coverage on cuticle color was also confirmed by removing the wax using chloroform: after the treatment, the hue was bluer, the cuticle had a greater brightness and greater blue saturation, but less green saturation. Age differences influencing the color and structure of the cuticle were also observed: older males had more blue and green saturation and had more intact wax coverage than did younger males. Although multilayer reflection should be responsible for the iridescent color of males, our results suggest that wax coverage plays an important role in the color tuning of the male cuticle. This may have a considerable signal function, indicating the males' viability to competing males or to females.
雄性第二性征，如颜色图案，通常在宏观水平上进行研究。然而，微观和纳米尺度的形态学研究可能揭示出负责特定颜色的功能特征，从而提供更多信息，例如雄性性征的条件依赖性。本文的目的是研究两种同属蜻蜓雄性的表皮颜色及其结构，并揭示可能随年龄变化的颜色变化。根据分光光度计的测量结果，C. splendens 雄性的腹部比 C. virgo 雄性更蓝，蓝色饱和度更高，而 C. virgo 雄性则更绿，绿色饱和度更高。尽管这两个物种在结构层数和层间距上有所不同，但似乎覆盖外表皮的蜡晶体的完整性通常是与雄性表皮颜色参数相关的形态特征。使用氯仿去除蜡质也证实了结晶蜡覆盖对表皮颜色的影响：处理后，色调更蓝，表皮更亮，蓝色饱和度更高，但绿色饱和度更低。还观察到影响表皮颜色和结构的年龄差异：年龄较大的雄性比年龄较小的雄性具有更高的蓝色和绿色饱和度，并且具有更完整的蜡质覆盖。尽管多层反射应该是雄性彩虹色的原因，但我们的结果表明，蜡质覆盖在雄性表皮的颜色调谐中起着重要作用。这可能具有相当大的信号功能，表明雄性对竞争雄性或雌性的生存能力。
