1 Vision Group, Department of Biology, Lund University , Sölvegatan 35, 22362 Lund , Sweden.
2 Adolphe Merkle Institute, University of Fribourg , Chemin des Verdiers 4, CH-1700 Fribourg , Switzerland.
J R Soc Interface. 2019 Apr 26;16(153):20180785. doi: 10.1098/rsif.2018.0785.
Animal colours commonly act as signals for mates or predators. In many damselfly species, both sexes go through a developmental colour change as adults, and females often show colour polymorphism, which may have a function in mate choice, avoidance of mating harassment and camouflage. In the blue-tailed damselfly, Ischnura elegans, young males are bright green and turn blue as they reach maturity. Females are red ( rufescens) or violet ( violacea) as immatures and, when mature, either mimic the blue colour of the males ( androchrome), or acquire an inconspicuous olive-green ( infuscans) or olive-brown ( obsoleta). The genetic basis of these differences is still unknown. Here, we quantify the colour development of all morphs of I. elegans and investigate colour formation by combining anatomical data and reflectance spectra with optical finite-difference time-domain simulations. While the coloration primarily arises from a disordered assembly of nanospheres in the epidermis, morph-dependent changes result from adjustments in the composition of pterin pigments within the nanospheres, and from associated shifts in optical density. Other pigments fine-tune hue and brilliance by absorbing stray light. These mechanisms produce an impressive palette of colours and offer guidance for genetic studies on the evolution of colour polymorphism and visual communication.
动物的颜色通常作为配偶或捕食者的信号。在许多蜻蜓物种中，雌雄两性在成年后都会经历发育颜色变化，而雌性通常表现出颜色多态性，这可能在配偶选择、避免交配骚扰和伪装方面具有功能。在蓝尾蜻蜓，Ischnura elegans 中，年轻的雄性是鲜艳的绿色，当它们成熟时变成蓝色。雌性在不成熟时是红色（rufescens）或紫色（violacea），成熟时要么模仿雄性的蓝色（androchrome），要么获得不显眼的橄榄绿（infuscans）或橄榄棕色（obsoleta）。这些差异的遗传基础尚不清楚。在这里，我们量化了 I. elegans 所有形态的颜色发育，并通过将解剖学数据与反射光谱与光学有限差分时域模拟相结合来研究颜色形成。虽然颜色主要来自于表皮中纳米球的无序组装，但形态依赖性变化是由于纳米球内蝶呤色素的组成调整以及相关的光密度变化所致。其他色素通过吸收杂散光来微调色调和亮度。这些机制产生了令人印象深刻的调色板，并为关于颜色多态性和视觉通讯进化的遗传研究提供了指导。
