Quantifying colour patterns on the black carapace of the fiddler crab Uca capricornis

Fiddler crabs are often spectacularly coloured and capable of dramatic colour changes. While the adaptive significance of variation resulting from short- or long-term colour changes is generally well known, the phenotypic diversity in colour pattern between individuals is often neglected. To fully understand the development and function of colour pattern variation, it is necessary to first describe its morphological basis and the naturally occurring diversity. - NB Colour pattern refers to the configuration of any coloured areas on the black carapace, regardless of their spectral composition. During this experiment 276 fiddler crabs of the species Uca capricornis were photographed - 117 females and 159 males. Using these pictures and a host of software programs, images were constructed that illustrate the probable colour patterns of various groups of crabs, including males and females in general, and males and females with various size classes; 18mm (no photographed females were >18mm). These images are the equivalent of an average crab's colour pattern. To more clearly illustrate the variation in colour pattern between the groups, similar images were constructed using the standard deviation of crabs coloured at each coordinate (1mm x 1mm square).招潮蟹（Fiddler crab）通常体色艳丽，且可发生显著的体色变化。尽管学界已普遍明确短期或长期体色变化所引发的变异的适应性意义，但个体间体色模式的表型多样性却常被忽视。若要全面解析体色模式变异的发育机制与功能，首先需阐明其形态学基础及自然存在的多样性。 注：本研究中体色模式（colour pattern）指黑色背甲上所有着色区域的排布形式，不考虑其光谱组成。 本实验共拍摄了276只摩羯座招潮蟹（Uca capricornis）个体，其中雌性117只，雄性159只。研究人员借助多款软件程序，基于这些照片构建了可展示不同类群招潮蟹典型体色模式的图像，涵盖雌雄整体类群，以及不同体长等级的雌雄个体；本次拍摄的雌性个体体长均不超过18mm（无体长>18mm的雌性样本）。 此类图像代表了单只招潮蟹的平均体色模式。为更清晰地展示不同类群间的体色模式差异，研究人员还基于每个1mm×1mm方形坐标处的着色标准差，构建了同类可视化图像。