Data from: Changeable camouflage: how well can flounder resemble the colour and spatial scale of substrates in their natural habitats?

Flounder change colour and pattern for camouflage. We used a spectrometer to measure reflectance spectra and a digital camera to capture body patterns of two flounder species camouflaged on four natural backgrounds of different spatial scale (sand, small gravel, large gravel and rocks). We quantified the degree of spectral match between flounder and background relative to the situation of perfect camouflage in which flounder and background were assumed to have identical spectral distribution. Computations were carried out for three biologically relevant observers: monochromatic squid, dichromatic crab and trichromatic guitarfish. Our computations present a new approach to analysing datasets with multiple spectra that have large variance. Furthermore, to investigate the spatial match between flounder and background, images of flounder patterns were analysed using a custom program originally developed to study cuttlefish camouflage. Our results show that all flounder and background spectra fall within the same colour gamut and that, in terms of different observer visual systems, flounder matched most substrates in luminance and colour contrast. Flounder matched the spatial scales of all substrates except for rocks. We discuss findings in terms of flounder biology; furthermore, we discuss our methodology in light of hyperspectral technologies that combine high-resolution spectral and spatial imaging.

比目鱼（Flounder）可通过改变体色与体表斑纹实现伪装。本研究使用分光光度计（spectrometer）测量反射光谱，并借助数码相机采集两种比目鱼的体表斑纹图像，这些比目鱼分别在四种不同空间尺度的自然背景——沙质基底、小砾石、大砾石与岩石——上完成伪装。我们以完美伪装情境（即比目鱼与背景的光谱分布完全一致）为参照基准，量化了比目鱼与背景间的光谱匹配程度。计算针对三种具有生物学意义的视觉观察者展开：单色视觉的乌贼、二色视觉的蟹类以及三色视觉的犁头鳐。本研究的计算方法为分析具有高方差的多光谱数据集提供了全新分析路径。此外，为探究比目鱼与背景的空间匹配度，我们使用一款最初用于研究乌贼伪装的定制程序，对比目鱼的斑纹图像进行了分析。研究结果显示，所有比目鱼与背景的光谱均处于同一色域范围内；且针对不同视觉观察者的视觉系统而言，比目鱼在多数基底上的亮度与色彩对比度均实现了匹配。除岩石基底外，比目鱼均能匹配其余所有基底的空间尺度。我们从比目鱼生物学视角对研究发现展开讨论，并结合融合高分辨率光谱与空间成像的高光谱技术，对本研究的方法论进行了阐述。