Mäthger Lydia M, Hanlon Roger T
Marine Resources Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, 02543 MA, USA.
Cell Tissue Res. 2007 Jul;329(1):179-86. doi: 10.1007/s00441-007-0384-8. Epub 2007 Apr 5.
Nature's best-known example of colorful, changeable, and diverse skin patterning is found in cephalopods. Color and pattern changes in squid skin are mediated by the action of thousands of pigmented chromatophore organs in combination with subjacent light-reflecting iridophore cells. Chromatophores (brown, red, yellow pigment) are innervated directly by the brain and can quickly expand and retract over underlying iridophore cells (red, orange, yellow, green, blue iridescence). Here, we present the first spectral account of the colors that are produced by the interaction between chromatophores and iridophores in squid (Loligo pealeii). Using a spectrometer, we have acquired highly focused reflectance measurements of chromatophores, iridophores, and the quality and quantity of light reflected when both interact. Results indicate that the light reflected from iridophores can be filtered by the chromatophores, enhancing their appearance. We have also measured polarization aspects of iridophores and chromatophores and show that, whereas structurally reflecting iridophores polarize light at certain angles, pigmentary chromatophores do not. We have further measured the reflectance change that iridophores undergo during physiological activity, from "off" to various degrees of "on", revealing specifically the way that colors shift from the longer end (infra-red and red) to the shorter (blue) end of the spectrum. By demonstrating that three color classes of pigments, combined with a single type of reflective cell, produce colors that envelop the whole of the visible spectrum, this study provides an insight into the optical mechanisms employed by the elaborate skin of cephalopods to give the extreme diversity that enables their dynamic camouflage and signaling.
自然界中色彩丰富、多变且多样的皮肤图案最著名的例子见于头足类动物。鱿鱼皮肤的颜色和图案变化是由数千个色素性色素细胞器官与下方的反光虹彩细胞共同作用介导的。色素细胞（棕色、红色、黄色色素）直接由大脑支配，能在下方的虹彩细胞（红色、橙色、黄色、绿色、蓝色虹彩）上迅速扩张和收缩。在此，我们首次对鱿鱼（佩氏枪乌贼）色素细胞和虹彩细胞相互作用产生的颜色进行了光谱分析。我们使用光谱仪，获取了色素细胞、虹彩细胞以及两者相互作用时反射光的质量和数量的高度聚焦反射率测量值。结果表明，虹彩细胞反射的光可被色素细胞过滤，从而增强其外观。我们还测量了虹彩细胞和色素细胞的偏振特性，结果显示，虽然结构反射性虹彩细胞在特定角度使光偏振，但色素性色素细胞则不会。我们进一步测量了虹彩细胞在从“关闭”到不同程度“开启”的生理活动过程中所经历的反射率变化，具体揭示了颜色从光谱较长端（红外和红色）向较短端（蓝色）转变的方式。通过证明三类色素与单一类型的反射细胞相结合能产生涵盖整个可见光谱的颜色，本研究深入了解了头足类动物精致皮肤所采用的光学机制，正是这些机制赋予了它们极端的多样性，使其能够实现动态伪装和信号传递。
