In this journal article written by Nicholas Roberts et al., they investigate the counter shading and camouflage techniques of several species of schooling fishes. The authors examine how the differentiating layers of cytoplasm, in addition to two different types of Guanine crystals, aid in refracting light. The density differences of the cytoplasm layers, and the refractive indexes of the two types of Guanine crystals create unique reflective properties that alter the travel and direction of light. Because of these light properties of the Guanine crystals and different cytoplasm layers, it causes the polarization of light at many different angles rather than just one. This skin composition of these fishes essentially makes a polarization-neutral surface that makes them hard to visualize from many different angles.
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