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The iridophores of some fishes including the neon tetra, Paracheirodon innesi, contain regular alternating layers of guanine and cytoplasm whose spacing changes in response to light, even in decapitated animals. As a result, the wavelength of light that is most strongly reflected also changes and the iridophore changes colour. These iridophores give the colour to the bright iridescent lateral stripe that includes the iris and runs laterally along the body. The iridophores themselves are located between the dermal collagen and the underlying muscle. The photosensitive site appears to be located within the cell itself, or very close to it. Using an immunofluorescence technique, we describe here the identification of an opsin-based visual pigment within the neon tetra iridophore.

Original publication




Journal article



Publication Date





83 - 84