Noriko Oshima* and Akiko Kasai
Department of Biomolecular Science, Faculty of Science, Toho University, Funabashi, Chiba 274-8510, Japan
*E-mail address: oshima@biomol.sci.toho-u.ac.jp
(Received April 4, 2002; Accepted July 9, 2002)
Keywords: Iridophores, Multilayered Thin-Film Interference, Norepinephrine, Skin Color, Zebrafish
Abstract. We examined the distribution of iridophores in the skin of the zebrafish and the effects of a neurotransmitter and hormones on the cells. In the skin of deep blue stripe areas, motile iridophores are distributed over the layer of melanophores, while in the dorsal skin, such cells underlie melanophores and xanthophores. These iridophores assume blue coloration in physiological saline probably through multilayered thin-film interference phenomenon of non-ideal type, and norepinephrine (NE) induces color change to yellow within 1-2 min. The action of NE is mediated through a-adrenoceptors on the iridophore membrane. MCH (melanin concentrating hormone) and MSH (melanophore stimulating hormone) have no effect on the cells. Iridophores manifesting whitish color exist densely in the skin of white stripe regions, and these iridophores are immotile. Immotile iridophores of another type are compactly arranged beneath the melanophore layer in the skin corresponding to deep blue stripes. The role of the iridophores in the generation of skin color and its changes is discussed.