Skin Colors and Patterns in Fish

Moet Hennessy-Louis Vuitton (LVMH)Sciencefor Art Prize Genesis of Forms: Part 11-Biology and Biomimetism Created in 1988, the Moet Hennessy-Louis Vuitton (LVMH} ScienceforArt Prize annually rewards artists and scientific researchers from all over the worldfor thepotential impad of their discovm’eson artistic or aesthetic creation. The 1996prize was awarded for workfalling under the theme “Genesisof Forms:Part I-Biology and Biomimetism. ” In 1997 theprize will be awardedfor “Genesis ofForms: Part 11-Mathematics, Physical and Earth Sciences.” Theprizes consist of twofirst prizes (an Art Prize and a SciencePrize} and the Vinci of Excellencefor scientific work of the highest international level (Lhesescientists reached thefinal stage of the selectionprocess). See Leonardo 30, No. 3% 183-186, and Leonardo 30, No. 4, 273-298, forfurther information about the LVMH Sciencefor Art Prize. SKIN COLORSAND PATTERNS IN FISH Ryozo Fujii, Department of Biomolecular Science, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274,Japan. E-mail: . The work reported in this Abstract was awarded the 1996 LVMH Vinci of Excellence Prize. We appreciate the beautiful colors and patterns displayed by many animal species . Among them, teleostean fishes constitute an extraordinarily wonderful group; we can enjoy, in addition to their “static”colors and patterns, spectacular changes to them. Such integumentary colors are dependent on the presence of pigment cells in the skin, namely, the chromatophores [11. These include the melanophores (black or brown), xanthophores (ocher or yellow ), erythrophores (red),leucophores (whitish), and the iridophores (metallic or iridescent). (I have been working for a long time to put the classification of chromatophores to rights, and my system is now widely accepted [2]). In some species of fish, we recently discovered blue chromatophores, naming them “cyanophores” [3]. Thus, six kinds of chromatophores are now known in poikilothermic vertebrates. The colors in these fish are generated by the absorption, reflection and/or the scattering of light of certain wavelengths by the pigment and the microstructures inside the cells. Usually containing a single kind of pigmentary material, each chromatophore is a small entity. When differently colored chromatophoresare distributed in the skin, the resulting color looks like a mixture of different colors. By making good use of the divisionisticeffects that chromatophores allow, the fish can exhibit a number of intermediate hues almost at will [4]. In common dendritic chromatophores , the aggregation of pigmentary organelles into the cell body, or their dispersion into the cellular processes, results in the fading or the increased coloring of the skin, respectively [5]. Containing stacks of thin, flat guanine crystals, by contrast, most iridophores are non-dendritic. By means of multilayer thin-film interference phenomenon occurring in the stacks, the cells can reflect light efficiently.Among these cells, the motile iridophores possessed by many coral-reef fish-and by many beautiful aquarium fishes such as the neon tetra-are especially interesting . We found that they reflect light within limited spectral ranges through interference phenomena of the nonideal type [6]. Very bright, fluorescentFig . 1. Ryozo Fujii. Diagram showingthe systemfor control of motile activitiesof common chromatophoresin teleosts. (ACh= acetylcholine;ACh-r =ACh receptor;AS-r= adenosine receptor;ATP = adenosinetriphosphate;Cap+= calciumions; CAMP= cyclicadenosine monophosphate;cGMP = cyclic guanosinemonophosphate;Epi = epinephrine;ET = endothelin;ET-r= endothelinreceptor;Glu = glutamate; Glu-r= glutamate receptor;IPsD#= inositol triphosphate;MCH = melanin-concentrating hormone;MCH-r= MCH receptor; MIH =MSH-releikeinhibitinghormone;MSH = melanophore-stimulating hormone;MSHr = MSH receptor;MT =melatonin;MT-r =melatoninreceptor;NANC fiber = non-adrenergic , non-cholinergicnerve fiber; NE = norepinephrine;NO = nitricoxide; a-r = a-adrenergicreceptor;p-r = Padrenergicreceptor.) Putative NANC fiber Pinealbody Endothelialcell 0 1998EAST LEONARDO, Vol. 31, No. 1, pp. 4145,1998 41 like hues are thus realized. In addition, in response to certain nervous or hormonal signals, the spacing between adjacent platelets changes concurrently, resulting in a shift of the spectral reflectance peak. In other words, continuous changes of hue-such as violet to yellow via blue and green-can take place 171. The motile activitiesof chromatophores (Fig. 1)are dependent on the intracellular presence of motor-proteins -namely, tubulin, dynein and kinesin-and are regulated by the endocrine and/or the nervous systems [8].We have clarified that the rapid aggregation of pigment granules, the chromatosomes, is aroused by the sympathetic division of the autonomic nervous...