page_title: Fish coloration
section_title: Color change
hierarchical_section_title: Fish coloration / Evolutionary function / Color change
caption_attribution_description: English: Midas cichlid (Amphilophus citrinellus). A private zoo collection. Ukraine. Русский: Цихлозома лимонная. Аквариумная рыбка из семейства цихлид (Amphilophus citrinellus) Українська: Акваріумна рибка з сімейства цихлід (Amphilophus citrinellus). Приватна колекція. Україна.
context_page_description: Fish coloration, a subset of animal coloration, is extremely diverse. Fish across all taxa vary greatly in their coloration through special mechanisms, mainly pigment cells called chromatophores. Fish can have any colors of the visual spectrum on their skin, evolutionarily derived for many reasons. There are three factors to coloration, brightness, hue, and saturation. Fish coloration has three proposed functions: thermoregulation, intraspecific communication, and interspecific communication. Fishes' diverse coloration is possibly derivative of the fact that "fish most likely see colors very differently than humans".
context_section_description: Color change in fishes can be roughly divided into two categories: physiological color change and morphological color change. Physiological color change is considered to be more rapid and consist of motile chromatophore responses, while morphological color change consists of the density and morphology of chromatophores changing. Overall, morphological color changes are considered to be a "physiological phenomena involved in the balance between differentiation [of melanophores] and apoptosis of chromatophores" but are still being studied; that is to say it has to do with the synthesis of pigment. The genetic factors behind natural morph variants of color in fish are still mostly undiscovered. Some hormonal factors of morphological color change in fish include α-MSH, prolactin, estrogen, noradrenaline, MCH, and possibly melatonin. Some of these are also involved in physiological color change. In physiological color change, there is also neurohumoral regulation of chromatophores in fish. Additionally, there have been found to be "differences at the intracellular level where fish chromatophores show smaller, better coordinated, and higher speed of the pigment organelles" in comparison to color-changing frogs.
  An example of physiological color change is found in the black-spotted rockskipper (Entomacrodus striatus). They are known to change color rapidly using their chromatophores, which is thought to enhance their crypsis in the "high-contrast environment of the rock wall". Another example of physiological color change is in the body and the eyes of guppy juveniles and Nile tilapia. 
  An example of morphological color change is in the Midas cichlid (Amphilophus citrinellus), that has "normal" and "gold" polymorphisms. Most of these cichlids maintain a "normal" grayish color pattern from juvenile to adult. However some of these species undergo morphological color change over their lifetimes, growing to be a gold or white color pattern as an adult. Another example of a fish that undergo morphological color change is the Hyphessobrycon myrmex sp. nov.. Juveniles are pale yellow and females maintain that color as adults. Males undergo morphological color change and become red or orange
caption: Midas cichlid with the gold polymorphism.
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