Some information about colors of fish.
The colors of fish are due to the presence of pigment cells called chromatophores. Chromatophores come in two varieties: those that absorb light and those that reflect light. Some light-absorbing chromatophores that occur in fish are melanophores, erythophores, xanthophores, and cyanophores. Leucophores and iridophores are examples of light-reflecting chromatophores. Inside chromatophores are organelles called chromatosomes. The type of chromatosome found in a chromatophore determines the color of the pigment cell. For example, melanophores, which are black, contain melanosomes, ie. melanin (black) is the pigment in the chormatosomes of melanophores.
Scientists have identified two types of color changes in fish: physiological and morphological. Physiological color changes are due to the spreading out or aggregation of chromatosomes. When the chromatosomes are spread throughout the cell, the color is more pronounced to the naked eye. However, when the chromatosomes aggregate in the center of the cell, the color is muted or not visable. Morphological color changes, on the other hand, are due to a change in the number of chromatophores. So a fish that loses a number of melanophores will appear lighter, and a fish that gains melanophores will appear darker. Physiological color changes can become morphological color changes over time. For example, a fish that is kept in a tank with a dark background and dark rocks will become darker, initially because of movement of melanosomes in the already exisiting melanophores. However, if enough time goes buy, the fish will start to produce more melanophores and
then the color change is considered morphological.
The common phenomenon of black color fish turning orange, or young fish losing black markings as they grow is an example of a morphological color change. As the fish mature, they lose melanophores in a process called apoptosis. Apoptosis is directed cell death, or cellular suicide, and is an important phenomenon in many aspects of development. However, the exact molecular cues that tell a cell it's time to die are still very mysterious. In addition to apoptosis, fish that lose black coloration are also supressing the birth of new melanophores. The loss of melanophores reveals the other pigment cells present in the skin. The type and extent of color change a young fish will go through depends on their individual genetic makeup, and there is a lot of variation between individuals! Some fish even go through a second color change from the destruction of xanthophores (red pigment cells).
For flowerhorns to maintain black markings, a darker color background can be used to help maintain black markings.
Hope this information can help educate why some flowerhorns lose flower markings.
Mainly Genetics also.
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