Guppy Color System
From Guppy Wiki
What we see is not necessarily what we get when it comes to guppy colors. Examination under a microscope reveals that the color cells form a very fine system of dots, just like the dots on a TV screen or a computer monitor. This picture shows an area of guppy skin as seen under a microscope:
Fig. 1 Guppy color cell showing yellow and black color cells.
There are also light-reflecting iridophores. Seen from a distance, the yellow, white light-reflecting and black color cells appear to merge into grey.
Color cells are layered. Fig.2 by Dr. José René Meléndez Berríos, guppy breeder and surgeon, shows a transverse section through the peduncle of a blond red guppy.
Fig. 2 Cross-section of the guppy skin. Study by Dr. José René Meléndez Berríos.
You can see the layered arrangement of red and yellow color cells in the epidermis of the guppy’s skin. Color cells in the guppy are not two-dimensional. They exist in three-dimensions.
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The Four Classes of Color Cells
The layers contain four classes of color cells that combine to produce the thousands of colors of the guppy and other fish.
- Erythrophores or red color cells
- Xanthophores or yellow color cells
- Iridophores or light reflecting color cells
- Melanophores or black color cells
Fig. 3 Guppy Color System. See Bagnara and Hadley (1973) "Chromatophores and Color Change" for a detailed description of the color system used by fish, amphibians and reptiles.
The color cells are arranged in three basic layers (Fig. 3). The graphic shows the way light strikes and penetrates the three layers.
- The bottom Absorbing Layer absorbs all sunlight, preventing damage to internal organs from the sun’s rays. It also absorbs scattered light rays that are bouncing around in the layers of the skin.
- The middle Reflecting Layer scatters or refracts light. It reflects light from the body like tinfoil or white metal.
- The top Filtering Layer is made up of pigment color cells that selectively absorb different parts of the light spectrum. For example, the yellow color cells absorb all but the yellow part of the light spectrum. The yellow part of the light spectrum is reflected.
In the diagram, three rays of sunlight have been labelled 1, 2, and 3. Each of these rays penetrates the skin and strikes a color cell.
- The first ray immediately strikes a yellow color cell (xanthophore). All but the yellow part of the ray’s light spectrum is absorbed. The yellow light is reflected. You would see yellow on the skin of the guppy.
- The second ray strikes the reflecting platelet of an iridophore, a type of color cell that reflects and scatters light. The ray is reflected back up and passes through a red color cell. The red color cell acts like a filter, absorbing all but red light. You see metallic red on the guppy, such as coral red. If the ray had not struck a color cell on its way back up through the skin, the viewer would see such metallic colors as Japan Blue, silver or Micariff metallic white. See Figure 4 below.
- The third ray passes right through to the melanophores at the base of the skin, where it is absorbed and not reflected.
Examples of Reflected Colors
In the series of pictures below, you will see how the color light is subtly changed by the different color cells at different layers. The example is colors reflected off of iridophores and filtered by the pigment color cells.
Fig. 4 Microscope view of a guppy with a lot of silver iridophores. Notice that the yellow color cells above the iridophores filter the light, producing a gold color. The light is shining directly down from above. The light reflecting off the iridophores, and back through the yellow color cells gives this guppy its burnished gold look.
Fig. 5 Gold Metallic Guppy. Philip Shaddock
Fig. 6. Here is the skin in Fig. 4 again. Notice the dramatic difference. In this case, the light is not bouncing off the iridophores, but passing through them from below.
Iridophores come in three common colors: blue, white and silver. (See the Iridophores: Metallic and Platinum Colors article in the Notes section.) This is not the color of the iridophore, since iridophores are colorless. Rather it is the color of light selectively reflected by the iridophore. (There are also color interference colors, but they will be ignored at this time.)
Seen from a distance, the combination of the silver light reflecting iridophore and yellow pigment color cells (Fig. 4) looks like a gold metallic guppy (Fig. 5).
This sword has a platinum yellow look.
Fig. 7 The yellow color cells are probably sitting on top of white light-reflecting iridophores. Photo: Tomoko Young This is a simplified view of the guppy color system. It assumes a normal or wild-type arrangement of color cells. Mutations cause the color cells at each of the layers to increase or decrease in density, size and number, or be absent altogether. A Moscow guppy has a huge number of black color cells and relatively few in the other layers.
Mutations like albino in effect remove the effect of a complete class of color cells (Fig. 8).
Fig. 8 This albino Half-Black white guppy is missing the black component of the Guppy Color System.
Color Mixing
To some extent you can think of the Guppy Color System as a color mixing system, not unlike the way colors are mixed in the computer monitor. This brings us to the art of guppy breeding, based on the science of the Guppy Color System.
The computer monitor is capable of displaying millions of colors. But it uses only three primary colors to do this, mixing them to get the other colors. The color wheel can be pictured like this (Fig. 9).
Fig.9 The Guppy Color Wheel
The three triangles at the center of the wheel, red, yellow and blue, represent the three basic color cells in the guppy, the red, yellow and blue iridophore colors. Black is spread evenly among the three colors, varying the darkness or saturation of the color.
Like the tiny beams of light coming from the computer monitor, the light bouncing off the tiny color cells of the guppy mixes to create millions of colors. For example, the guppy color green is a result of the mixing of yellow pigment color and the reflected blue light from iridophores. If you look at the color wheel, you will see that green (marked no. 1) is the combination of yellow and blue.
Similarly a Purple Moscow has a mixture of red and blue-light reflecting color cells (see no. 2 on the wheel).
The third example is orange (marked 3 on the diagram), a mix of red and yellow.
Conclusion
This is a huge subject and I have only skimmed the surface. However it should give you a start on understanding guppy color better.
