Meaning of Chromatophore
Chromatophores, or chromatocytes, are cells that contain pigment molecules and have the ability to reflect light. These cells are found in various groups of animals, such as fish, crustaceans, cephalopods, amphibians, and reptiles (in birds and mammals the cells with pigmentation are the melanocytes).
During the embryonic process, chromatophores are generated in the neural crest, subsequently being responsible for the coloration of the animal’s skin and eyes.
Chromatophores are grouped according to the pigments they contain, defining their dominant color.
Xanthophores are chromatophores filled with yellow pigments, found in many animals such as the yellow corn snake (Pantherophis obsoletus quadrivittata) and the golden poison frog (Phyllobates terribilis) in which the yellow color serves as a warning to potential predators (color aphasic), as it is one of the most poisonous vertebrates on the planet.
There are non-venomous animals that develop striking colors similar to those that are genuinely dangerous through so-called Batesian mimicry. This is a predator avoidance strategy employed by many animals, such as the false coral snake.
Chromatophores with red pigments are known as erythrophores and are found in many animals, such as the red Humboldt squid (Dosidicus gigas), in salamanders, snakes, fish, and frogs.
Cyanophores are blue cells and, like erythrophores, are often associated with apematic (alert) features.
The highly venomous blue-ringed octopus (Hapalochlaena sp.) has cyanophores in circular portions (rings) throughout the body that glow blue when these animals are threatened. There are also frogs, eels and blue fish.
Another subgroup of chromatophores are the leukophores, cells that have purine crystals that reduce light diffraction that gives white or silver color to many species of fish.
Melanophores have brown or black pigments and are present in groups of reptiles (such as snakes in the genus Pseudechis) and many species of fish.
Finally, iridophores are reflective or iridescent cells that provide the ability to camouflage, observed in different groups of animals.
The chameleon, an animal belonging to the family Chamaeleonidae, is a classic example of an animal capable of camouflage. They have a large number of iridophores in the second superficial layer of the skin, which are made up of nanocrystals of guanine, which reflect and absorb light at specific wavelengths.
When the outermost layer of the skin is excited, the distance between it and the iridophores increases, allowing the skin to reflect longer wavelengths, such as yellow, orange, and red.
In a relaxed state, the skin reflects the shorter wavelengths (blue and green), which are the common colors of chameleons. Zebrafish and several species of squid are also endowed with iridophores, which allow them to manipulate the light spectrum and reflect many different colors.
Another physiological process that allows the change of color in animals is the translocation of pigments.
In this case, the vacuoles containing the pigments move within the cytoplasm of the chromatophores. When they are dispersed through the cytosol, they give the color associated with their characteristic pigment, however in some circumstances they can be concentrated only in the central region of the chromatophore, giving the impression that the animal’s skin is lighter or whitish.
This process is observed in fish, amphibians and reptiles, occurring as a consequence of hormonal or neuronal stimulation. In studies with fish, it has also been observed that environmental factors (such as pH and temperature) can cause this color change.