Chameleons are a type of lizards that make up the family Chamaeleonidae. There are about 200 species, all of them native to Europe, Africa and Asia. It can also be found as an introduced species in Hawaii and some regions of North America.
Although they are very famous for change color, only some species can do it. And although it is also often believed that they do it to camouflagemost of the time they do to regulate their body temperature and communicate with other chameleons.
In addition to changing color, these reptiles have other characteristics that make them unique. For example, your zygodactyl feeta type of finger arrangement present only in chameleons and some species of birds, such as parrots, cuckoos or some species of owls, with two pairs of opposing fingers, two forward and two backward.
Also characteristic is the quickly extensible tonguethe presence of horns and crests on the body and snout, and the pair of eyes with independent movement. Most species also have prehensile tail.
Why do they change color?
Chameleon species that can change color have layers of cells in their skin that contain pigments of various colors, including red, blue, orange, green, black, yellow or purple.
The color change has camouflage functions, but many patterns and colors use them in response to social cues and environmental conditions. However, depending on the natural habitat in which they live, each species may use one function relatively more than another.
Color changes in chameleons have an important social function. For example, it serves to show intentions to other chameleons. Chameleons tend to show brighter colors if they have aggressive intentions, while darker colors show an attitude of surrender or submission.
In Madagascar and the humid forests of Africa there are species with fluorescent pigments which are also believed to have a social communication function.
The camouflage function can be highly specialized. For example, him Smith’s dwarf chameleon (Bradypodion taeniabronchum), a species endemic to South Africa, can change its camouflage not only to blend in with its surroundings, but also depending on whether it is attacked by a snake or a bird. This species is capable of taking on colors that each type of predator cannot see.
The thermoregulatory function can also show high specialization in some species. For example, him namaqua chameleon (Chamaeleo namaquensis) lives in desert and semi-desert areas of South Africa, Namibia and Angola. During cold mornings it turns almost black to absorb more solar radiation. During the hottest hours it turns a very light gray.
How do they make their skin change color?
Chameleons have two layers to their skin that control color and thermoregulation. In both appear highly specialized cells (chromatophores) that contain vacuoles filled with different pigments.
For a long time it was thought that chameleons changed color by dispersion of those pigmented vacuolessomewhat similar to what octopuses and squids do, but this mechanism is only a small part of what chameleons do.
The iridophores are a specific type of chromatophore that contains a guanine nanocrystal latticeand chameleons can alter the organization of this network to modulate light reflected and absorbed by your body.
The state of the nanocrystals is controlled by the nervous system, increasing and decreasing the distance between the nanocrystals. In the excited state, the distance between the nanocrystals increases and longer wavelengths are reflected, such as yellow, orange or red.
In a relaxed state, the nanocrystals are much closer together and reflect short wavelengths such as blue and green.
The color change mechanism in chameleons is a combination of both.. On the one hand, the pigment vacuoles intervene, and on the other, they control the light reflected by the body. For example, the combination of yellow pigments and reflected blue light in a relaxed state results in the green color common to many chameleons.