Chameleons: camouflage virtuosos
But what kind of animal is it, with which most people are familiar only by hearsay, and not vividly, and about which three things are widely known: it can change the skin color, rotates the eyes in different directions, independently of one another, and shoots the tongue neatly?
The main answer to this question is this: no matter how surprised a human chameleon is, its quality is a consequence of a specialized lifestyle, and the overwhelming number of eight dozen species of chameleons lead a strictly woody life, in the extreme case, a shrub. Only a few permanently live in earthen holes or live among the fallen leaves on the ground. There are cases of finding chameleons even in ant nests, where they penetrate through the wide passages of insects.
Of the almost 200 species of chameleons known to modern science, the vast majority live in Madagascar and neighboring islets, as well as in neighboring Africa. One species is found in southern Spain, on a number of islands in the Mediterranean, in the Balkans, in Asia Minor and Syria; two species will meet in Arabia and one – in India and on the island of Sri Lanka. Some were deliberately or accidentally brought far from their native places, but adapted to a new life, for example, in Hawaii or Florida.
These creatures are diverse and their size. For example, the Tamele chameleon, the largest of the chameleons of Madagascar, reaches a length of 68 cm. However, another Madagascar has the same dimensions, the Parson’s chameleon. However, they are both surpassed by a colleague from the African continent – the Meller’s chameleon, growing to 76 cm or more. His menu of some insects is no longer comfortable, and he diversifies his diet with other lizards, frogs and small birds. But the Madagascar chameleons of the genus Brookesia are considered one of the smallest lizards: the total length of the Brookesia does not exceed 4.5 cm.
The ability of chameleons, characteristic of chameleons, to quickly change color and body pattern, from which the name “chameleon” originated, after a mythological creature changing its appearance, became widely known. The change in color of chameleons is due to the structural features of their integuments. In the outer, fibrous and deeper layer of the skin itself, chromatophores are enclosed – branched cells with grains of dark brown, reddish and yellow pigment inside them. With the reduction of chromatophore processes, the pigment grains are concentrated in the center of the cells, and then the skin looks whitish or yellow. When the dark pigment is concentrated in the fibrous layer of the skin, it becomes dark, almost black in color. The appearance of different shades is caused by a combination of pigments of both layers. Green hues additionally result from the refraction of rays in the surface layer, which contains many highly refracting light guanine crystals. As a result, the color can quickly change from whitish and orange, through yellow and green to purple, dark brown and black, and these changes can capture both the whole body and its individual parts and be accompanied by the appearance and disappearance of various kinds of stripes and spots. The described color changes occur under the influence of both external factors – temperature, light and humidity, and as a result of hunger, fear, thirst, irritation, etc.
As a rule, the coloring of chameleons harmonizes well with the surrounding background, hiding the animal from the eyes of numerous enemies. Yes, and traditionally it was believed that these lizards change the color of the body exclusively for mimicry under the surrounding leaves or grass, to protect against predators. However, in experiments with a variegated mountain chameleon from North Africa, zoologists have found that this is at least not quite true. They provoked the males to “duel” with each other in the natural conditions for them and measured the color saturation with the help of spectrometric equipment. Which allows to fix the radiation not only in the visible, but also in the ultraviolet part of the spectrum, because chameleons are able to “be painted” and in colors invisible to the human eye.
It turned out that the greatest variation in coloration colors was observed in species with the most pronounced social behavior — to communicate with other chameleons, and not in species that live in places with a large number of multi-colored objects (grass, tree trunks, leaves).
It is clear that the coloring of chameleons, which use the maximum number of colors, is more noticeable not only for their relatives, but also for predators, and this contradicts the adaptive theory of color change. However, the evolutionary press did not lead to the destruction of such “bright” species, since chameleons are able to change color in a few milliseconds, so that predators often do not have time to notice them.
Eyes and feet
The organs of vision of chameleons have a completely unusual structure. Their large round eyes are surrounded by a continuous, covered with scales ringed eyelids, in the center of which there is a small hole for the pupil. The rest of the eye is constantly hidden under the skin and is not visible from the outside. Eye movements of chameleons are completely independent of each other, and both can rotate freely.