The Beautiful Animal Skin
What really makes you to stare an animal for so long? Of course, the body stature and the colour. But you never imagined the complexity inside the mechanisms of its colouration which varies with every species whether be it of vertebrate, reptiles or amphibians. The vertebrate skin is comprised of a thin outer stratified epithelial layer, the epidermis, derived from ectoderm and an inner, thicker layer, the dermis or true skin, which is of mesodermal origin and is made up of nerves, blood vessels, connective tissue, pigment, etc.
Skin Types An Coloration
The skin is modified in many ways. For example, the tough, protective scales of fishes, although appearing to be surface structures, are actually bony plates produced in the dermis. The scales of reptiles, however, are horny, keratinised plates of epidermal origin. In snakes the ventral scales form transverse bands which assist in locomotion. Snakes periodically shed their skins as they grow. For every living thing millions of instructions called genes and are used for its appearance including coat colour, growth and maintenance.It is well to discriminate between colour and coloration in animals. Colour refers more particularly to actual shades or tints, whether red, yellow, green, or the like, whereas, coloration is used to specify the arrangement of individual colours into patterns. The colour in animals, it is the basis from which may colour patterns be constructed and can be useful in the business of life. The principle of obliterate coloration is based largely upon the breaking up of the contour that renders an animal of uniform colour tone conspicuous. Man has taken the hint from nature in the last war, and developed the art of camouflage by painting his ships in bizarre patterns that effaced contour lines and thus, made them inconspicuous.Obliterative coloration, services an animal in concealing it from enemies that might injure or kill it. It is commonly termed as protective coloration. The inconspicuousness may result from a general resemblance to surroundings, as in the instances already cited, or it may apparently be special, resembling some particular object in the surroundings.The existence of special protective resemblance, however, is questioned by some naturalists, who are inclined to believe that the resemblance to some particular object is largely accidental and its actual utility is a special device which has not been proved, and at times when the colour or pattern proves advantageous, it is merely because of its general obliterative effect. Such, allegedly special resemblances are sometimes classed as mimicry. The examples of special resemblance are found in the stick caterpillars and the walking sticks which look like dried twigs, in various insects which resemble leaves or lichens or even bird-droppings, in leaf-edge caterpillars or the mirror-back caterpillars which reflect the colours around them. Protective colouring is also designated as signals and these may be either warning or recognition colours. Those animals which bear warning colours or use other warning devices have generally inedible or possess weapons which are dangerous or offensive to others. Thus, other animals seldom attack the skunk because in daylight, its striking black and white coat plainly advertises its undesirable qualities.Among insects some of the best examples of what have been regarded as warning colours are found. Many slow-flying, bright-coloured butterflies not only are suitable but frequently are nauseating as food, and their very conspicuousness thus, save them from being seized by birds and other insect-eating forms. So, too, such sting-bearing forms as bumblebees, honeybees, and many wasps flaunt gaily banded yellow and black coats about with impunity.The so-called recognition colours, commonly seen in gregarious animals, are believed by some naturalists to be useful identification marks by which members of a flock or herd can recognise their own kind, and to be particularly helpful as beacons to the young in following or finding their fleeter elders. The white tails of various deer, the cottontail of the rabbits, the white rump-patches of the prong-buck, the white feathers at the base of the meadow lark's tail, and the like, are often cited as examples.
More About Skin Colours
Certain animals exhibit what is sometimes called variable protective coloration, changing with the season. Thus, certain hares and various birds, such as the ptarmigan (a grouse) are white in winter but brown or grey in summer, thus, harmonising with their surroundings after the snow has disappeared. Some animals can change colour rapidly by varying the degree of dispersion or concentration of the pigmentary particles in special pigment cells (chematophores) in the skin.
Because so many birds, mammals, reptiles, and fishes as well as the invertebrates, insects, crustaceans, and mollusks, are more or less protectively coloured, the subject offers many interesting research problems to the ethologists. The student of the human form is spared this difficult phase of art simply because man's skin coloration is practically a monotone. There are, to be sure, delicate tints of colour, yellow, green, white, or red as the case may be, but no intricate lines of spots or stripes, no colour shading from dark to light, and vice versa, and no question of how to treat fur, feathers, or scales upon the body surface.
For many years under the influence of man like the great English naturalist, Charles Darwin, we assumed that the reason a tiger was more or less invisible against his background lay in the fact that it was the same colour as its background. It remained, however, for distinguished painter Abbott H. Thayer, himself a naturalist of parts, to clarify and amplify this statement by declaring that the big cat was made invisible because its maze of stripes and colour so broke up the concrete body form that it assumed the effect of the light and shade upon that background, a very different point, but one that we now recognize to be well taken. As a matter of fact, many species of the cat family are thus effectually screened from observation, not only by striped effects, but by elaborate patterns of spots as well. Leopards, jaguars, and numerous others are so protected.
One is amazed at the variety of ingenious designs thus employed. Certainly the rich, gleaming coat of the leopard or a jaguar is one of nature's most beautiful skin decoration, tremendously elaborate, the shape and size of the spots varying at many points and forming a pattern that is a most potent factor in concealing the fierce creature to an extraordinary degree.
Besides, concealing pattern in animals, there is also the device of cancelling the light and shade by darker or lighter body tones, though the actual colour remains practically the same over the entire animal. The lions and pumas are good examples of this type of concealment, the darkest shades being found along the back of the animals, with lighter tones on the side and still lighter on the belly. The result of this scheme is obvious, the darker colour being offset by the brighter light on the back, the belly in shadow relieved by the lighter tone of the fur.
Indeed, this type of shading exists even when the skin is covered with spots or bands. White is a fairly common colour among birds; black or the effect of black occurs quite frequently; red, yellow, blue, and green in every shade and design exist among these lovely feathered creatures. In reptiles we see again in many species most beautifully worked out schemes of colour, spots, and bands. Rattlesnakes, copperheads, pythons, boa constrictors are all thus subtly decorated, their coiled forms thus becoming essentially a part of their environment.
Skin Of Fishes
Fishes as well offer delightful and amazing examples of nature's concealment plan. This accomplished in a number of ways, by colour, bands, stripes, and spots, iridescence, actual skin projections, and the simulation of bits of seaweed and other objects.
In many species this is combined with the unusual power of actually changing their normal skin appearance by bringing forth or retiring brilliantly contrasting shades; the general effect of the marvellously constructed creature is thus entirely altered. The sargassum fishes, living in the weed of the same name, are unbelievably like their surroundings in colour, pattern, and even form, their grotesque body and fin construction greatly adding to the general effect. Sometimes, they assume fearful to decieve the enemy by making themselves very difficult to distinguish against their submarine backgrounds of coral rock and seaweed.
So down the long pathway of life we may wander with ever increasing interest and delight as we survey the manifestations of beauty and versatility of the coat colouration of different animal species. To see is to know, and to enable him to see accurately is to put into every mind, the greatest power of expression of nature.