Protective Adaptations

PROTECTIVE ADAPTATIONS, a biological phenomenon widely distributed in the animal kingdom. Protective adaptations serve animals for protection against persecution by predators, parasites, etc. Many types of protective adaptations are distinguished. Thus, first of all, in the external morphology of animals, a dense shell plays such a role (e.g., in mollusks, turtles, etc.); a further improvement of protective adaptations is the development on the shell or on other parts of the body of spines, needles, and similar sharp outgrowths (needles of sea urchins, fin rays of sticklebacks, horns of ungulates, etc.). In addition to spines, protective venom glands may form (glands of the pedicellariae of sea urchins, glands of the dorsal fin of Trachinus draco, glands of the sting of many Hymenoptera, etc.). Often, stink glands, not connected with any stinging apparatus, acquire a protective significance; such are the glands of many bugs, the anal glands of the American skunk, the glands of ground beetles, etc. There are insects in which the protective substance is not a secretion of special glands, but the blood of the insect (ladybugs), secreted at the joints of the legs with the body. Cephalopod mollusks possess a completely peculiar protective adaptation in the form of an ink sac, i.e., an anal gland, from which a substance is ejected that clouds the water and allows the animal to escape from an enemy. This is a transition to protective adaptations of camouflage and protective coloration. An example of camouflaging animals are some crabs, which carry a sponge masking the crab on their back with the help of their hind pair of legs. The mollusk Xenophora glues empty shells of other mollusks to its own shell, covering it in the form of a pile of debris, etc. In other animals, the body itself is colored to match the environment or even takes on a shape resembling various objects from the surrounding environment, for example, twigs, leaves, etc. (see Mimicry).

Finally, in some animals, protective adaptations are expressed in the peculiarities of the organism's behavior, in the development of so-called threat movements. Thus, a skunk, before using its protective glands, warningly raises its tail; some lizards inflate their throat sacs, which increase the volume of the animal; similar behavior of a turkey, etc., also belongs here; here, threatening sounds (hissing of a turkey, etc.) are added to the spreading of feathers. Often, one and the same organism possesses several types of protective adaptations. (See also Immunity.) V. Dogel.