From Big Medical Encyclopedia

DEFENSORS at animals — the eurysynusic biological devices in fauna serving for protection against predators, parasites, action of adverse environmental factors, mechanical influences, etc.; are observed practically in all groups of fauna.

Distinguish three main types 3. item: morphological, physiological and ethological. To morfol. 3. items carry all types of protective coloration, an originality of a shape of a body of animals, and also bodies of passive and active protection. At some types of land arthropods and vertebrate animals the body is painted under color of objects of the habitat or has the form reminding various objects from a surrounding situation, napr, knots, leaves (mimicry). A protective role is played by also dense armor dressing all body of an animal (e.g., at mollusks, turtles, etc.), the thorns or needles developing on an armor or on other parts of a body (needles of sea hedgehogs, fin beams of some species of fish, horns of hoofed animals, etc.), feathers, indumentum, scales, a fatty layer of skin. The contrast and bright color of animals (in particular, venomous snakes, fishes, etc.) as if warning other animals has protective and adaptive value.

To fiziol. 3. items refer the poisonous, frightening-off or masking properties of a lymph, blood, various glands (poisonous glands of peditsellyariya of sea hedgehogs, glands of a back fin Trachinus draco, gland of a sting of many Hymenoptera, etc.). Quite often protective value is gained by the glands which are not connected with any pricking device, but emitting badly the smelling substances, napr, glands of many bugs, bugs, ground beetles, an amer. skunks, etc. There are insects (e.g., ladybugs) at whom a protective role is played by the blood emitted in places of a joint of legs with a body.

Ethological 3. items are expressed at some animals in features of behavior, in elaboration of the so-called movements of threat: the skunk before the use of the protective glands preduprezhdayushche raises a tail, some lizards inflate the throat bags increasing the sizes of an animal. Defense reactions — flight from enemies, hiding in shelters (holes, nests, sinks), concealment, imitation of death (some insects) or wounds (the bird who are taking away the enemy from a nest), discarding of a tail (lizard), etc. belong to features of behavior of animals. Defense reactions can have also active character — attack. E.g., being protected, venomous snakes can put a poisonous sting; at careless handling even domestic animals can bite. To 3. items against unfavorable conditions of the environment refer migration of animals, an instinct of construction of nests and shelters, storage of forages etc. 3. items developed in the course of evolution and are useful to an organism only in the conditions of Wednesday, in a cut he lives. See also Adaptation , Adaptation .

V. A. Dogel.