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a period of rest in the development of animals, characterized by a sharp decline in metabolism and a halt in formative processes. Sometimes the concept of diapause is extended to other organisms.
During diapause the organism is more resistant to unfavorable external conditions. For example, insects become resistant to insecticides. In the temperate and high latitudes the onset of diapause in many animals is determined by the length of daylight. The termination of diapause is connected with changes in the organism, which may be caused by the prolonged action of low winter temperatures. Thus, diapause ensures the animal’s ability to withstand below-freezing temperatures and hibernation. In arid subtropical and tropical climates, summer diapause, or estivation, occurs (for example, in the pink bollworm and the tomato fruitworm).
In each biological species diapause is timed to a certain phase in the life cycle. Embryonic diapause is the period of rest in the egg stage between fertilization and mitosis or toward the end of mitosis. This type of diapause occurs in rotifers, lower crustaceans, grasshoppers, Chinese silkworms, and in a number of mammals belonging to seven orders (for example, rodents and predators, including sable and mink). Larval diapause occurs, for example, in the black-veined white butterfly, which hibernates in trees during the caterpillar stage. Pupal diapause is observed among large white cabbage butterflies and cabbage moths, which hibernate in trees and in the soil during the pupal stage. Imaginal diapause occurs in such insects as mosquitoes and leaf beetles (Colorado beetles). In imaginal diapause the animal may retain its mobility, but the process of sexual maturation ceases.
V. A. SVESHNIKOV