From Big Medical Encyclopedia

POIKILOTHERMIC ANIMALS (Greek poikilos motley, changeable + therme warmth) — animals, body temperature at to-rykh is changeable and in most cases depends on ambient temperature.

To the Item. all protozoa and backboneless animals, and from vertebrata — fishes, Amphibia and reptiles belong.

The name «hematocryal» animals which is often applied as a synonym of the term «poikilothermic animals» is incorrect since the majority of the Item. transfer fervescence to 30 — 40 ° and are active in warm season, and some inhabitants of the tropical and equatorial countries perish during the cooling lower than 30 — 25 °. For the Item., living in northern latitudes and in a zone of a temperate climate, seasonal jumps of body temperature are typical: transition from an active state in the spring and in the summer to catalepsy or hibernation (see. Hibernatation , Hibernation ) during the cooling to 0 °. The main distinction between poikilothermic animals and animals with constant body temperature (see. Gomoyotermny animals ) consists in different intensity of processes of metabolism, including heat generation. At rest at the Item. body temperature changes according to changes of ambient temperature, differing from it on 1 — 2 °. In a condition of activity body temperature at them considerably increases. At gomoyotermny animals body temperature practically does not depend on conditions of the environment and a degree of activity of an animal. This constancy is provided with functioning of mechanisms thermal controls (see). To the majority of types of the Item. such features of behavior and a way of life which allow to maintain body temperature at optimum level are inherent; activity, reproduction and development during certain seasons of year etc. concern to them the choice of places with an optimum microclimate.

From a year cycle of life of many Items. (e.g., mites) seasonal changes of their value as keepers and carriers of causative agents of diseases of the person and animals depend (a tick-borne encephalitis, plague, a tularemia, rickettsioses, malaria, a piroplasmosis). The virus of a tick-borne encephalitis which got to an organism of a tick from wildings in the summer remains in it in the period of long winter catalepsy, and can be transmitted again in the spring. Fleas, having got drunk blood of the rodents infected with plague keep it activators in holes and nests of the owners and can promote development of an epizooty in the spring.

See also Body temperature .

Bibliography: Kalabukhov N. I. Hibernation of animals, page 17, 246, Kharkiv, 1956; Naumov N. P. Zooecology, M., 1963, bibliogr.; Prosser A. and Brown F. Comparative zoophysiology, t. 1 — 2, M., 1967; With l it and A. D m. Ecological zoophysiology, page 168, M., 1971.

N. I. Kalabukhov.