SNAKES

From Big Medical Encyclopedia

SNAKES (Serpentes) — suborder of vertebrate animals, group of scaly (Squamata), class of reptiles, or reptiles (Reptilia); are characterized by the extended trunk, lack of extremities, an originality of a structure of the oral device adapted for swallowing a large catch.

Fig. 1. Diagrammatic representation of yadoprovodyashchy tooth of a gyurza: and — a lateral view; — an anterior aspect, in — a slit; 1 — inlet opening of the yadoprovodyashchy channel; 2 — the yadoprovodyashchy channel; 3 — outlet opening of the yadoprovodyashchy channel.
Fig. 2. An open mouth of a gyurza before a sting.
Fig. 3. The diagrammatic representation of an arrangement of yadoprovodyashchy teeth (1) and poisonous glands (2) at various snakes: and — gyurza — cobras, in — a steppe viper — a shchitomordnik, d — efa.
Some species of the snakes living in the USSR: 1. Viper ordinary. 2. Viper steppe. 3. Viper Caucasian. 4. Shchitomordnik east. 5. Medyanka ordinary. 6. Zheltobryukhy runner. 7. Multi-colored runner. 8. Gyurza. 9. Viper of Asia Minor. 10. Eph sandy. 11. East udavchik. 12. Slepozmeyka. 13. Sandy udavchik. 14. Caucasian cat's snake. 15. Arrow snake. 16. Cobra Central Asian. 17. Ordinary. 18. Water. Black circles designated venomous snakes.

It is known apprx. 2500 types 3., combined in 13 families. Vast majority 3. treats 7 families; slepun, lozhnonogy, or boas, uzhovy, adder, gadyukovy, yamkogolovy and sea serpents (tsvetn. fig.). Four last families usually combine under the general name «venomous snakes» which are characterized by existence in the forefront of an upper jaw of so-called poisonous teeth — yadoprovodyashchy teeth (fig. 1 and 2) which are reported channels with poisonous glands. Behind the operating pair of poisonous teeth several teeth substitutes are located usually. Glands are located in temporal area (fig. 3) and represent a modified part of salivary verkhnegubny glands. At some types they stretch under skin far behind the head.

This. Typhlopidae — the small snakes leading the digging life; eyes — in embryo. The typical representative — the slepozmeyka living in the territory of the USSR in Transcaucasia and Central Asia.

This. Boidae is the large snakes reaching in length of 10 and more meters. There are no poisonous teeth, production destroy squeezing or blow of the head. The majority of types lives in the tropical countries of Asia, Africa and America.

In the USSR in the Caucasus and in Central Asia meet sandy, east and other types of udavchik, the sizes to-rogo usually do not exceed 1 m.

This. Colubridae — the most numerous family (more than one thousand types). The typical representatives meeting in the territory of the USSR — ordinary, water, a medyanka, several types of poloz, and also an arrow snake, a cat's snake and others, meeting in the Caucasus and Central Asia.

This. Elapidae — the most poisonous types 3.: cobra, adder, bungar, etc. The cobra, or a cobra, meets in yuzh. parts of Central Asia.

This. Gadyukovye combines also poisonous 3. Poisonous teeth 3. this family are characterized by existence of the probodenny channel (at adders — only a groove). Here 10 childbirth including 60 types 3 enter., widespread in Africa, Asia and Europe. The central family of this family — the real vipers (Vipera) — contains 13 types, including 6 types — in fauna of the USSR: an ordinary viper (V. berus) extended in sowing. and average zones of the USSR, up to the Far East and Sakhalin; steppe viper (V. ursini) widespread in a steppe zone of the European part of the USSR, the Caucasus, Kazakhstan and Central Asia; the Caucasian viper (V. kaznakowi) living on West Caucasus and in Transcaucasia; a big-nosed viper (V. ammodytes) living in the west of Georgia; a viper (V. xanthina) of Asia Minor extended on Yu. Armenia and in Nakhchivan the ASSR; a gyurz (V. lebetina), living in east half of the Caucasus and yuzh. districts of Central Asia. The family of E. carinatus (Echis) includes only two look, one of which — sandy E. carinatus, extended to territories of the USSR in deserts and semi-deserts of Central Asia.

This. Yamkogolovy snakes (Crotalidae) it is close to gadyukovy and is considered sometimes as a subfamily of the last. Includes 6 childbirth (apprx. 120 types) extended in the tropical and moderated zones of Asia and America. Between nostrils and an eye there is a deep pole (from here the name) representing special thermoreceptor body with the help to-rogo 3. catch an invisible heat and define location of production at distance of tens of centimeters. Within the USSR two of 13 types of a sort of shchitomordnik (Ancistrodon) meet. The ordinary shchitomordnik (A. halys) is extended to Yu.-V. of Azerbaijan, the Lower Volga, in Kazakhstan, Central Asia and to Yu. Sibiri. East shchitomordnik (A. blomhoffi) is widespread in Japan, Korea, sowing. China and in the Far East. On the American continent rattlesnakes, or gremuchnik (childbirth of Crotalus and Sistrurus), and the largest of yamkogolovy snakes — a bushmeyster (Lachesis mutus) are found.

This. Sea serpents (Hydrophidae) includes close to aspidovy the forms living in tropical waters. All types are poisonous, eat fish. The horse-mackerel is most known veslokhvosty (Pelamydrus platyrus).

In addition to poisonous 3., which poison is life-threatening the person (see. Snake poison ), real danger is constituted by also some 3. from this. uzhovy, possessing the increased back and maxillary smooth or furrowed teeth which are in depth of a mouth. Are most known in this respect African bumslang (Dispholidus typus) and a wood snake (Thelotornis kirtlandi) which stings are often deadly to victims. From the types of this family which are found in the USSR, constitutes potential danger to the person Far East tiger (Rhabdophis tigrinus).

Length of a body 3. together with a tail from 10 cm to 10 m and more. The body is covered with horn scales. Eyelids are not mobile, spliced with each other, transparent and cover eyes outside; separate during a molt together with an old corneous layer of skin. The majority of bones of a skull connect to a cranium movably by means of strongly extensible sheaves that is adaptation to swallowing entirely a large catch. Numerous teeth are well developed and sit on maxillary, palatal, alate, tooth, and sometimes and on intermaxillary bones. The rachis is very flexible and consists of a large number in a special way of the vertebrae which are jointed with each other. All truncal vertebrae are supplied with mobile edges which rest against the belly guards set in motion by hypodermic muscles that promotes an animal during the crawling. At the majority 3. only one (right) lung is developed. In total 3. the predators eating only live production. Small types eat worms, mollusks, insects, spiders and other arthropods, large — mainly vertebrata: fish, Amphibia, lizards, other snakes, birds and small mammals. Production is eaten alive, previously is killed with poison, squeezed by rings of a body or destroyed by blow of the head (large nontoxic snakes).

3., as well as all reptiles, are poikilothermic animals (see), are active at air temperatures from +20 ° to +40 °, Depending on a look. Distribution 3. it is connected with ambient temperature and sharply decreases in the direction from the South by the North. So, in Central Asia lives apprx. 50 Types

3., in the North Caucasus — 28, in Central Europe — 15, Arctic Circle has only 2 look. With approach of winter cold weather 3. fall in hibernatation (see), duration the cut depends on cold resistance of a look. Under favorable conditions 3. can not fall into hibernatation, and in tropical zones at 3. there is no accurately expressed seasonality in change of the periods of activity and rest at all. Majority 3. winter in holes of rodents, cracks in the soil, caves etc.

Fertilization at 3. internal. Majority 3. lays eggs, some types — viviparous.

In deserts and steppes, where number 3. it is big, they bring considerable benefit, destroying harmful insects, mollusks, rodents. In some countries (especially in hot climate) 3. do serious harm to the person. E.g., in the countries of South America and Southeast Asia annually from stings poisonous 3. thousands of people die. Water ears are eaten in a large number of whitebaits of fishes and can cause serious damage to fishery, especially in districts of fish farming.

Poison of many 3. forms a basis for preparation of a row to lay down. drugs (see. Snake poison, drugs ). For receiving poison 3. special nurseries of snakes are organized.

See also .


Bibliography: Bannikov A. G., etc. Determinant of amphibiouses and reptiles of fauna of the USSR, M., 1977; Barkagan 3. Page and Perfilyev P. P. Venomous snakes and their poisons, Barnaul, 1967, bibliogr.; Valtseva. A. Pathophysiological features of effect of poisons of the snakes living in the territory of the USSR and some questions of experimental therapy, M., 1969, bibliogr.; P and at l of e of Sunday to and y S. V. Poisonous animals, Toxicology of invertebrates, L., 1975, bibliogr.; M. N. sultans. Stings of poisonous animals, M., 1963, bibliogr.; Talyzin F. F. Poisonous animal sushi and seas, M., 1970, bibliogr.; Poisonous animals of Central Asia and their poisons, under the editorship of G. S. Sultanov, Tashkent, 1970.

I. S. Darevsky.

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