Beauty and health of teeth 

A group of reptiles without limbs. General characteristics of the reptile class

Reptiles are very interesting and very unusual creatures. The general characteristics of these creatures are very detailed. Which is not surprising, because this class of chordates includes snakes, lizards, amphisbaenae, beakheads, crocodiles, and turtles. All of them have many distinctive features. Of course, it will not be possible to briefly tell about everything, but about the most interesting - completely.

A bit of history

Where do reptiles originate? A general characteristic always begins with information about it. It is logical, because it does not hurt anyone to know that the terrestrial animals belonging to this class are distant descendants of the dinosaurs that dominated the Mesozoic era for more than 160 million years. As you know, they died out about 66 million years ago. Modern reptiles can only be compared to the scattered remnants of that beautiful, mysterious ancient world.

It is also important to know that ancient reptiles are the ancestors of birds. It was they who gave rise to this group of animals, which is now actively flourishing. Scientists have long known that the adaptations that determined the evolution of birds were observed in their ancestors - representatives of special forms of reptiles. They were characterized by warm-bloodedness, a developed brain and an insulating body cover (feathers).

Cover

Now - a little more detail about the anatomical specifics inherent in such creatures as reptiles. A general characteristic states that they have features of both amphibians and higher ones. What about the outer cover? Due to thickening and subsequent keratinization, it forms scutes and scales. Such a cover protects the tissues and organs of the animal from the effects of external stimuli and from moisture loss.

And the scales help snakes to move around. Due to the presence of plates, animals repel themselves from uneven ground and move in one direction or another.

The integument of reptiles is different. In some creatures, the scales fit snugly together. For others, they go as if "overlapping". In some, they even transform into crests or spikes, due to which creatures are protected from predators.

But one of the most interesting integuments can be observed in the Moloch lizard (lat. Moloch horridus). It is also called the "prickly devil". Looking at the photo above, you can understand why. This small Australian desert lizard has a wide and flattened body covered with countless short curved horny spines of various sizes. Above the eyes and on the cushion-like outgrowth on the neck, they form something resembling horns. This golden brown lizard is able to change its color depending on the light, temperature and its physiological state.

But it is worth returning to the topic of cover. Does it interfere with the growth of reptiles? No, because periodically they shed their old skin. And in the process of molting, their growth occurs. And the new cover differs in elasticity and softness. It takes time to become cornified, and during this period these creatures hide because they are vulnerable without protection.

Skeleton structure

It is also important to mention it if we talk about what anatomical features reptiles have. The general characteristic is very interesting, because the total number of vertebrae can reach several hundred! An adult (lat. Eunectes murinus), for example, has about 435 of them! It's impressive. But if we exclude snakes, then the total number of vertebrae of other reptiles varies from 50 to 80.

But the structure is identical for all. And by the way, the division into departments is much more pronounced than in the case of amphibians. Five vertebral regions are distinctly distinguished: cervical, trunk, lumbar, sacral and caudal. The last of these contains the maximum number of notorious vertebrae. They have a very interesting structure: the closer to the tail, the smaller their size. The last vertebrae are completely similar in structure to tiny bones in the form of sticks.

However, in some groups of reptiles, the skeleton has a different structure. In snakes, for example, only the trunk and tail sections are clearly visible. There is no chest. And the vertebrae of the trunk section of the turtles completely grow together with the shield of the shell, which is why they lose their mobility.

Scull

Also, the general characteristics of reptiles can tell a lot about the structure of the skull of these creatures. Especially about the snake. Its structure has evolved depending on the methods of obtaining food and the nature of nutrition.

Amphibians, for example, have a short and wide skull with elongated jaws that form a very long snout. The structure of the mouth allows these creatures to capture small prey when it is attacked.

But in reptiles, the capture of prey is directly related to the pursuit of the victim. And the elongated snout here has significant advantages. In addition, it is precisely this shape of the jaws that allows you to tear off a piece from large prey. In crocodiles and turtles, by the way, the palatine processes form a secondary bony palate, which divides their oral cavity into lower and upper sections. Therefore, they can breathe only by exposing the end of the head with nostrils out of the water, because the choanae (internal nasal openings) are shifted back, closer to the larynx.


Muscular system

Her description also includes general characteristics of reptiles. The muscular system of these creatures is differentiated, represented by segmental muscles. A distinctive feature of these creatures is the intercostal muscles, which perform the most important functions in the implementation of breathing.

Of particular interest is the subcutaneous musculature. In some representatives, it is so highly developed that it allows creatures to change the position of the scales. By the way, this was already mentioned in the section on cover.

The role of energy "feed" for the muscles of these creatures is played by the anaerobic decomposition of glucose. Interestingly, most of the muscles (50-75%) can work even without oxygen saturation. Due to this, reptiles can cover short distances as quickly as warm-blooded animals. Muscles contract quickly. But if the creature "overdoes it", then lactic acid will actively accumulate in the muscles, the excess of which leads to fatigue. Therefore, representatives of this class, having made several runs, hide for rest. In a few hours, lactic acid breaks down, and the animal's strength is restored.

Musculature of snakes

About it it is necessary to tell separately. The general characteristics of the order of reptiles cannot convey all its specifics. The fact is that the muscles of the snake are used to move the food it swallowed inside, and not just for movement.

It is also important to know what the four main types of their movement are. The most famous is called serpentine, lateral or sliding. It is characterized by a wavy form of movement. It is this method that allows snakes to swim and reach high speeds. The record holder, by the way, is the poisonous black mamba living in Africa (lat. Dendroaspis polylepis). Its average speed is 11 km/h.

There is also a straightforward way of movement (the "caterpillar" technique). The snakes move forward on the skin of the abdomen, after which they pull up the entire back of the body. In the third method, called parallel, the animal seems to throw itself to the side (lateral cycle of movement). Seeing this is rare. This method is characteristic of snakes living on loose sand in deserts.

The fourth method is no less rare. It's called Concertina. Or, in other words, the accordion technique. It is used when moving a snake through a tree. It looks unusual, because the body seems to be going to form horizontal loops, after which the head rushes forward, due to which the "accordion" straightens.

All this is very unusual, but it explains the external structure and skeleton of reptiles. The general characteristic, of course, helps to understand approximately what it is “from the inside”, but by observing the movements described above, you can imagine everything visually.


Nervous system

It is also important to mention it when talking about the Reptile class. The general characteristics of the nervous system are detailed. But before discussing it, it is worth noting that the central nervous system of these creatures is represented by the spinal cord and the brain, consisting of five sections.

The first is the front. It is from his hemispheres that the olfactory lobes depart.

The second is intermediate. In its lower part is the pituitary gland, and in the upper part is the epiphysis. It is next to him, by the way, that the hatteria (the only modern representative of the beakhead order) and lizards develop an unpaired photosensitive organ called the parietal eye. And crocodiles, by the way, have neither the pituitary gland nor the epiphysis.

The third section is called the middle. It is represented by visual lobes. In this regard, the Reptile class also distinguished itself. The general characteristic makes it possible to understand that their middle section and visual cortex are much more developed than those of amphibians. The last component of the brain is the cerebellum. And another oblong section.

However, this is not all that is worth knowing about the Reptile class. The general characteristic, in short, makes it clear that representatives of this category of animals are distinguished by a developed physiological and anatomical structure. But it is also important to know that in their spinal cord the division into gray and white matter is much more clearly visible, unlike the same amphibians. They also have a pronounced parasympathetic and sympathetic autonomic nervous system. It is represented by a chain of paired nerve clusters (ganglia).


Sight and smell

This is perhaps the most interesting topic. And a general description of reptiles (or reptiles) will be incomplete without mentioning it.

So, these beings have six sense organs. The first is vision. Interestingly, many lizards are excellent at distinguishing colors. Hues are the most important means of their communication. They recognize poisonous insects by their color. And giant tortoises are also able to perceive colors. Many of them respond well to red. There is even a hypothesis that turtles can perceive infrared light.

Snakes and crocodiles do not distinguish colors. But in reptiles, the eye has the same structure as in humans. And some of their representatives have eyelids. Moreover, the lower ones are more mobile than the upper ones. The pupils, by the way, are different in reptiles. For representatives leading a nocturnal or twilight lifestyle, it is vertical. And in geckos, on narrowed pupils, you can even notice pinholes that focus an independent image on the retina. This feature ensures maximum sharpness of the reality displayed for the lizard.

As for the sense of smell. The general characteristics of reptiles can also tell about its specificity. In short, the main role in the sense of smell of these creatures is played by chemoreceptors. Due to them, these animals perceive the smell very well. They are able to find food buried at a depth of up to 8 centimeters. Vipers, snakes and monitor lizards, due to their sense of smell, can determine the type of an approaching animal long before it appears in the field of view. And crocodiles, lizards and turtles do have special glands, the secret of which is intended to “mark” the occupied territory. With an odorous substance, these creatures mark their sites.


Lifestyle

The general characteristics of reptiles can also tell about it. Grade 7 - at about this stage, this topic is being studied in high school.

So, the vast majority of animals belonging to this class are carnivores. Reptiles mainly feed on carrion and insects. But real predation is characteristic only of some lizards, crocodiles and snakes. Iguanas and agamas can eat anything - from vegetables and fruits to animal meat. However, there are also exclusively herbivorous creatures. These include land turtles.

The breeding is interesting. It is important to mention it when talking about the Reptiles (or Reptiles) class. The general description briefly explains how everything happens.

So, the Embryo develops, being in an egg, which is covered either with a calcareous or leathery shell. There is also ovoviviparity. Very rarely, cubs are born, as in viviparous animals. It is worth noting that caring for offspring is characteristic of these creatures. Female crocodiles, for example, carefully carry their babies in the oral cavity from masonry to water bodies.

It is also interesting to know that the vast majority of reptiles do not have a vocal apparatus. Nothing but a whistle or hiss, they can not publish. So no mating cries can be heard - these creatures are guided by the smell. Only eublefar lizards are capable of squeaking.

Well, the general characteristics and features of the external structure of reptiles were considered above. Finally, we can talk about some rare representatives.

The smallest creature of this class is living in deserts and semi-deserts. You can also meet him in areas where the Volga flows. This is an amazing creature, covered with granular scales. The length of his body reaches only 41 mm! Approximately the same tail, which is easily discarded.

Gyurza, which is the largest representative of the genus of giant vipers, also deserves attention. This is a poisonous creature weighing 3 kilograms, the length of which reaches 2 meters.

But, of course, the gyurza cannot be compared with the king cobra. After all, it is the largest poisonous snake. Some individuals reach a length of 5.6 m. Grow, by the way, throughout their lives. And they live up to 30 years.

A very attractive snake is McCoy's taipan. That's just a beautiful creature with golden-black scales is very dangerous. After all, this is the most poisonous land snake in the world. The poison of one individual (44 mg) is enough to kill a quarter of a million mice or 100 people.

This, of course, is far from all the amazing creatures that the Reptiles (or Reptiles) class abounds in. A general characteristic allows you to understand how great their diversity is. But it is also worth noting the attention of the Far Eastern skink. This is a lizard that can be found in Japan or the Kuril Islands. She, like all previously listed species, is listed in the Red Book of Russia. And its highlight is an amazing color, which can be appreciated by looking at the photo provided above.

Well, we can talk about this topic for a long time. After all, the world knows 9400 species of reptiles, and each of them is unique in its own way. But they can be viewed individually. All that has been said above may well arouse interest in this.

reptile class, or reptiles , has about 6 thousand species. These are real land animals.

Their development and flourishing are associated with changes in the Paleozoic and especially in the Mesozoic era of climatic conditions, a decrease in the number of wetlands, and a general warming of the climate. The origin of reptiles is due to the following aromorphoses :

- the appearance of protective shells around the egg;

- internal fertilization;

– direct development;

- the emergence of cellular lungs with developed airways;

- the appearance of a partial, and in crocodiles, a complete septum in the ventricle of the heart, which led to a partial separation of venous and arterial blood flows.

Important for life on land were such changes as internal fertilization, an increase in the anterior part of the brain and the appearance of a primary cortex in it.

The class of reptiles has 4 modern orders: Scaly (lizards, snakes), Turtles, Crocodiles, Beakheads (tuatara).

External building.Body reptiles is divided into sections - the head, trunk, tail and two pairs of limbs. There are sense organs - sight, hearing, smell, taste, touch. The body is flattened in the vertical direction and pressed against the ground.

Skin formed by keratinized epidermis, updated due to its lower layers, consisting of living cells. Horny shields protect against evaporation of moisture and desiccation. Moisture evaporates through the skin, but in desert animals these water losses are minimal. There are almost no skin glands. Reptiles grow during periodic molting.

Skeleton almost entirely skeletal. The skull retains cartilage in the olfactory and auditory regions. There are two sections in the skeleton of the head - cerebral and visceral (facial). Spine consists of the following departments:

- the cervical lizard consists of 8 vertebrae. The first and second vertebrae (atlas and epistrophy) serve to movably connect the skull with the spinal column;

- lumbar-thoracic - from 16 to 25 vertebrae, each of which carries a rib. The first five pairs form the chest, fusing with the sternum;

- sacral - 2 vertebrae, to which the pelvic bones are attached, forming the pelvic girdle;

- tail - sometimes several dozen vertebrae.

Skeleton of the girdle of the forelimbs formed by paired clavicles, scapulae and coracoids. The forelimb belt is stronger than that of amphibians. Free forelimbs similar in structure to the limbs of amphibians. Some representatives of the class lack limbs (snakes, legless lizards).

Pelvic girdle formed by paired, fused ischial, iliac and pubic bones. Free hind limbs have a characteristic, for terrestrial animals, structure.

in the muscular system intercostal muscles involved in breathing appear.

In the digestive system as features, conical teeth fused with bones, a long, muscular tongue, and the presence of a rudimentary caecum should be noted.

Respiratory system pulmonary type with developed airways - larynx, trachea, bronchi. An increase in the area of ​​the respiratory surface led to a more complete oxidation of the blood. The frequency of respiratory movements in reptiles depends on the ambient temperature. The higher it is, the faster the animal breathes.

Circulatory system closed. Two circles of blood circulation. The heart of most representatives is three-chambered, and in crocodiles it is four-chambered. Reptiles are cold-blooded animals with a relatively low level of metabolism, tk. mixed blood enters the cells of organs and tissues.

Nervous system develops, first of all, in the direction of an increase in the cerebral hemispheres. The rudiments of the primary cerebral cortex, formed by gray matter, appear. The cerebellum is well developed. In this regard, reptiles have more complex adaptive behavioral mechanisms. They show both complex unconditioned and conditioned reflexes.

excretory system formed by the kidneys, bladder and ureters. Reabsorption of water occurs in the renal tubules. In reptiles, it is not liquid urine that is excreted through the cloaca, but uric acid - a clot of filtered decay products. This prevents the animals from losing fluids.

sense organs developed and adapted to terrestrial existence. The eyes have eyelids and a nictitating membrane, the hearing organ consists of the inner and middle ear. There is only one bone in the middle ear. In the inner ear, the cochlea is somewhat isolated. There are organs of smell, touch and taste.

reproduction and the development of reptiles takes place on land. Fertilization is internal. There are ovoviviparous reptiles, as well as reptiles with a placenta (sea snakes).

The value of reptiles in nature and human life. Destroy insects, feeding on rodents, regulate their numbers; are eaten, the skin and shells are used to make various products; snake venom is used in pharmacology.

At sea and in the air. At the end of the Cretaceous period, most of the reptiles died out. Modern reptiles are just scattered remnants of that world.

Encyclopedic YouTube

  • 1 / 5

    In reptiles, both features of simpler amphibians and features of higher vertebrates are observed.

    Cover

    Muscular system

    The brain is located inside the skull. A number of important features distinguish the brain of reptiles from the brain of amphibians. Often they talk about the so-called sauropsid type of brain, which is also inherent in birds, in contrast to the ichthyopsid type in fish and amphibians.

    There are five sections of the reptile brain.

    • The forebrain consists of two large hemispheres, from which the olfactory lobes depart. The surface of the cerebral hemispheres is absolutely smooth. In the cerebral vault of the hemispheres, the primary vault is distinguished - archipallium, which occupies most of the roof of the hemispheres, and the beginnings of neopallium. The floor of the forebrain mainly consists of striatal bodies.
    • The diencephalon is located between the forebrain and midbrain. The epiphysis is located in its upper part, and the pituitary gland is located on the lower side. Most lizards and tuatara (as well as many extinct forms) develop a parietal eye next to the pineal gland, while crocodiles have lost both of these organs. The bottom of the diencephalon is occupied by the optic nerves and their decussation (chiasma).
    • The midbrain is represented by two large anterior hillocks - visual lobes, as well as small posterior hillocks. The visual cortex is more developed than in amphibians.
    • The cerebellum covers the anterior part of the medulla oblongata. It is larger compared to the amphibian cerebellum.
    • The medulla oblongata forms a bend in the vertical plane, which is characteristic of all amniotes.

    12 pairs of cranial nerves leave the brain. In the spinal cord, the division into white and gray matter is more distinct than in amphibians. Segmental spinal nerves depart from the spinal cord, forming a typical brachial and pelvic plexus. The autonomic nervous system (sympathetic and parasympathetic) is clearly expressed in the form of a chain of paired nerve ganglia.

    sense organs

    Reptiles have six main sense organs:

    Respiratory system

    Reptiles are characterized by suction-type breathing by expanding and contracting the chest with the help of the intercostal and abdominal muscles. The air that enters through the larynx enters the trachea - a long breathing tube, which at the end is divided into bronchileading to the lungs. Like amphibians, reptile lungs are sac-like, although their internal structure is much more complex. The inner walls of the lung sacs have a folded cellular structure, which significantly increases the respiratory surface.

    Since the body is covered with scales, there is no skin respiration in reptiles (the exceptions are soft-bodied turtles and sea snakes), and the lungs are the only respiratory organ.

    circulatory system

    Like amphibians, most reptiles have a three-chambered heartconsisting of a ventricle and two atria. The ventricle is divided by an incomplete septum into two halves: upper and lower. Crocodiles have a four-chambered heart.

    With this design of the heart, a gradient (difference) in the amount of oxygen in the blood is established in the slit-like space around the incomplete septum of the ventricle. After atrial contraction, the arterial blood from the left atrium enters the upper half of the ventricle and displaces the venous blood that has flowed from the right side of the ventricle into the lower half. Mixed blood appears in the right side of the ventricle. When the ventricle contracts, each portion of blood rushes to the nearest opening: arterial blood from the upper half to the right aortic arch, venous blood from the lower half to the pulmonary artery, and mixed blood from the right side of the ventricle to the left aortic arch. Since it is the right aortic arch that carries blood to the brain, the brain receives the most oxygenated blood. In crocodiles, the septum completely divides the ventricle into two halves: the right - venous and left - arterial, thus forming a four-chambered heart, almost like in mammals and birds.

    In contrast to the common arterial trunk of amphibians, there are three independent vessels in reptiles: the pulmonary artery and the right and left aortic arches. Each arch of the aorta curves back around the esophagus, and, converging with each other, they are connected to the unpaired dorsal aorta. The dorsal aorta stretches back, sending arteries along the way to all organs. From the right arch of the aorta, extending from the left arterial ventricle, the right and left carotid arteries branch off with a common trunk, and both subclavian arteries, carrying blood to the forelimbs, depart from the right arch.

    A complete division into two independent circles of blood circulation in reptiles (including crocodiles) does not occur, since venous and arterial blood are mixed in the dorsal aorta.

    Like fish and amphibians, all modern reptiles are cold-blooded animals. Despite this, many reptiles can regulate their temperature by moving from shade to sun and back again, or by changing color, becoming darker to warm up or lighter to cool off.

    Digestive system

    Due to the variety of food available for food, the digestive tract of reptiles is much more differentiated than that of amphibians.

    The digestive system begins with a mouth opening, limited by jaws with conical, identical, firmly accreting teeth (homodont system). The tongue is free, muscular in front, mobile, thinning and bifurcating towards the end. The oral cavity is separated from the pharynx by a developing secondary bony palate. Multicellular salivary glands contain digestive enzymes. The pharynx passes into a narrow esophagus, then into the muscular stomach and intestines. The stomach has thick muscular walls. On the border between the small and large intestines is the caecum, which amphibians do not have. The large liver of reptiles has a gallbladder. The pancreas in the form of a long dense body lies in the loop of the duodenum. The intestine ends in a cloaca.

    excretory system

    The kidneys of reptiles differ significantly from the kidneys of fish and amphibians, which have to solve the problem of getting rid of a constant excess of water in the body. Instead of the trunk kidneys of amphibians (mesonephros), the kidneys of reptiles (metanephros) are located in the pelvic region on the ventral side of the cloaca and on its sides. The kidneys are connected to the cloaca through the ureters.

    The thin-walled stalked bladder is connected to the cloaca by a thin neck on its ventral side. In some reptiles, the bladder is underdeveloped (crocodiles, snakes, some lizards).

    A new excretory organ, the pelvic kidney, also appears.

    In terrestrial reptiles, the end product of nitrogen metabolism is uric acid.

    reproductive system

    Reptiles are dioecious animals, bisexual reproduction.

    male reproductive system consists of a pair of testes that are located on the sides of the lumbar spine. From each testicle, a seminal canal departs, which flows into the wolffian canal. With the appearance of the trunk kidney in reptile wolfs, the canal in males acts only as a vas deferens and is completely absent in females. The Wolffian duct opens into the cloaca to form the seminal vesicle.

    Reproductive system of females represented by the ovaries, which are suspended on the mesentery to the dorsal side of the body cavity on the sides of the spine. The oviducts (Müllerian channels) are also suspended from the mesentery. In the anterior part of the body cavity, the oviducts open with slit-like openings - funnels. The lower end of the oviducts opens into the lower part of the cloaca on its dorsal side.

    Lifestyle

    Development

    Fertilization is internal. The development of the embryo takes place in the egg. Reptiles have direct postembryonic development. Many representatives are characterized by caring for offspring, in particular, female crocodiles carry offspring from the place of laying to reservoirs in the oral cavity, although in some cases they can eat the cub.

    Food

    Most reptiles are carnivores. Some (for example, agamas, iguanas) are characterized by a mixed diet. There are also almost exclusively herbivorous reptiles (land turtles).

    Movement

    For most reptiles, the characteristic mode of movement is crawling. Many species are good swimmers. Several genera are capable of gliding flight, active flying reptiles are known only from fossils (see Pterosaurs).

    Voice

    Most reptiles do not have a real vocal apparatus and can make only the most primitive sounds like hissing or whistling. Their voices are the same.

    Economic importance

    The value of reptiles for humans is relatively small. The skin of crocodiles, large snakes and lizards is used in the leather industry for the manufacture of suitcases, belts, shoes, etc., however, these items are exclusive, being a luxury item. The meat and eggs of many turtles are eaten. Some lizards and snakes may also be eaten. Snake venom is used in medicine. Many snakes are useful in exterminating rodents, and lizards are insects. Some types of reptiles are kept as pets.

    Poisonous snakes pose a great danger to people, especially in tropical countries. Large crocodiles are dangerous to humans, causing damage to livestock. Many turtles harm fisheries.

    Origin of reptiles

    The first representatives of reptiles - cotylosaurs - are known from the Middle Carboniferous. By the end of the period, animal-like reptiles appear, which in the Permian period settled almost throughout the land, becoming the dominant group among reptiles. In the Mesozoic era, the flowering of reptiles begins, among the representatives there is the greatest diversity. There is a development of sea and river reservoirs, as well as air space. In the Mesozoic, the formation of all groups of reptiles occurs. The last group - snakes - formed in the Cretaceous period.

    At the end of the Cretaceous period, there is a sharp decrease in the number of reptile species. Modern science cannot yet unequivocally indicate the causes of extinction.

    Phylogenetics

    Amniota





    Reptilia


    Eureptilia


    Romeriida

    paleothyris acadiana








    Model objects

    In 2011, the reptile genome was deciphered - caroline anole lizard. Thus this reptile entered the circle

    Reptiles are the first class of true primary terrestrial vertebrates (Amniota). Relatively large, rich in yolk and protein, the eggs are covered with a dense parchment-like shell. Fertilization is only internal. Embryonic development takes place in the air with the formation of embryonic membranes - amnion and serosa - and allantois; the larval stage is absent. A young animal hatched from an egg differs from adults only in size.

    The class Reptilia is characterized by development from eggs, which, unlike amphibians, have an amniotic membrane, which allowed them to adapt to the conditions of existence on land. Thus, reptiles are the first fully terrestrial vertebrates. A huge number of fossil orders of reptiles are known (including, of course, terrible lizards - dinosaurs), but only four now exist:

    The dry skin of reptiles is almost devoid of glands. The outer layers of the epidermis become keratinized; horny scales and scutes form in the skin. Breathing is only lung. Airways are formed - the trachea and bronchi. Breathing is carried out with movements of the chest. The heart is three-chambered. Three blood trunks independently depart from the ventricle divided by an incomplete septum: two aortic arches and a pulmonary artery. The carotid arteries supplying the head arise only from the right aortic arch. The large and small circles of blood circulation are not completely separated, but the degree of their separation is higher than that of amphibians. Excretion and water exchange are provided by metanephric (pelvic) kidneys. The relative size of the brain increases, especially due to the increase in the hemispheres and cerebellum.

    The skeleton is completely ossified. The axial skeleton is divided into five sections. Elongation of the neck and specialized first two cervical vertebrae (atlas and epistrophe) provide high head mobility. The skull has one occipital condyle and well developed integumentary bones; the formation of temporal pits and the bone temporal arches limiting them is characteristic.

    Terrestrial-type limbs with intercrystal and intertarsal articulations. The girdle of the forelimbs is connected to the axial skeleton through the ribs, the pelvic girdle articulates with the transverse processes of the two sacral vertebrae.

    They inhabit a variety of terrestrial habitats mainly in warm, partly in temperate latitudes; some of the species again switched to an aquatic way of life. The general level of vital activity is noticeably higher than that of amphibians. However, body temperature is not constant and largely depends on the ambient temperature (

    General characteristics of the Class Reptiles


    Reptiles (reptiles - from lat. Reptilia). There are 8734 species of reptiles known in the world. There are 72 species on the territory of Russia, 6 species live on the territory of the Vladimir region.

    Structure

    In reptiles, both features of simpler amphibians and features of higher vertebrates are observed.

    Cover

    The outer skin of reptiles, as a result of thickening and keratinization, forms scales or scutes. In lizards, horny scales overlap each other, resembling roof tiles. In turtles, fused shields form a solid, durable shell. The change of the horny cover occurs by complete or partial molting, which in many species occurs several times a year.

    Thick and dry skin contains odorous glands. Mucous glands are absent.

    In the outer part of the inner layer of the skin, there are often special cells - chromatophores. These cells secrete pigments: melanins and carotenoids. Also found in chromatophores is guanine, which is capable of reflecting light. Thanks to chromatophores, some reptiles are able to change the color of their body in a relatively short time. Chameleons are the most famous representatives with a similar property.

    Skeletal system

    In the axial skeleton of reptiles, the division into sections is more noticeable than in amphibians. Four parts of the skeleton are clearly distinguishable: cervical (lat. pars cervicalis), trunk (lumbar-thoracic, pars thoracolumbalis), sacral (pars sacralis) and tail (pars caudalis).

    Typical for reptiles is the following structure of the axial skeleton. The total number of vertebrae is different in different species (50-80, in snakes it increases to 140-435). Of the vertebrae of the cervical region (from 7 to 10), the two anterior ones (atlas and epistrophy) form a joint that allows the head not only to move in a vertical plane relative to the first cervical vertebra, but also to turn. In the trunk region there are from 16 to 25 vertebrae, each with a pair of ribs. The first few vertebrae attach to the sternum to form the ribcage (absent in snakes). There are only two vertebrae in the sacral region, to the wide transverse processes of which the pelvis is attached. The caudal section consists of several dozen (15-40) vertebrae, gradually decreasing in size. The last tail vertebrae are small rod-shaped bones.

    In some groups of reptiles, the axial skeleton has differences. In snakes, the spine is clearly divided only into the trunk and tail sections, the sternum is absent. In turtles, the vertebrae of the trunk are fused with the dorsal shield of the shell, as a result of which they are motionless.

    The skull of reptiles is much more ossified than that of amphibians. Only the olfactory capsule and auditory region contain a small amount of cartilage. The axial and visceral regions of the skull are embryonically formed separately, but in adults they fuse into a single formation. The structure of the skull includes both cartilaginous (replacing, or primary) and numerous skin (integumentary, or secondary) bones.

    The girdle of the forelimbs is similar to the girdle of amphibians, differing only in a stronger development of ossification. The forelimb of a reptile consists of a shoulder, forearm and hand. Back - from the thigh, lower leg and foot. Claws are located on the phalanges of the limbs.

    Muscular system

    The muscular system of reptiles is represented by chewing, cervical muscles, abdominal muscles, as well as flexor and extensor muscles. There are intercostal muscles characteristic of amniotes, which play an important role in the act of breathing. The subcutaneous musculature allows you to change the position of the horny scales.

    Nervous system

    Like most chordates, the nervous system of reptiles is represented by the brain and spinal cord.

    The brain is located inside the skull. A number of important features distinguish the brain of reptiles from the brain of amphibians. Often they talk about the so-called sauropsid type of brain, which is also inherent in birds, in contrast to the ichthyopsid type in fish and amphibians.

    There are five parts of the reptile brain:

    * The forebrain consists of two cerebral hemispheres, from which the olfactory lobes depart. The surface of the cerebral hemispheres is absolutely smooth. In the cerebral vault of the hemispheres, the primary vault is distinguished - the archipallium, which occupies most of the roof of the hemispheres, and the beginnings of the neopallium. The floor of the forebrain mainly consists of the striatum.

    * The diencephalon is located between the forebrain and midbrain. In its upper part is the parietal organ, and on the lower side is the pituitary gland. The bottom of the diencephalon is occupied by the optic nerves and their decussation (chiasm).

    * The midbrain is represented by two large anterior hills - the visual lobes, as well as small posterior hills. The visual cortex is more developed than in amphibians.

    * The cerebellum covers the anterior part of the medulla oblongata. It is larger than the amphibian cerebellum.

    * The medulla oblongata forms a bend in the vertical plane, which is characteristic of all amniotes.

    12 pairs of cranial nerves leave the brain. In the spinal cord, the division into white and gray matter is more distinct than in amphibians. Segmental spinal nerves depart from the spinal cord, forming a typical brachial and pelvic plexus. The autonomic nervous system (sympathetic and parasympathetic) is clearly expressed in the form of a chain of paired nerve ganglia.

    sense organs

    Reptiles have six main sense organs:

    * The organ of vision - the eyes, are more complex than those of frogs: in the sclera there is a ring of thin bone plates; an outgrowth departs from the back wall of the eyeball - a scallop that protrudes into the vitreous body; striated muscles are developed in the ciliary body, which allows not only to move the lens, but also to change its shape, thus focusing in the process of accommodation. The organs of vision have adaptations to work in the air. The lacrimal glands keep the eye from drying out. The outer eyelids and nictitating membrane perform a protective function. In snakes and some lizards, the eyelids fuse together to form a transparent membrane. The retina of the eye can contain both rods and cones. Nocturnal species lack cones. In most diurnal species, the range of color vision is shifted to the yellow-orange part of the spectrum. Vision is crucial among the sense organs of reptiles.

    * The olfactory organ is represented by the internal nostrils - choanae and the vomeronasal organ. Compared to the structure of amphibians, the choanae are located closer to the pharynx, which makes it possible to breathe freely while food is in the mouth. The sense of smell is better developed than that of amphibians, allowing many lizards to find food that is under the surface of the sand at a depth of up to 6-8 cm.

    * Organ of taste - taste buds located mainly in the pharynx.

    * The organ of thermal sensitivity is located in the facial fossa between the eye and nose on each side of the head. Especially developed in snakes. In pit vipers, thermolocators even make it possible to determine the direction of the source of thermal radiation.

    * The organ of hearing is close to the organ of hearing of frogs, it contains the inner and middle ear, equipped with the tympanic membrane, the auditory ossicle - the stirrup and the Eustachian tube. The role of hearing in the life of reptiles is relatively small; hearing is especially weak in snakes that do not have an eardrum and perceive vibrations propagating along the ground or in water. Reptiles perceive sounds in the range of 20-6000 Hz, although most hear well only in the range of 60-200 Hz (crocodiles have 100-3000 Hz).

    * The sense of touch is pronounced, especially in turtles, which can feel even a light touch on the shell.

    Respiratory system

    Reptiles are characterized by suction-type breathing by expanding and contracting the chest with the help of intercostal and abdominal muscles. The air that enters through the larynx enters the trachea - a long respiratory tube, which at the end divides into the bronchi leading to the lungs. Like amphibians, reptile lungs are sac-like, although their internal structure is much more complex. The inner walls of the lung sacs have a folded cellular structure, which significantly increases the respiratory surface.

    Since the body is covered with scales, there is no skin respiration in reptiles (the exceptions are soft-bodied turtles and sea snakes), and the lungs are the only respiratory organ.

    The circulatory system of reptiles

    Like amphibians, most reptiles have a three-chambered heart, consisting of one ventricle and two atria. The ventricle is divided by an incomplete septum into two halves: upper and lower. With this design of the heart, a gradient (difference) in the amount of oxygen in the blood is established in the slit-like space around the incomplete septum of the ventricle. After atrial contraction, the arterial blood from the left atrium enters the upper half of the ventricle and displaces the venous blood that has flowed from the right side of the ventricle into the lower half. Mixed blood appears in the right side of the ventricle. When the ventricle contracts, each portion of blood rushes to the nearest opening: arterial blood from the upper half into the right aortic arch, venous blood from the lower half into the pulmonary artery, and mixed blood from the right side of the ventricle into the left aortic arch. Since it is the right aortic arch that carries blood to the brain, the brain receives the most oxygenated blood. In crocodiles, the septum completely divides the ventricle into two halves: the right - venous and left - arterial, thus forming a four-chambered heart, almost like in mammals and birds

    In contrast to the common arterial trunk of amphibians, there are three independent vessels in reptiles: the pulmonary artery, and the right and left aortic arches. Each arch of the aorta curves back around the esophagus, and, converging with each other, they are connected to the unpaired dorsal aorta. The dorsal aorta stretches back, sending arteries along the way to all organs. From the right arch of the aorta, extending from the left arterial ventricle, the right and left carotid arteries branch off with a common trunk, and both subclavian arteries, which carry blood to the forelimbs, also depart from the right arch.

    A complete division into two independent circles of blood circulation in reptiles (including crocodiles) does not occur, since venous and arterial blood are mixed in the dorsal aorta.

    Like fish and amphibians, all reptiles are cold-blooded animals.

    Digestive system

    Due to the variety of food available for food, the digestive tract of reptiles is much more differentiated than that of amphibians.

    The stomach has thick muscular walls. On the border between the small and large intestines is the caecum, which amphibians do not have. The large reptile liver has a gallbladder. The pancreas in the form of a long dense body lies in the loop of the duodenum. The intestine ends with a cloaca.

    excretory system

    The excretory system of reptiles is represented by the kidneys, ureters and bladder.

    The kidneys of reptiles differ significantly from the kidneys of fish and amphibians, which have to solve the problem of getting rid of a constant excess of water in the body. Instead of the trunk kidneys of amphibians (mesonephros), the kidneys of reptiles (metanephros) are located in the pelvic region on the ventral side of the cloaca and on its sides. The kidneys are connected to the cloaca through the ureters.

    The thin-walled stalked bladder is connected to the cloaca by a thin neck on its ventral side. In some reptiles, the bladder is underdeveloped (crocodiles, snakes, some lizards).

    A new organ of excretion also appears - the pelvic kidney.

    In terrestrial amphibians, the end product of nitrogen metabolism is urea.

    reproductive system

    Reptiles are dioecious animals.

    The male reproductive system consists of a pair of testes, which are located on the sides of the lumbar spine. From each testicle, a seminal canal leaves, which flows into the wolfian canal. With the appearance of the trunk kidney in reptile wolfs, the canal in males acts only as a vas deferens and is completely absent in females. The Wolffian duct opens into the cloaca to form the seminal vesicle.

    The female reproductive system "is represented by the ovaries, which are suspended on the mesentery to the dorsal side of the body cavity on the sides of the spine. The oviducts (Müllerian canals) are also suspended on the mesentery. In the anterior part of the body cavity, the oviducts open with slit-like holes - funnels. The lower end of the oviducts opens into the lower part of the cloaca on her back.

    Development:

    Fertilization is internal. The development of the embryo takes place in the egg. Reptiles have direct postembryonic development.

    Most reptiles are carnivores. Some (for example, agamas, iguanas) are characterized by a mixed diet. There are also almost exclusively herbivorous reptiles (land turtles).

    Most reptiles do not have a real vocal apparatus and can make only the most primitive sounds like hissing or whistling. Their voices are the same.

    Reptiles of the Vladimir region

    It has a long spindle-shaped body. Young spindles are a very beautiful silvery-white or light cream color above, with two thin dark lines running along the ridge, closely spaced, starting from a more or less triangular spot located on the back of the head. The sides of the body and their belly are black-brown or almost black, and the border between the light dorsal and dark lateral body coloration is very pronounced. As the animal grows, the upper side of the body gradually darkens and acquires brown, brownish or bronze tones, while the sides become noticeably lighter, but usually remain darker than the back. blue spots.The length of this lizard reaches 60 cm, more than half of which falls on a very brittle, slightly pointed tail at the end.

    Lifestyle. Lives in deciduous and mixed forests, also found in bushes, meadows, fields and gardens, but usually near the forest. It hides in rotten stumps, under fallen tree trunks, in heaps of deadwood, in the thickness of the forest floor, under stones and in anthills. Often, the spindle makes a hole for itself, digging its head into the forest litter or loose soil. Her movements on level ground are very slow, however, making her way among vegetation or between stones, she moves quite quickly, wriggling her whole body in a serpentine way. In the spring, the first time after wintering, the spindles bask in the sun for a long time and are not uncommon in the places where they live. However, already from mid-June, and in the south much earlier, these lizards switch to a twilight and nocturnal lifestyle and very rarely leave their shelters during the daytime, usually in cloudy but warm weather or after heavy night rain. The spindles feed on earthworms, terrestrial molluscs, insect larvae, centipedes and other slow moving animals, since they are not able to keep up with more mobile prey. Noticing the prey, the spindle slowly approaches it, first feels it with its tongue, then opens its mouth wide and slowly grabs it. Sharp, bent back teeth securely hold slippery writhing worms and naked slugs in the mouth, which the lizard slowly swallows, alternately tilting its head to one side or the other. In the event that the captured worm firmly clings to the soil in the earthen hole with the rear end of the body, the spindle, stretching in length, begins to rapidly rotate in one direction, thus tearing off part of the prey. They do the same when together they grab one long worm or slug and, rotating in different directions, quickly twist the prey in half. Eating snails, the spindle gradually rests its head more and more against the mouth of the shell and little by little pulls the mollusk out of its shelter. 2.5-3 months after the mating that takes place in the spring, the female gives birth to from 5 to 26 cubs, which are born in a transparent facial shell, which they immediately tear and spread to the sides. The length of young lizards immediately after birth usually does not exceed 100 mm, including the tail. Spindles hibernate in rodent burrows, in the depths of rotten stumps, sometimes gathering 20-30 or more individuals together. Due to its slowness and complete defenselessness, this lizard often becomes a victim of various enemies, from which only a long and extremely brittle tail, remaining in the teeth or claws of a predator, helps it to escape. In many places, the spindle is considered poisonous and, mistaking for a snake, is mercilessly exterminated. In reality, the spindle is completely harmless and only benefits a person, destroying various pests in many ways. Like the yellow-bellied lizard, this lizard tolerates captivity very well and quickly gets used to a person. There are cases when she survived in captivity for 20-30 and even 50 years.

    The lizard is agile. Young lizards of this species are brownish-gray or brownish on top with three light narrow stripes edged with black, the middle of which stretches along the ridge, and both lateral ones pass along the sides of the back and are lost on the tail. Small white eyes are usually located in one row on the sides of the body. With age, this coloring changes. The light body stripes blur and become less clear, and individual irregularly shaped dark brown or completely black spots appear along the ridge, located in one or two parallel rows, and in the latter case they are separated by a light median line. The color of the body also changes greatly. In males, it acquires a salad, olive or green color, while in females it becomes brown, or brownish-brown, or much less often green, like in males. Often, the dorsal pattern is completely or partially absent and the animal acquires a monochromatic green or brownish-brown color. The belly is usually white or greenish-white in females and greenish in males, usually with rather large dark spots. During the breeding season, the color becomes brighter, which primarily applies to green males. The length of the lizard does not exceed 25 - 28 cm, including the tail.

    The agile lizard everywhere prefers dry and sunny areas, inhabiting the steppes, not too dense forests, gardens, groves, copses, hillsides and ravines, bushes, roadsides, railway embankments and the like. In the speed of its movements, the agile lizard is noticeably inferior to the green and striped one, yet, justifying its name, it runs so fast that it is quite difficult to catch it with your hands, especially since the animal is very careful and rarely moves more than 10-15 m from its shelter . Fleeing from persecution, this lizard suddenly abruptly turns its tail to the side during its entire course and, “making a half turn on the spot, turns its head towards the pursuer. By performing this maneuver and changing the direction of the run several times in a row with amazing speed, the animal often completely confuses the pursuer. Often the lizard escapes on the trees, and, like a squirrel, it rises in a helical fashion along the trunk. When caught, it strenuously breaks out, opens its mouth wide and, on occasion, can quite strongly cling to a finger. In the middle lane, quick lizards wake up in spring, in the second half of April or early May. As a rule, young lizards leave their winter shelters one to two weeks later than older ones. From early morning, as soon as the sun warms the earth a little, the lizards come out of their holes and bask at the entrance. At the same time, they begin to hunt for beetles, grasshoppers, caterpillars, worms, spiders and other small invertebrates. Noticing the prey, the lizard becomes alert, follows it with its eyes for some time, and then quickly takes off and grabs it. She first shakes large grasshoppers and beetles in her mouth for a long time, releasing them to the ground from time to time and then grabbing them again. At the same time, she tears off their hard chitinous parts - elytra and legs, and then swallows the rest whole. Having swallowed the prey, it carefully licks its lips and, rising on its front legs, slowly bends the front of the body, thus helping the fastest passage of food. There are known cases of large males eating young lizards of their own species, as well as eggs laid by females. Settling in apiaries, nimble lizards feed on bees, which brings some harm to beekeeping. Even from a distance, having heard the characteristic buzz of a bee returning with a bribe, the lizard becomes alert, raises its head and then, with a quick and precise movement, jumping up, grabs the insect often before it lands on the notch. However, the harm brought in this way is certainly compensated by the benefits from the destruction of a large number of pests in agriculture and forestry. The lizard, satiated as a result of the morning hunt, settles again on the sun, changing its place from time to time and moving away from the approaching shadow. When her body is strongly heated by the sun, the lizard lies on its belly, raises its legs and tail, and, shaking its head, quickly opens and closes its mouth. In such a tense state, it usually remains only for a few seconds, then hastily disappears into the shadows or begins to rapidly run from place to place. At noon, most lizards take refuge in shelters, reappearing in the afternoon, when the heat subsides somewhat. By sunset, the lizards hide in holes. In the spring, during the breeding season, briskly running males often rise on their front legs and look around. Noticing the female from afar, the male immediately begins to pursue her and, overtaking her, after several unsuccessful attempts, grabs her by the tail. The female immediately stops, and her tail begins to wriggle quickly. Further, the male, without letting his tail out of his mouth, begins to slowly move his head up to its base, until he finally grabs the female by the side, in front of the hind legs. When this is achieved, he bends the body in one sharp movement, and mating occurs. When meeting with each other, the males immediately rise on their outstretched front legs, strongly compress the front part of the body from the sides and begin to slowly approach each other sideways. Sometimes one of them, obviously weaker, breaks down and takes to flight. However, more often fierce fights occur between males. Each opponent tries to grab the opponent by the neck or the back of the head and turn him over onto his back, which is achieved by a sharp lateral movement of the head. The defeated male lies on his back, usually for only a few moments, the next second he gets to his feet and quickly takes to flight, and the winner, not content with the victory he has won, starts pursuing him. More often, however, battles between males end with one of them falling with his open jaw into the mouth of the other, and both of them roll on the ground in a complete frenzy with their eyes closed, until finally the weaker of them breaks out and runs away. During the mating season, adult lizards break in pairs and settle together in one hole, in the vicinity of which they hunt together and bask in the sun. In late May - early June, the female lays from 6 to 16 eggs, burying them in a shallow hole or leaving them in the depths of the hole. Young appear from the end of July. Lizards usually overwinter in summer burrows, the entrance to which is clogged with leaves and earth. In the middle lane, adults usually leave for wintering at the beginning of September. The agile lizard tolerates captivity very well, quickly gets used to a person and begins to take food from the hands.

    The lizard is viviparous. Newly born viviparous lizards are dark brown or almost black in color, often without any pattern. As they grow, their color gradually brightens, and over time a characteristic pattern appears, consisting of a dark narrow strip along the ridge, two light stripes on the sides of the back, and relatively wide dark stripes on the sides of the body. In addition, small dark spots are scattered all over the body in disorder. The undersides of adult males are orange or brick red, while those of females are whitish-gray, yellowish or greenish. There are also completely black specimens. The length of viviparous lizards does not exceed 15 - 18 cm, of which more than half is occupied by the Tail, somewhat thickened at the base in males. Unlike most other true lizards, females of this species are larger than males.

    Lifestyle. Throughout most of its vast range, the viviparous lizard adheres to wet habitats, meeting in forested areas of swamps, peat bogs, overgrown clearings, forest edges and clearings, in deciduous and coniferous forest nurseries, on the banks of streams and canals overgrown with shrubs, and in similar places. On forest clearings and edges, lizards most readily settle at individual stumps, fallen trees, at the base of bushes and between tree roots. They do not dig their own burrows and use rodent burrows or spaces under loose bark on stumps and dry trees for housing; in the mountains they hide under rocks. In case of danger, these lizards often escape in the water and, having run some distance along the bottom, burrow into the silt or fallen leaves covering the bottom of the reservoir. In spring, the viviparous lizard wakes up from hibernation quite early, when there are still individual patches of snow in the forest. On forest clearings and edges, individual trees are completely overgrown at the base with tall grasses, and the lizards that settled here climb 1-2 m up the trunk, where they hunt for insects. At the end of the day, sometimes several lizards can be observed on the illuminated side of the trunk. Viviparous lizards feed on various insects, spiders, mollusks, worms, getting them not only on the ground, but also on herbaceous plants and tree trunks. Mating takes place shortly after awakening in April - May. Unlike all other species of its kind, this lizard gives birth to live young. Pregnancy lasts about 90 days, and young individuals (8-12) appear in mid-July - late August. According to the observations of I. S. Darevsky, in extremely rare cases they overwinter inside the female and are born in the spring of the next year. “Before the onset of childbirth,” writes A. M. Nikolsky, “the female becomes restless, scrapes the ground, bends her tail over her back ... and finally in the evening she will give birth to the first cub, usually sitting still in the facial shell; two minutes later, the second is born, and so on. After each clutch, she takes a few steps forward so that the cubs lie in a line. Not later than half an hour later they crawl out of the shells. The mother begins to run back and forth and shows no concern for her children. Sometimes she returns to the place of masonry, but only to eat part of the facial shells. For the first days of their lives, cubs sit in the cracks of the earth, curling their tails, and do not go out in search of food.

    Already ordinary. The most famous and widespread species of the genus. It is already well distinguished from all our other snakes by two large, clearly visible light spots (yellow, orange, off-white) located on the sides of the head. These spots are semi-lunar in shape and bordered in front and behind by black stripes. Sometimes there are individuals in which light spots are weakly expressed or absent. The color of the upper side of the snake's body is from dark gray or brown to black, the belly is white, however, an uneven black stripe stretches along the midline of the abdomen, which in some individuals is so widened that it displaces almost all the white color that remains only in the throat area. The body length of the snake can reach 1.5 m, but usually does not exceed 1 m; females are noticeably larger than males.

    The habitats of snakes are very diverse, but certainly quite wet. Snakes are especially numerous along the banks of calm rivers, lakes, ponds, grass swamps, in moist forests and floodplain meadows covered with bushes, but sometimes they are found even in the open steppe and in the mountains. They often live in vegetable gardens, gardens, barnyards and sometimes crawl into various outbuildings. In spring, and also in autumn, when the soil stores a lot of moisture, snakes can go far from water. The shelters of snakes are voids under the roots of trees, heaps of stones, rodent burrows, haystacks, gaps between the logs of bridges, dams and other shelters. Sometimes snakes settle in basements, under houses, in heaps of manure or garbage. In fallen leaves and loose soil, snakes can make their own moves. Common snakes are very active, agile snakes. They crawl quickly, can climb trees and swim well with the help of the lateral bends of the body characteristic of snakes. Snakes can move away from the coast for many kilometers and stay under water for several tens of minutes without surfacing. Usually they swim, raising their heads above the surface of the water and leaving characteristic ripples behind them, so the snakes moving along the pond are clearly visible. Snakes are active during daylight hours, and hide in shelters at night. They hunt mainly in the morning and evening hours. During the day they like to bask in the sun, curled up on the creases of reeds, stones, trees bent over the water, hummocks, nests of water birds. In the hottest time, especially in the south, they hide in the shade or descend into the water, where they can lie at the bottom for a long time. The snakes start mating at the end of April - May, after the first spring molt. In July - August females lay from 6 to 30 soft, parchment-covered eggs in one portion, which often stick together like a rosary. Eggs easily die from drying out, so snakes lay them in damp, but well-preserved heat (25-30 °) shelters: under fallen leaves, in damp moss, heaps of manure and even garbage dumps, abandoned rodent burrows, rotten stumps. Sometimes, especially when there is a lack of suitable shelters, several females lay eggs in one place. A case is described when over 1200 snake eggs were found under an old door lying in a forest clearing, arranged in several layers. The initial stages of development of the snake embryo still pass in the mother's body, and in the newly laid eggs, the pulsation of the heart of the embryo is noticeable to the naked eye. Incubation lasts about 5-8 weeks. Young snakes at the time of exit from the eggs are about 15 cm long; they immediately spread and begin to lead an independent lifestyle. The young lead a much more secretive life than the adults, and are comparatively rarely seen. For the winter, snakes take refuge in deep rodent burrows, in cracks in coastal cliffs, under the roots of rotten trees. Sometimes they winter alone, often several individuals together, and do not avoid the close proximity of snakes of other species. They leave for wintering relatively late, in October - November, when night frosts already begin. Awakening from hibernation occurs in March - April. On warm days, snakes begin to crawl out of their winter shelters and bask near them in the sun for a long time, sometimes gathering into balls of many individuals together. With each spring day, the snakes become more active and gradually creep away from their wintering places.

    They feed on small frogs, toads and their young. Occasionally, lizards, small birds and their chicks, as well as small mammals, including newborn cubs of water rats and muskrats, become their prey. Young snakes often catch insects. The common belief that snakes feed on fish and are very harmful to fish farming is based on a misunderstanding. Small fish are eaten by these snakes rarely and in small quantities. Even in reservoirs rich in fish, snakes sometimes swim among such dense flocks of fry that they literally push them aside with their bodies, and yet in the stomachs of caught snakes it was possible to find not fish, but only young frogs. For one hunt, a large one can swallow up to 8 frogs or large tadpoles of a lake frog. The frogs that are pursued by snakes behave in a very peculiar way: although it would be easier for them to escape with large jumps, they make short and rare jumps and make a cry that is completely different from the sounds we are used to hearing from them. This cry is more like the mournful bleating of a sheep. The pursuit rarely lasts long, and usually the snake very soon overtakes its prey, grabs it and immediately begins to swallow it alive. Usually he tries to grab the frog by the head, but often he fails, and he grabs it by the hind legs and begins to slowly pull it into his mouth. The frog beats violently and makes croaking sounds. It swallows small frogs easily, but sometimes it spends several hours devouring large individuals. If the snake is in danger, then it usually regurgitates, like other snakes, the swallowed prey, and it opens its mouth very wide if the swallowed animal was large. There were cases that snakes belched live frogs, which, despite the fact that they had been in the throat of a snake, turned out to be quite viable in the future. Like all snakes, snakes are able to do without food for a long time. A case is known when a snake starved for more than 300 days without harm to itself. They drink snakes, especially on hot days, a lot. There are a lot of enemies already. They are eaten by serpent eagles, storks, kites and many predatory mammals (raccoon dogs, foxes, minks, martens). Serious enemies of snakes are also rats that eat clutches and young snakes. From a person, snakes always try to hide by flight. Unable to crawl away, sometimes they (especially large individuals) take a threatening posture: they curl up in a ball and from time to time throw their heads forward with a loud hiss. Being caught, the snakes bite, but only in exceptionally rare cases, inflicting light, quickly healing scratches with their teeth. The only means of protection for snakes should be considered an extremely smelly yellowish-white liquid that they release from the cloaca. In many cases, the caught snake quickly stops resisting, throws out the prey from the stomach if it has been eaten recently, and then completely relaxes the body, opens its mouth wide and, with its tongue hanging out, hangs lifelessly in its hands or rolls over onto its back. This state of "imaginary death" quickly passes if the snake is thrown into the water or simply left alone. The snakes live well in captivity, quickly begin to take the food offered to them and soon become completely tame. They need water for drinking and bathing.

    Copperhead common. The length of the body is up to 65 cm. The color of the back varies from gray, gray-brown and yellowish-brown to red-brown and copper-red. Reddish tones are especially characteristic of males. Small dark spots stretch along the back in 2-4 longitudinal rows, which in some specimens almost merge with each other and are clearly visible, while in others, on the contrary, they are weakly expressed. There are two brown or black-brown stripes (or two spots) on the neck, usually merging at the back of the head. The head is dark from above or with a characteristic pattern of an arcuate strip cut in front in front of the eyes and a broken line passing through the supraorbital and frontal scutes. A narrow brown stripe runs from the nostril through the eye and further to the ear. The underside of the body is gray, bluish-steel, brownish, orange-brown, pink or almost red, usually with dark blurred spots or speckles.

    It is found most often in dry hilly areas among bushes and forest edges, but can also be found in dense forest, meadows and even in the steppe. It rises to the mountains up to a height of 3000 m, choosing dry sunny slopes. Shelters are abandoned rodent burrows, cracks under stones, voids in rotten stumps. Avoids damp places and is very reluctant to go into the water. The food of copperheads consists mainly of lizards, although occasionally they can eat small mammals, bird chicks, small snakes and insects. The copperfish strangles adult lizards, wrapping them with the rings of its body so that only the head and tail of the victim protrude from the ball. Having strangled the prey, the snake gradually unfolds the rings of its body and begins to swallow it, usually from the side of the head. With large and strong lizards, the copperfish manages to cope far from always and not immediately. More often, however, the snake wins, which is helped a lot in this by the poisonous saliva for lizards that enters the blood of the prey. Small copperfish lizards, especially young individuals, are eaten alive, unmistakably grabbing them by the head.

    It is generally accepted that these snakes mate in the spring, shortly after waking up from hibernation. However, according to recent observations made in France, mating can also take place in autumn, and the spermatozoa are stored in a special seminal receptacle until spring, when the eggs are fertilized. Copperhead refers to ovoviviparous snakes: her eggs are so late in the mother's oviducts that the young hatch at the time of laying eggs. The number of cubs brought by one female varies from 2 to 15. They appear in late August or early September. The length of newborns is 13-15 cm. A characteristic feature of the copperhead is its ability to collect the body into a tight tight lump, inside which it hides its head. Often, instead of fleeing, the copperhead assumes the described posture and reacts to every touch only by a large contraction of its body. When disturbed, from time to time, with a short hiss, it throws the front third of the body towards the danger. A caught snake often bites violently, and especially large specimens are able to bite through the skin to the point of blood. In many places, these harmless snakes are considered very poisonous, unfairly persecuted and destroyed.

    Common viper. The common viper, as a rule, is of medium size - males reach 60 cm, females 70 cm. In the north of the range, rare specimens reach 1 meter in length. The head is separated from the body by a short neck, the muzzle from above, in front of the line connecting the anterior edges of the eyes, has 3 large shields (one in the middle and two on the sides), as well as a number of smaller ones. The pupil is vertical. The muzzle is rounded at the end. The nasal opening is cut in the middle of the nasal shield. Coloration varies greatly from gray and bluish to copper red and black, with a characteristic zigzag pattern on the back along the spine. In the latter case, the pattern is practically indistinguishable.

    An ordinary viper lives on average 11-12 years. It quickly adapts to any terrain and can live at altitudes up to 3000 meters above sea level. The distribution is uneven depending on the availability of wintering sites. Saddled, as a rule, does not move further than 50-100 meters. The exception is forced migration to the wintering place, in which case the snakes can move up to 5 km away. Wintering usually takes place from October-November to March-April (depending on the climate), for which he chooses a depression in the ground (burrows, crevices, etc.) at a depth of up to 2 meters, where the temperature does not fall below +2 - +4 °C In the event of a shortage of such places, several hundred individuals may accumulate in one place, which crawl out to the surface in spring, which creates the impression of great crowding. Subsequently, the snakes crawl away. In the summer, it often basks in the sun, the rest of the time it hides under old stumps, in crevices, etc. The snake is not aggressive, and when a person approaches, it tries to use its camouflage coloration as much as possible, or move away. Only in the event of a sudden appearance of a person or in the event of a provocation on his part, she can try to bite him. This cautious behavior is explained by the fact that it needs a lot of energy to reproduce the poison in conditions of changing temperatures. It feeds mainly on rodents, amphibians and lizards, although it occasionally eats birds and their eggs.

    The mating season is in May, and offspring appear in August or September, depending on the climate. Viviparous viviparous - eggs develop and cubs hatch in the womb. Usually up to 8-12 juveniles appear, depending on the length of the female. It happens that at the time of childbirth, the female wraps around a tree or stump, leaving her tail to a canopy, “scattering” babies on the ground, who from the first moment begin an independent life. Juveniles are usually 15-20 cm long and are already poisonous. Many believe that only born individuals are more poisonous, but this is not true. It is also not true that juveniles are more aggressive. As soon as they are born, snakes usually molt. In the future, molting of young and adults occurs 1 - 2 times a month. Before their first hibernation in October-November, they never eat, because before hibernation they must digest all the food they eat in order to avoid metabolic problems.

    The common viper is deadly poisonous, and its venom is similar to that of rattlesnakes. However, it produces a much smaller amount of poison compared to the latter, and for this reason is considered less dangerous. The bite is rarely fatal. However, the bitten person should seek immediate medical attention. The composition of the poison includes high-molecular proteases of hemorrhagic, hemocoagulative and necrotizing action and low-molecular neurotropic cytotoxins. As a result of a bite, hemorrhagic edema, necrosis and hemorrhagic impregnation of tissues in the area of ​​​​venom injection occur, accompanied by dizziness, lethargy, headache, nausea, and shortness of breath. In the future, progressive shock of complex genesis, acute anemia, intravascular coagulation, and increased capillary permeability develop. In severe cases, dystrophic changes occur in the liver and kidneys. In spring, viper venom is more toxic than in summer.