Reptile biology. Class Reptiles: general characteristics
In the sea and in the air. At the end of the Cretaceous, most of the reptiles became extinct. Modern reptiles are only scattered remnants of that world.
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In reptiles, both features of simpler amphibians and features of higher vertebrates are observed.
Cover
Muscular system
The brain is located inside the skull. Row important features distinguishes the brain of reptiles from the brain of amphibians. They often talk about the so-called sauropsid type of the brain, which is also inherent in birds, in contrast to the ichthyopsid type in fish and amphibians.
There are five divisions of the brain of reptiles.
- 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 rudiments of the neopallium. The fundus of the forebrain is mainly composed of striatum.
- The diencephalon is located between the forebrain and midbrain. The pineal gland is located in its upper part, and the pituitary gland is located on the lower side. In most lizards and tuataras (as well as many extinct forms), the parietal eye develops near the pineal gland, and in crocodiles, both of these organs are lost. The floor of the diencephalon is occupied by the optic nerves and their intersection (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 that of amphibians.
- The cerebellum covers the anterior part of the medulla oblongata. It is larger in comparison with the amphibian cerebellum.
- The medulla oblongata forms a bend in the vertical plane, which is characteristic of all amniotes.
12 pairs of cranial nerves branch off from the brain. V spinal cord the division into white and gray matter is more distinct than that of amphibians. Segmental spinal nerves extend from the spinal cord to form the 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 senses:
Respiratory system
For reptiles, suction-type breathing is characteristic by expanding and narrowing the chest with the help of the intercostal and abdominal muscles. Air trapped through the larynx enters the trachea - a long breathing tube, which at the end is divided into bronchi leading to the lungs. Like amphibians, reptile lungs have a sac-like structure, although their internal structure is much more complex. The inner walls of the pulmonary sacs have a folded cellular structure, which significantly increases the respiratory surface.
Since the body is covered with scales, skin respiration in reptiles is absent (with the exception of soft-bodied turtles and sea snakes), and the lungs are the only respiratory organ.
Circulatory system
Like amphibians, most reptiles have a three-chambered heart, consisting 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 blood oxygen is established in the slit space around the incomplete ventricular septum. After atrial contraction arterial blood from the left atrium is in the upper half of the ventricle and displaces the venous blood flowing from the right side of the ventricle into the lower half. On the right side of the ventricle, mixed blood... With the contraction of the ventricle, 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 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, reptiles have three independent vessels: the pulmonary artery and the right and left aortic arches. Each aortic arch folds back around the esophagus, and, converging with each other, they connect to the unpaired dorsal aorta. The dorsal aorta stretches backward, sending arteries along the way to all organs. From the right aortic arch, extending from the left arterial ventricle, the right and left carotid arteries branch off with a common trunk, while both subclavian arteries, carrying blood to the forelimbs, branch off from the right arch.
A complete separation into two independent circles of blood circulation in reptiles (including crocodiles) does not occur, since venous and arterial blood mix in the dorsal aorta.
Like fish and amphibians, all modern reptiles are cold-blooded animals. Despite this, many reptiles can adjust their temperature by moving from shade to the sun and back, or changing color, getting darker to keep warm, or lighter to cool off.
Digestive system
Due to the variety of food available for nutrition, the digestive tract in reptiles is much more differentiated than in amphibians.
The digestive system begins with the mouth opening, limited by jaws with conical, identical, firmly growing teeth (homodont system). The tongue is free, muscular in front, mobile, towards the end it becomes thinner and bifurcated. The oral cavity is delimited from the pharynx by the developing secondary bone palate. The multicellular salivary glands contain digestive enzymes. The pharynx passes into the narrow esophagus, then into the muscular stomach and intestines. The stomach has thick muscle walls. On the border between the small and large intestine there is a cecum, which amphibians do not have. A 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 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 connect to the cloaca through the ureters.
Thin-walled stem bladder connects to the cloaca with a thin neck on its ventral side. In some reptiles, the bladder is underdeveloped (crocodiles, snakes, some lizards).
Also, a new organ of excretion appears - the pelvic kidney.
In terrestrial reptiles, the end product of nitrogen metabolism is uric acid.
Reproductive system
Reptiles are dioecious animals, bisexual reproduction.
Reproductive system of males consists of a pair of testes, which are located on the sides lumbar spine. From each testis, a seed canal leaves, which flows into the Wolffian canal. With the appearance of a trunk kidney in wolf reptiles, the canal in males acts only as a vas deferens and is completely absent in females. The Wolf's canal opens into the cloaca, forming a seminal vesicle.
Reproductive system of females represented by the ovaries, which are suspended on the mesentery to the dorsal side of the body cavity along the sides of the spine. The oviducts (Müllerian canals) 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. For many representatives, care for offspring is characteristic, in particular, female crocodiles transfer offspring from the place of laying to reservoirs in oral cavity, although in some cases it can eat a cub.
Nutrition
Most reptiles are carnivores. For some (for example, agamas, iguanas) it is characteristic mixed food... There are also almost exclusively herbivorous reptiles (land turtles).
Movement
For most reptiles, crawling is a characteristic mode of movement. Many species swim well. Several genera are capable of gliding flight; actively flying reptiles are known only from fossil remains (see Pterosaurs).
Voice
Most reptiles do not have a real vocal apparatus and can only make the most primitive sounds like hiss or whistles. Their voices are monotonous.
Economic value
The value of reptiles for humans is relatively small. The leather 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 used for food. Some lizards and snakes can also be eaten. Snake venom is used in medicine. Many snakes are useful in exterminating rodents, and lizards are useful in exterminating insects. Some types of reptiles are kept as pets.
Poisonous snakes pose a great danger to humans, especially in tropical countries. Large crocodiles are dangerous to humans and damage livestock. Many turtles harm fisheries.
The origin of reptiles
The first representatives of reptiles - cotylosaurus - are known from the Middle Carboniferous. By the end of the period, animal-like reptiles appear, which in the Permian period settled practically over the entire land, becoming the dominant group among reptiles. In the Mesozoic era, reptiles flourish, among the representatives there is the greatest diversity. The development of sea and river reservoirs, as well as airspace is underway. In the Mesozoic, all groups of reptiles are formed. The last group- snakes - formed in the Cretaceous period.
At the end of the Cretaceous, there is a sharp decline in the number of reptile species. Unambiguously indicate the reasons for the extinction modern science not yet.
Phylogenetics
Amniota Reptilia Eureptilia Romeriida Paleothyris acadiana
Model objects
In 2011, the genome of a reptile - anolis karolinsky lizard - was decoded. So this reptile entered the circle
General characteristics of the Class Reptiles
Reptiles (reptiles - from Lat. Reptilia). There are 8,734 known species of reptiles 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 shingles. In turtles, fused scutes form a solid, durable shell. The change of the stratum corneum occurs by full or partial molting, which in many species occurs several times a year.
Dense and dry skin contains scent glands. The mucous glands are absent.
In the outer part of the inner layer of the skin, there are often special cells called chromatophores. In these cells, pigments are secreted: melanins and carotenoids. Also in chromatophores there is guanine capable of reflecting light. Thanks to chromatophores, some reptiles are able to change their body color for a relatively a short time... Chameleons are the most famous representatives with a similar property.
Skeletal system
In the axial skeleton of reptiles, the division into divisions 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 caudal (pars caudalis).
The following structure of the axial skeleton is typical for reptiles. The total number of vertebrae is different in different types(50-80, in snakes it grows to 140-435). From the vertebrae cervical(from 7 to 10) the two front 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 16 to 25 vertebrae, each with a pair of ribs. The first few vertebrae attach to the sternum, forming chest(absent in snakes). In the sacral region, there are only two vertebrae, to the wide transverse processes of which the pelvis is attached. The caudal section is made up of several tens (15-40) vertebrae gradually decreasing in size. The last caudal vertebrae are small, rod-shaped bones.
In some groups of reptiles, the axial skeleton is different. 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 region fuse with the dorsal shield of the shell, as a result of which they are immobile.
The skull of reptiles is much more ossified than that of amphibians. Only the olfactory capsule and the auditory region contain a small amount of cartilage. The axial and visceral parts of the skull are embryonically formed separately, but in adults they grow together into a single formation. The skull includes both cartilaginous (replacement, or primary) and numerous skin (integumentary, or secondary) bones.
The belt of the forelimbs is similar to the belt of amphibians, differing only more strong development ossification. The forelimb of a reptile consists of the shoulder, forearm and hand. Back - from the thigh, lower leg and foot. There are claws on the phalanges of the limbs.
Muscular system
The muscular system of reptiles is represented by the chewing, cervical muscles, muscles abdominal as well as flexor and extensor muscles. Characteristic of amniotes present intercostal muscles playing important role with the act of breathing. The subcutaneous musculature allows you to change the position of the horny scales.
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. They often talk about the so-called sauropsid type of the brain, which is also inherent in birds, in contrast to the ichthyopsid type in fish and amphibians.
There are five divisions 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 rudiments of the neopallium. The fundus of the forebrain is mainly composed of 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 floor of the diencephalon is occupied by the optic nerves and their intersection (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 that of amphibians.
* The cerebellum covers the anterior part of the medulla oblongata. It is larger in comparison with the amphibian cerebellum.
* The medulla oblongata forms a bend in the vertical plane, which is characteristic of all amniotes.
12 pairs of cranial nerves branch off from the brain. In the spinal cord, the division into white and gray matter is more distinct than in amphibians. Segmental spinal nerves extend from the spinal cord to form the 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 senses:
* The organ of vision - the eyes, are more complex than that of frogs: there is a ring of thin bone plates in the sclera; from back wall an outgrowth departs of the eyeball - a ridge protruding into the vitreous; in the ciliary body, the striated muscles are developed, which allows not only to move the lens, but also to change its shape, thus making focusing in the process of accommodation. The organs of vision have adaptations to the work of the air environment. The lacrimal glands prevent the eyes from drying out. The outer eyelids and blinking membrane perform protective function... In snakes and some lizards, the eyelids grow together to form a transparent shell. The retina of the eye can contain both rods and cones. Nocturnal species have no cones. In most daytime species, the range of color vision is shifted to the yellow-orange part of the spectrum. Vision is critical among the senses of reptiles.
* The organ of smell is represented by the internal nostrils - the choans and the vomeronasal organ. Compared to the structure of amphibians, choanas 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 under the surface of the sand at a depth of 6-8 cm.
* Taste organ - 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. It is especially developed in snakes. In pit-headed snakes, thermal radars can even 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 bone - 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 that propagate 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 (in crocodiles, 100-3000 Hz).
* Tactile sensation is pronounced, especially in turtles, which can even feel a light touch on the shell.
For reptiles, suction-type breathing is characteristic by expanding and narrowing the chest with the help of the intercostal and abdominal muscles. Air that has entered through the larynx enters the trachea - a long respiratory tube, which at the end is divided into bronchi leading to the lungs. Like amphibians, reptile lungs have a sac-like structure, although their internal structure is much more complex. The inner walls of the pulmonary sacs have a folded cellular structure, which significantly increases the respiratory surface.
Since the body is covered with scales, skin respiration in reptiles is absent (with the exception of 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 blood oxygen is established in the slit space around the incomplete ventricular septum. After atrial contraction, arterial blood from the left atrium enters the upper half of the ventricle and displaces the venous blood flowing 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 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, reptiles have three independent vessels: pulmonary artery, and the right and left aortic arch. Each aortic arch folds back around the esophagus, and, converging with each other, they connect to the unpaired dorsal aorta. The dorsal aorta stretches backward, sending arteries along the way to all organs. From the right aortic arch, extending from the left arterial ventricle, the right and left carotid arteries branch off with a common trunk, while both subclavian arteries, which carry blood to the forelimbs, branch off from the right arch.
A complete separation into two independent circles of blood circulation in reptiles (including crocodiles) does not occur, since venous and arterial blood mix in the dorsal aorta.
Like fish and amphibians, all reptiles are cold-blooded animals.
Digestive system
Due to the variety of food available for nutrition digestive tract in reptiles it is much more differentiated than in amphibians.
The stomach has thick muscle walls. On the border between the small and large intestine there is a cecum, which amphibians do not have. A large reptile liver has gall bladder... The pancreas in the form of a long dense body lies in a loop duodenum... The intestine ends with a cloaca.
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 connect to the cloaca through the ureters.
The thin-walled stem 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.
Mens reproductive system consists of a pair of testes, which are located on the sides of the lumbar spine. From each testis, a seed canal leaves, which flows into the Wolffian canal. With the appearance of a trunk kidney in wolf reptiles, the canal in males acts only as a vas deferens and is completely absent in females. The Wolf's canal opens into the cloaca, forming a 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 along the sides of the spine. The oviducts (Müllerian canals) are also suspended on the mesentery. In the front 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 its dorsal side.
Development:
Fertilization is internal. The development of the embryo takes place in the egg. Reptiles have direct postembryonic development.
Most reptiles are carnivores. For some (for example, agamas, iguanas), a mixed diet is characteristic. There are also almost exclusively herbivorous reptiles (land turtles).
Most reptiles do not have a real vocal apparatus and can only make the most primitive sounds like hiss or whistles. Their voices are monotonous.
Reptiles of the Vladimir region
It has a long, fusiform body. Young spindles on top of a very beautiful silvery-white or light cream color with two closely approximated thin dark lines running along the ridge, starting from a more or less triangular spot located at the back of the head. The sides of the body and the belly are black-brown or almost black, and the border between the light dorsal and dark lateral coloration of the body 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 lighten noticeably, but usually remain darker than the back. blue spots... In length, this lizard reaches 60 cm, more than half of which falls on a very brittle tail, slightly sharpened at the end.
Lifestyle. Lives in deciduous and mixed forests, also found in bushes, meadows, fields and gardens, but usually not far from the forest. She hides in rotten stumps, under fallen tree trunks, in heaps of dead wood, in the thickness of the forest floor, under stones and in anthills. Often, the spindle makes a hole for itself, driving 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, writhing serpentinely with her whole body. In the spring, for the first time after wintering, the spindles are basking in the sun for a long time and are not uncommon in the places where they live. However, already from mid-June, and much earlier in the south, these lizards switch to a twilight and nocturnal lifestyle and leave their shelters in daytime very rarely, usually in cloudy but warm weather or after heavy night rain. Spindles feed on earthworms, terrestrial molluscs, insect larvae, millipedes 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 seizes it slowly. Sharp, bent back teeth reliably hold slippery wriggling worms and naked slugs in the mouth, which the lizard slowly swallows, alternately tilting its head to one side or the other. If the captured worm firmly clings to the soil in the earthen burrow with the rear end of the body, the spindle, stretching in length, begins to quickly rotate in one direction, thus tearing off part of the prey. They do the same when two of them grab one long worm or slug and, rotating in different sides, quickly twist the prey in half. Eating snails, the spindle gradually rests more and more with its head 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 occurs in spring, the female gives birth to 5 to 26 cubs, which are born in a transparent facial shell, which they immediately tear and creep to the sides. The length of young lizards immediately after birth does not usually exceed 100 mm, including the tail. Spindles hibernate in the holes of rodents, 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 fragile tail that remains in the teeth or claws of the predator helps it to escape. In many places, the spindle is considered poisonous and, mistaken for a snake, is ruthlessly exterminated. In reality, the spindle is completely harmless and only benefits a person, in many ways it destroys various pests. Like the yellow jellyfish, this lizard tolerates captivity very well and quickly gets used to humans. There are cases when she survived in captivity for 20-30 and even 50 years.
The lizard is quick. Young lizards of this species are brownish-gray or brownish on top with three light narrow, edged black stripes, the middle one stretches along the ridge, and both lateral ones pass along the sides of the back and are lost on the tail. On the sides of the body, usually small white eyes are located in one row. This coloring changes with age. Light trunk stripes blur and become less clear, and along the ridge separate irregular shape dark brown or completely black spots, 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 salad, olive or green coloring, 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 one-color 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 refers to green males. In length, the lizards do not exceed 25 - 28 cm with their tail.
The nimble lizard prefers dry and sunny areas everywhere, inhabiting 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 nimble lizard is noticeably inferior to the green and striped, nevertheless, justifying its name, it runs so fast that it is rather 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 pursuit, this lizard unexpectedly abruptly moves its tail to the side during the whole move and, “making a half-turn on the spot, turns its head towards the pursuer. Performing this maneuver and with surprising speed changing the direction of running several times in a row, the animal often completely confuses the pursuer. Often the lizard escapes in the trees, and, like a squirrel, it rises in a helical manner along the trunk. When caught, she strenuously breaks out, opens her mouth wide and, on occasion, can grasp the finger quite strongly. In the middle lane, nimble lizards wake up in the 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 old ones. From early morning, as soon as the sun warms the ground a little, the lizards come out of their holes and warm themselves 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 is alert, watches it with its eyes for some time, and then quickly darts off and grabs it. At first she flutters large grasshoppers and beetles in her mouth for a long time, releasing from time to time to the ground and then grabbing them again. At the same time, she tears off their hard chitinous parts - the elytra and legs, and then already swallows the rest whole. Having swallowed the prey, it carefully licks itself 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 afar, hearing the characteristic buzz of a bee returning with a bribe, the lizard is alert, raises its head and then, with a quick and precise movement, jumping upwards, often seizes the insect even before it descends on the entrance. However, the harm caused in this way certainly pays off with the benefits from the destruction of a large number of pests of agriculture and forestry... The lizard, fed up as a result of the morning hunt, again settles in the sun, changing its place from time to time and moving away from the approaching shadow. When its body is very hot by the sun, the lizard lies down on its belly, lifts its legs and tail and, shaking its head, quickly opens and closes its mouth. In such a tense state, she usually remains only 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, after several unsuccessful attempts, grabs her by the tail. The female immediately stops, and her tail begins to wriggle rapidly. Further, the male, without releasing his tail from 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 alone sharp movement bends the body, and mating occurs. When meeting each other, the males immediately rise on their outstretched front legs, strongly squeeze the front part of the body from the sides, and slowly begin to approach each other sideways. Sometimes one of them, obviously weaker, breaks down and takes flight. However, more often fierce fights occur between males. Each opponent tries to grab the opponent by the neck or 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 usually lies on his back only for a few moments, the next second he gets to his feet and swiftly flees, and the winner, not content with the victory he has won, starts to chase him. However, more often battles between males end in the fact that one of them falls open jaw into the mouth of the other and both of them are in complete frenzy with closed eyes roll on the ground until at last the weaker one breaks free and runs away. mating season adult lizards split into pairs and settle together in one burrow, in the vicinity of which they hunt and bask in the sun together. 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 burrow. Young ones appear from the end of July. Lizards usually hibernate in summer burrows, the entrance to which is clogged with leaves and earth. In the middle lane, adults usually hibernate at the beginning of September.The fast lizard tolerates captivity very well, quickly gets used to humans and begins to take food from its 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 lightens, 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 dark relatively wide stripes on the sides of the body. In addition, small dark specks are scattered throughout the body in disarray. The underside of adult males is orange or brick-red, whitish-gray, yellowish or greenish in females. 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, which is somewhat thickened at the base in males. Unlike most other true lizards, the females of this species are superior in size to the males.
Lifestyle. In most of its vast range, the viviparous lizard adheres to humid habitats, meeting in forested areas of bogs, peat bogs, overgrown clearings, forest edges and clearings, in deciduous and coniferous forest nurseries, on the banks of streams and canals overgrown with shrub vegetation, and in similar places. On forest clearings and edges, lizards most willingly settle at individual stumps, fallen trees, at the base of bushes and between tree roots. They do not dig their own burrows and use the burrows of rodents or the spaces under peeled bark on stumps and dry trees for shelter; in the mountains they hide under stones. 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 the spring, the viviparous lizard wakes up from hibernation quite early, when there are still separate 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 have settled here climb 1-2 m up the trunk, where they hunt for insects. At the end of the day, several lizards can sometimes be observed on the illuminated side of the trunk. Viviparous lizards feed on various insects, spiders, mollusks, worms, catching them not only on the ground, but also on herbaceous plants and tree trunks. Mating occurs shortly after awakening in April - May. Unlike all other species of its kind, this lizard gives birth to live cubs. Gestation lasts about 90 days, and juveniles (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 next year... “Before the onset of labor,” writes A. M. Nikolsky, “the female becomes restless, scratches the ground, bends her tail over her back ... and finally, in the evening, will give birth to the first cub, usually still sitting in the facial shell; two minutes later, the second is born, and so on. After each clutch, she takes several 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 up and down and does not show any concern for her children. Sometimes she returns to the place of laying, but only to eat part of the facial membranes. The first days of their lives, the cubs sit in the cracks of the earth, curled up their tail, and do not go out in search of food. "
Already ordinary. The most famous and widespread species of the genus. It differs well 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 have a crescent shape and are fringed with black stripes in front and behind. Sometimes there are individuals in which light spots weak 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, but midline the abdomen stretches an uneven black stripe, which in some individuals is so expanded that it displaces almost the entire White color, remaining only in the throat. The body length of a snake can reach 1.5 m, but usually does not exceed 1 m; females are noticeably larger than males.
The habitats of the snake are very diverse, but they are certainly quite humid. Snakes are especially numerous along the banks of calm rivers, lakes, ponds, grassy swamps, in humid forests and bush-covered floodplain meadows, but sometimes they are even found in the open steppe and in the mountains. They often live in vegetable gardens, orchards, in barnyards and sometimes crawl into various outbuildings. In spring, as well as in autumn, when the soil stores a lot of moisture, snakes can go far from the water. The shelters of snakes are hollows under the roots of trees, heaps of stones, holes of rodents, haystacks, cracks 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, mobile snakes. They crawl quickly, can climb trees and swim excellently 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 head above the surface of the water and leaving behind a characteristic ripple, therefore, snakes moving along the pond are clearly visible. Snakes are active during daylight hours, and at night they hide in shelters. 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 the 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 on the bottom for a long time. 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-coated eggs in one portion, which often stick together like a rosary. Eggs die easily from drying out, so snakes lay them in moist, but heat-retaining (25-30 °) shelters: under fallen leaves, in damp moss, heaps of manure and even garbage dumps, abandoned burrows of rodents, rotten stumps. Sometimes, especially with a lack of suitable shelters, several females lay eggs in one place. A case is described when over 1200 eggs of snakes were found under an old door lying in a forest clearing, arranged in several layers. Initial stages the development of the snake embryo still takes place in the mother's body, and in the newly laid eggs, the pulsation of the embryo's heart is noticeable with the naked eye. Incubation lasts about 5-8 weeks. Young snakes at the moment of emergence from eggs are about 15 cm long; they immediately creep apart and begin to lead an independent lifestyle. Young people lead a much more secretive lifestyle than adults and are relatively rare to see. For the winter, snakes take refuge in deep holes of rodents, in the cracks of coastal cliffs, under the roots of rotten trees. Sometimes they hibernate one by one, 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. V warm days snakes begin to crawl out of their winter shelters and bask for a long time near them in the sun, sometimes gathering in balls of many individuals together. With each spring day, the snakes become more active and gradually creep away from their wintering places.
Snakes feed on small frogs, toads and their juveniles. Occasionally, lizards, small birds and their chicks, as well as small mammals, including newborn baby water rats and muskrats, become their prey. Young snakes often catch insects. The widespread belief that snakes feed on fish and are very harmful to fish farming is based on a misunderstanding. Small fish are rarely eaten by these snakes and in small quantities... Even in fish-rich reservoirs, snakes sometimes swim among such dense schools of fry that they literally push them apart with their body, and nevertheless, in the stomachs of the caught snakes, it was possible to find not fish, but only young frogs. In one hunt, a large one can swallow up to 8 frogs or large tadpoles of a marsh frog. The frogs that are being chased 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 utter a cry, completely unlike the sounds that we are used to hearing from them. This cry is more like the plaintive 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. As a rule, he already tries to grab the frog by the head, but often he does not succeed, and he grabs it by the hind legs and begins to slowly draw it into his mouth. The frog beats hard and makes croaking sounds. It already swallows small frogs easily, but sometimes it spends several hours devouring large individuals. If danger is already threatening, then it usually belches, like other snakes, the swallowed prey, and it opens its mouth very wide if the swallowed animal was large. Cases were observed that snakes regurgitated live frogs, which, despite the fact that they had been in the snake's throat, turned out to be quite viable in the future. Like all snakes, snakes are capable of long time go without food. There is a known case when a snake without harm to itself starved for more than 300 days. They drink snakes, especially on hot days, a lot. Snakes have a lot of enemies. They are eaten by snake 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. Snakes always try to hide from a person by flight. Unable to crawl away, sometimes they (especially large individuals) take a threatening pose: they curl up in a ball and from time to time throw their head forward with a loud hiss. Once caught, they bite, but only in extremely rare cases, causing light, quickly healing scratches with their teeth. The only remedy for snakes is the extremely smelly yellowish-white liquid they release from their cloaca. In many cases, the caught snake quickly stops resistance, throws prey out of the stomach if it has been eaten recently, and then completely relaxes the body, opens its mouth wide and, with its tongue out, hangs lifelessly in its hands or rolls over onto its back. This state of "imaginary death" quickly disappears if you throw the snake into the water or just leave it alone. Snakes live well in captivity, they quickly begin to take the food offered to them and soon become completely tame. They need water for drinking and bathing.
Copperhead ordinary. The length of the body is up to 65 cm. The coloration of the back varies from gray, gray-brown and yellowish-brown to red-brown and copper-red. Reddish tones especially characteristic of males. Along the back in 2-4 longitudinal rows, small dark spots, which in some specimens almost merge with each other and are clearly visible, while in others, on the contrary, they are poorly expressed. On the neck there are two brown or black-brown stripes (or two spots), usually merging at the back of the head. The head is dark dorsally or with a characteristic pattern of an arcuate stripe cut in front of the eyes 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 underparts are gray, steel-bluish, brownish, orange-brown, pink or almost red, usually with dark blurred spots or specks.
It is found most often in dry hilly areas among thickets of bushes and on forest edges, but can also be found in continuous forests, in meadows and even in the steppe. It rises into the mountains to an altitude of 3000 m, choosing dry sunny slopes. Abandoned rodent burrows, cracks under stones, voids in rotten stumps serve as shelters. Avoids damp places and is very reluctant to go into the water. Copperheads' food consists mainly of lizards, although occasionally they can eat small mammals, bird chicks, small snakes and insects. Copperhead strangles adult lizards, wrapping them in rings of its body so that only the head and tail of the victim protrude from the ball. Having strangled prey, the snake gradually dissolves the rings of its body and begins to swallow it, usually from the side of the head. Copperhead does not always manage to cope with large and strong lizards, and not immediately. More often, however, the snake wins, which is helped a lot in this by the saliva poisonous for lizards, which gets into the blood of the prey. Copperhead 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 awakening from hibernation. However, according to observations recent years made in France, mating can take place in the fall, and the sperm are stored in a special seminal receptacle until spring, when eggs are fertilized. Copperhead refers to ovoviviparous snakes: its eggs are so retained in the mother's oviducts that the young hatch at the time of oviposition. 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. Characteristic feature Copperhead is its ability to collect the body in 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 with a large squeeze of its body. Alarmed, she from time to time, with a short hiss, throws the front third of the body in the direction of danger. A caught snake often bites violently, and especially large specimens are able to bite through the skin to 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 torso short neck, muzzle from above, in front of the line connecting the anterior edges of the eyes, has 3 large scutes (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. The coloration varies greatly from gray and bluish to copper-red and black, with a characteristic zigzag pattern on the back along the ridge. 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 up to 3000 meters above sea level. Distribution is uneven, depending on the availability of suitable wintering sites. The saddles usually do not move further than 50-100 meters. The exception is forced migration to the wintering place, in this case the snakes can move away to a distance of up to 5 km. Wintering usually occurs from October-November to March-April (depending on the climate), for which it chooses a deepening in the ground (holes, crevices, etc.) at a depth of up to 2 meters, where the temperature does not drop below +2 - +4 ° C. In the event of a shortage of such places, several hundred individuals can accumulate in one place, which in spring crawl out to the surface, which creates the impression of great crowding. Subsequently, the snakes sprawl. V summer time often heats himself 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 color as much as possible, or to move away. Only in case of an unexpected appearance of a person or in case of provocation on his part, she can try to bite him. This cautious behavior is explained by the fact that it requires a lot of energy to reproduce poison in conditions of changing temperatures. It feeds mainly on rodents, amphibians and lizards, although sometimes it eats birds and their eggs.
Mating season is in May, and offspring hatch in August or September, depending on the climate. Viviparous viper - 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 overhanging, "scattering" babies on the ground, which from the first moment begin independent life... Juveniles are usually 15-20 cm long and are already poisonous. Many people believe that only born individuals are more poisonous, but this is not true. It is also not true that juveniles are more aggressive. Once born, snakes usually molt. In the future, molt of young and adults occurs 1 - 2 times a month. Before their first hibernation in October-November, they never feed, since 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 much less poison than the latter, and for this reason it is considered less dangerous. The bite is rarely fatal. However, the bitten person must immediately seek medical help... The poison contains high molecular weight proteases of hemorrhagic, hemocoagulating and necrotizing action and low molecular weight neurotropic cytotoxins. As a result of the bite, hemorrhagic edema, necrosis and hemorrhagic tissue permeation occur in the zone of injection of the poison, accompanied by dizziness, lethargy, headache, nausea, and shortness of breath. In the future, progressive shock of complex genesis, acute anemia, intravascular blood 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.
Reptiles are very interesting and very unusual creatures. The general characteristics of these creatures are very detailed. Not surprisingly, this class of chordate land animals includes snakes, lizards, amphisbens, beakheads, crocodiles, and turtles. They all 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 come from? A general description always begins with information about it. It is logical, because everyone should know that land animals belonging to this class are distant descendants of dinosaurs that dominated the Mesozoic era for more than 160 million years. As you know, they became extinct about 66 million years ago. Modern reptiles can only be compared with the scattered remains 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 found out that the adaptations that determined the evolution of birds were observed in their ancestors - representatives special forms reptiles. They were characterized by warm-bloodedness, a developed brain and an insulating body covering (feathers).
Cover
Now - a little more details about the anatomical specifics inherent in such creatures as reptiles. The general characteristic states that they have the traits of both amphibians and higher. 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 external stimuli and moisture loss.
And the scales also help snakes to move. Due to the presence of plates, animals push off from uneven ground and move in one direction or another.
Reptile covers are different. In some creatures, the scales fit tightly to each other. For others, they seem to overlap. For some, they even transform into ridges or spines, due to which the creatures are protected from predators.
But one of the most interesting covers can be observed in the Moloch lizard (Latin Moloch horridus). She is also called the "prickly devil". Looking at the photo above, you can see why exactly. This small lizard living in the deserts of Australia has a wide and flattened body, covered with innumerable short curved horny spines of various sizes. Above the eyes and on the cushion-shaped outgrowth on the neck, they form what resembles horns. This golden brown lizard is able to change its color depending on the light, temperature and its physiological state.
But it's worth getting back to the topic of the cover. Does it interfere with the growth of reptiles? No, because they periodically shed their old skin. And in the process of molting, their growth occurs. And the new cover is elastic and soft. Its keratinization takes time, and during this period these creatures hide because they are vulnerable without protection.
Skeletal structure
It is also important to mention it when it comes to what anatomical features have reptiles. The general characteristics are very interesting, because the total number of vertebrae can reach several hundred! In an adult (lat. Eunectes murinus), for example, there are about 435 of them! This is impressive. But if you 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 divisions is much more pronounced than in the case of amphibians. Five vertebral divisions are clearly distinguished: cervical, trunk, lumbar, sacral and caudal. The last of the listed maximum amount notorious vertebrae. They have very interesting building: the closer to the tail, the smaller their size. The last vertebrae are altogether 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 sternum. And the vertebrae of the torso of turtles do fuse with the shield of the shell, because of which they lose their mobility.
Scull
Also general characteristics reptiles can tell a lot about the structure of the skull of these creatures. Especially about the snake one. Its structure has evolved depending on the methods of obtaining food and the nature of the diet.
In amphibians, for example, a short and wide skull has elongated jaws that form a very long snout. The structure of the mouth allows these creatures to capture small prey when it attacks.
But in reptiles, the capture of prey is directly related to the pursuit of the victim. And the elongated snout has significant advantages here. 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 palatal processes form the secondary bony palate, which divides their oral cavity into the lower and upper sections. Therefore, they can breathe only by putting the end of the head with the nostrils out of the water, because the choanas (internal nasal openings) are shifted back, closer to the larynx.
Muscular system
Her description also includes the general characteristics of reptiles. The muscular system of these creatures is differentiated, represented by segmental muscles. Distinctive feature of these creatures - the intercostal muscles that perform the most important functions in the exercise of breathing.
The subcutaneous muscles are of particular interest. In some representatives, it is so strongly developed that it allows creatures to change the position of the scales. This, by the way, has already been mentioned in the section on the cover.
The role of energy "feeding" for the muscles of these creatures is played by 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 the active accumulation of lactic acid in the muscles will begin, the excess of which leads to fatigue. Therefore, representatives of this class, having made several dashes, they hide to rest. In a few hours, lactic acid breaks down, and the animal's strength is restored.
Snake musculature
It is necessary to tell about it separately. The general characteristics of the order of reptiles cannot convey all of its specificity. The fact is that the muscles of the snake are used to move the food it has swallowed inward, and not just to move.
It is also important to know that there are four main types of movement. The most famous is called serpentine, side 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 (Latin Dendroaspis polylepis) living in Africa. Its average speed is 11 km / h.
There is also a rectilinear method of movement (“caterpillar” technique). The snakes move forward on the skin of the abdomen, after which they tighten the entire back part body. In the third method, called parallel, the animal seems to throw itself aside (lateral cycle of movement). To see this is a rarity. This method characteristic of snakes living on loose sand in deserts.
The fourth method is no less rare. It is called “concertina. Or, in other words, the "accordion" technique. Used when moving the snake through the tree. Looks unusual, because the body seems to be going to form horizontal hinges, 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 roughly understand what it is “from the inside”, but after observing the movements described above, you can imagine everything visually.
Nervous system
It is also important to mention her when talking about the Reptiles 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, which consists 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 pineal gland. It is next to it, by the way, that the tuatara (the only modern representative of the beak-headed order) and lizards develop an unpaired photosensitive organ called the parietal eye. And crocodiles, by the way, have neither the pituitary gland nor the pineal gland.
The third section is called the middle one. It is represented by visual lobes. In this regard, the Reptiles class also distinguished itself. The general characteristic makes it possible to understand that their middle department and the visual cortex is much more developed than that of amphibians. The last part of the brain is the cerebellum. And also an oblong section.
However, this is not all there is to know about the Reptiles class. General characteristics, in short, makes it clear that representatives of this category of animals are distinguished by 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 noticeable, in contrast to 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 the general description of reptiles (or reptiles) will be incomplete without mentioning it.
So, these beings have six senses. The first is vision. Interestingly, many lizards are excellent at distinguishing colors. Shades - essential tool their communication. They recognize poisonous insects by color. And giant turtles are also color-sensing. 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. Pupils, by the way, are different in reptiles. For representatives leading a nocturnal or crepuscular lifestyle, it is vertical. And in geckos, on the narrowed pupils, you can even notice pinpoint holes that focus an independent image on the retina. This feature provides the maximum sharpness displayed for the lizard of reality.
As for the sense of smell. Its specificity can also be told by the general characteristics of reptiles. In short, the main role chemoreceptors play in the sense of smell of these creatures. Due to them, these animals perceive smell very well. They are able to find food buried at a depth of 8 centimeters. Vipers, snakes and monitor lizards, due to their sense of smell, can determine the type of 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 "designate" the occupied territory. These creatures mark their sites with an odorous substance.
Lifestyle
The general characteristics of reptiles can also tell about him. Grade 7 - about this stage v high school this topic is being studied.
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.
Reproduction 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 while in the egg, which is covered with either a calcareous or leathery shell. Ovoviviparity also occurs. Very rarely, cubs are born, like in viviparous animals. It is worth noting that caring for the offspring of these creatures is inherent. Female crocodiles, for example, carefully transfer their babies in the oral cavity from the clutch to the reservoirs.
It is also interesting to know that the vast majority of reptiles do not have a vocal apparatus. They cannot emit anything but whistle or hiss. So no marriage cries can be heard - these creatures are guided by the smell. Only eublefar lizards are able to squeak.
Well, the general characteristics and features were considered above. external structure reptiles. Finally, you can talk about some rare representatives.
The smallest creature of this class is one that lives in deserts and semi-deserts. You can also find it in areas where the Volga flows. it amazing creature covered with granular scales. Its body length reaches only 41 mm! It has about the same tail, which is easily discarded.
Also noteworthy is the gyurza, which is the largest representative a kind of giant vipers. It is a poisonous creature weighing 3 kilograms, the length of which reaches 2 meters.
Nose king cobra of course, gyurza cannot be compared. After all, this is the largest poisonous snake. Some individuals reach a length of 5.6 m. By the way, they grow throughout their life. And they live up to 30 years.
A snake like Taipan McCoy is very attractive. But a beautiful creature with golden-black scales is very dangerous. After all, it is the most venomous 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 not all the amazing creatures that the Reptiles (or Reptiles) class abounds in. The general characteristic allows us to understand how great their diversity is. But it is also worth noting the attention of the Far Eastern skink. It is a lizard that can be found in Japan or the Kuril Islands. She, like all the previously listed species, is listed in the Red Book of Russia. And its highlight is its amazing color, which can be appreciated by looking at the photo provided above.
Well, we can talk about this for a long time. After all, the world knows 9400 species of reptiles, and each of them is unique in its own way. But you can get acquainted with them individually. Everything that has been said above may well awaken interest in this.
Reptile class, or reptiles , has about 6 thousand species. These are real land animals.
Their development and flowering are associated with a change in the Paleozoic and especially in the Mesozoic era climatic conditions, a decrease in the number of wetlands, a general warming of the climate. The origin of reptiles is due to the following aromorphoses :
- the emergence of protective shells around the egg;
- internal fertilization;
- direct development;
- the appearance of cellular lungs with developed respiratory tract;
- the emergence of a partial, and in crocodiles a complete septum in the ventricle of the heart, which led to a partial separation of the flows of venous and arterial blood.
Changes such as internal fertilization, an increase in the anterior part of the brain and the appearance of a primary cortex in it were also important for life on land.
The reptile class has 4 modern orders: Scaly (lizards, snakes), Turtles, Crocodiles, Beakheads (tuatara).
External structure.Body reptiles are divided into sections - head, trunk, tail and two pairs of limbs. There are senses - sight, hearing, smell, taste, touch. The body is flattened in vertical direction and snuggles to the ground.
Skin integument formed by keratinized epidermis, renewed by their lower layers, consisting of living cells. Horny shields prevent moisture evaporation and desiccation. Moisture evaporates through the skin, but in desert animals this water loss is minimal. There are almost no skin glands. Reptiles grow during periodic molt.
Skeleton almost completely bony. Cartilage in the olfactory and auditory regions is preserved in the skull. There are two sections in the skeleton of the head - cerebral and visceral (facial). Spine consists of the following departments:
- cervical consists of 8 vertebrae in lizards. The first and second vertebrae (atlas and epistrophy) serve for the movable connection of the skull with vertebral column;
- lumbar-thoracic - from 16 to 25 vertebrae, each of which carries an edge. The first five pairs form the chest, fused with the sternum;
- sacral - 2 vertebrae, to which the pelvic bones are attached, forming the pelvic girdle;
- caudal - sometimes several tens of vertebrae.
Skeleton of the girdle of the forelimbs formed by paired clavicles, shoulder blades and coracoids. The belt of the forelimbs is stronger than that of amphibians. Free front limbs are similar in structure to the limbs of amphibians. Some representatives of the class have no limbs (snakes, legless lizards).
Pelvic girdle formed by paired, fused sciatic, iliac and pubic bones. Free hind limbs have a characteristic structure for terrestrial animals.
In the muscular system intercostal muscles appear, participating in respiration.
V digestive system as features should be noted conical teeth fused with bones, a long, muscular tongue, the presence of a rudimentary cecum.
Respiratory system pulmonary type with developed airways - larynx, trachea, bronchi. The increase in the respiratory surface area led to a more complete oxidation of the blood. Respiratory rate in reptiles depends on temperature environment... The higher it is, the more often the animal breathes.
Circulatory system closed. Two circles of blood circulation. The heart of most representatives is three-chambered, while in crocodiles it is four-chambered. Reptiles are cold-blooded animals, with relatively low level metabolism, because mixed blood is supplied to 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 the 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 fluid.
Sense organs developed and adapted to terrestrial existence. The eyes have eyelids and nictitating membrane; the organ of hearing consists of the inner and middle ear. There is only one bone in the middle ear. In inner ear the snail 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. They destroy insects by feeding on rodents, regulate their numbers; eaten, leather and shells are used to make various products; snake venom is used in pharmacology.