Are snakes really deaf? The vision of snakes Why can't a snake see behind transparent glass?

Reptile eyes indicate their way of life. U different types We observe a peculiar structure of the organs of vision. To protect their eyes, some “cry”, others have eyelids, and still others “wear glasses”.
Reptile vision , like the diversity of species, is very different. How the eyes are positioned on a reptile's head largely determines how much the animal sees. When the eyes are set on both sides of the head, the visual fields of the eyes do not overlap. Such animals see well everything that happens on both sides of them, but their spatial vision is very limited (they cannot see the same object with both eyes). When a reptile's eyes are set at the front of its head, the animal can see the same object with both eyes. This position of the eyes helps reptiles more accurately determine the location of prey and the distance to it. IN land turtles and many lizards have eyes set on both sides of their heads, so they can clearly see everything that surrounds them. The snapping turtle has excellent spatial vision because its eyes are set at the front of its head. Chameleons' eyes, like cannons in defensive towers, can rotate independently 180° horizontally and 90° vertically - they can see behind them.

How do snakes exhibit their heat source?.
The most important sensory organ of a snake is the tongue in combination with Jacobson's organ. However, reptiles also have other adaptations necessary for successful hunting. To identify prey, snakes need more than just their eyes. Some snakes can sense heat emitted by the animal's body.
Pit-headed snakes, which include the true pit snakes, got their name due to the fact that they have a paired sensory organ in the form of facial pits located between the nostrils and the eye. With the help of this organ, snakes can sense warm-blooded animals by the difference in body temperature and external environment with an accuracy of 0.2 ° C. The size of this organ is only a few millimeters, but it can detect infrared rays emitted by potential prey and transmit the received information through nerve endings to the brain. The brain perceives this information and analyzes it, so the snake has a clear idea of ​​what kind of prey it encountered on its way and where exactly it is located. Different kinds reptiles are seen and perceived very differently the world. The field of vision, its expressiveness and the ability to distinguish colors depend on how the animal’s eyes are set, on the shape of the pupils, as well as on the number and type of light-sensitive cells. In reptiles, vision is also related to their lifestyle.
Color vision
Many of the lizards can perfectly distinguish colors, which is an important means of communication for them. Some of them recognize scarlet poisonous insects against a black background. In the retina of the eyes of diurnal lizards there are special elements of color vision - bulbs. Giant tortoises are color-sensitive, and some respond particularly well to red light. They are even thought to be able to see infrared light, which the human eye cannot distinguish. Crocodiles and snakes are color blind.
American night lizards react not only to shape, but also to color. However, their retina still contains more rods than cones.
Reptile vision
The class of reptiles, or reptiles, includes crocodiles, alligators, turtles, snakes, geckos and lizards such as the hatteria. The reptile needs to receive accurate information about the size and color of its potential prey. In addition, the reptile must detect and quickly react when other animals approach and determine who it is - a potential partner, a young animal of the same species, or an enemy that may attack it. Reptiles that live underground or in water have rather small eyes. Those of them that live on earth depend more on visual acuity. The eyes of these animals are structured in the same way as human eyes. Their very part is the eyeball with the optic nerve. In front of it is the cornea, which allows light to pass through. The cornea is the iris. At its center is the pupil, which contracts or dilates, allowing a certain amount of light to pass onto the retina. Under the pupil there is a lens through which rays hit the light-sensitive back wall of the eyeball - the retina. The retina is made up of layers of light- and color-sensitive cells connected by the optic nerves to the brain, where all signals are sent and where an image of an object is created.
Eye protection
Some species of reptiles use eyelids to protect their eyes, just like mammals. However, reptile eyelids differ from mammalian eyelids in that the lower eyelid is larger and more mobile than the upper.
The snake's gaze appears glassy because its eyes are covered with a transparent film formed by the fused upper and lower eyelids. This protective coating is a kind of “glasses”. During molting, this film comes off along with the skin. Lizards also wear “glasses,” but only some. Geckos do not have eyelids. To clean their eyes, they use their tongue, sticking it out of their mouth and licking the eye shell. Other reptiles have a "parietal eye". This is a light spot on the head of a reptile; like a regular eye, it can perceive certain light stimuli and transmit signals to the brain. Some reptiles protect their eyes from pollution using lacrimal glands. When sand or other debris gets into the eyes of such reptiles, the lacrimal glands secrete a large number of a liquid that cleanses the animal's eyes, making the reptile appear to "cry". Soup turtles use this method.
Pupil structure

The pupils of reptiles indicate their lifestyle. Some of them, for example, crocodiles, pythons, geckos, hatteria, snakes, lead a nocturnal or twilight lifestyle, and take sunbathing during the day. They have vertical pupils that dilate in the dark and constrict in light. In geckos, pinpoint holes are visible on the constricted pupils, each of which focuses an independent image onto the retina. Together they create the necessary sharpness, and the animal sees a clear image.

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Remember the movie "The Speckled Band"? There they whistled to call the snake, and then there was a conversation that snakes were deaf and so on. So, I hasten to inform you that snakes are not deaf at all! But they hear a little differently, or rather not at all like we do.
Let's remember the biology course: the organ of hearing consists of the outer ear, the eardrum, to which bones from one to three are connected (depending on the type of animal) they transmit a signal to the cochlea, a three-dimensional spiral-twisted organ in which there are ciliated cells, which actually read sound vibrations due to the fluid filling the cochlea. Somehow like this. What's the problem with snakes? And they do not have an eardrum, nor an external organ of hearing.

But there is a cochlea (blue) and an auditory ossicle (green). And not only that, the auditory ossicle (green) is attached to the large quadrate bone (blue). So why? Ahh... this is where the fun begins! The square bone, together with the jaw, replaces the eardrum. It turns out to be a kind of resonator due to a system of levers, which perceives vibration from the ground and low-frequency waves. The snake can hear you several meters away, even if you walk carefully and quietly. But whistling at a snake like in the movies is really useless. But they perfectly distinguish all the low sounds that we hear. Let's say from my snakes, I see how they flinch from the low bark of my dogs, and how they smell a heavy car driving on the street, and we ourselves are on the fifth floor.

What else is interesting about snakes? And they have thermoreception. These are thermopits in vipers, pythons, boas, and some strange African colubrids.

Here you can clearly see the thermopits on my Python regius on the upper jaw

The most advanced thermal apparatus, let’s say, is that of pit vipers ( Crotalinae). There, inside each hole there are several layers of membranes and a bunch of different thermoreceptors. They are all terribly sensitive! No, they don't see like a thermal imager! Don’t believe the BBC films - the snake doesn’t see any outline of anything there. There is no rhodopsin protein in thermopits; information is read there due to ion channels in the receptor membranes! they show the strength of the object's heat radiation and the direction towards it. All.

In general, whatever you say: but in terms of the number of sense organs and their complexity, the snake will surpass almost any land animal. Next time I’ll tell you how snakes see and why they stick out their tongues.
Well, about the evolution of their poisonous apparatus - that’s a whole different story!

A snake is an animal of the chordate type, class Reptiles, order Squamate, suborder snakes (Serpentes). Like all reptiles, they are cold-blooded animals, so their existence depends on the ambient temperature.

Snake - description, characteristics, structure. What does a snake look like?

The body of the snake has an elongated shape and can reach a length of 10 centimeters to 9 meters, and the weight of the snake ranges from 10 grams to more than 100 kilograms. Males are smaller than females, but have more long tail. The body shape of these reptiles varies: it can be short and thick, long and thin, and sea snakes have a flattened body that resembles a ribbon. That's why internal organs these scaly ones also have an elongated structure.

The internal organs are supported by more than 300 pairs of ribs, movably connected to the skeleton.

The snake's triangular head has jaws with elastic ligaments, which makes it possible to swallow large food.

Many snakes are venomous and use venom as a means of hunting and self-defense. Since snakes are deaf, to navigate in space, in addition to vision, they use the ability to capture vibration waves and thermal radiation.

The main information sensor is the forked tongue of the snake, which allows, with the help of special receptors inside the palate, to “collect information” about environment. Snake eyelids are fused transparent films, scales covering the eyes, therefore snakes don't blink and even sleep with their eyes open.

The skin of snakes is covered with scales, the number and shape of which depends on the type of reptile. Once every six months, the snake sheds its old skin - this process is called molting.

By the way, the color of the snake can be monochromatic in species living in temperate zone, and variegated among representatives of the tropics. The pattern can be longitudinal, transversely circular or spotted.

Types of snakes, names and photographs

Today, scientists know more than 3,460 species of snakes living on the planet, among which the most famous are adders, vipers, sea snakes, snakes (not dangerous to humans), pit snakes, pseudopods with both lungs, as well as rudimentary remains of the pelvic bones and hind limbs.

Let's look at several representatives of the snake suborder:

• King cobra (hamadryad) ( Ophiophagus hannah)
  

The most gigantic poisonous snake on the ground. Some representatives grow up to 5.5 m, although the average size of adults usually does not exceed 3-4 m. King cobra venom is a lethal neurotoxin, causing death in 15 minutes. The scientific name of the king cobra literally means “snake eater”, because it is the only species whose representatives feed on snakes of their own kind. Females have an exceptional maternal instinct, constantly guarding the clutch of eggs and completely going without food for up to 3 months. The king cobra lives in the tropical forests of India, the Philippines and the islands of Indonesia. Life expectancy is more than 30 years.

• Black Mamba ( Dendroaspis polylepis)

The African venomous snake, growing up to 3 m, is one of the fastest snakes, capable of moving at a speed of 11 km/h. The highly toxic snake venom causes death in a matter of minutes, although the black mamba is not aggressive and attacks humans only in self-defense. Representatives of the black mamba species received their name due to the black coloration of the oral cavity. The snake's skin is usually olive, green or brown in color with a metallic sheen. It eats small rodents, birds and bats.

• Fierce snake (desert taipan) ( Oxyuranus microlepidotus)

The most poisonous of land snakes, the poison of which is 180 times stronger than poison cobras This species of snake is common in the deserts and dry plains of Australia. Representatives of the species reach a length of 2.5 m. Skin color changes depending on the season: in extreme heat it is straw-colored, when it gets colder it becomes dark brown.

• Gaboon viper (cassava) ( Bitis gabonica)

The poisonous snake that lives in African savannas is one of the largest and thickest vipers, up to 2 m long and with a body girth of almost 0.5 m. All individuals belonging to this species, have a characteristic, triangular-shaped head with small horns located between the nostrils. The Gaboon viper has a calm character, rarely attacking people. It belongs to the type of viviparous snakes, breeds once every 2-3 years, bringing from 24 to 60 offspring.

• Anaconda ( Eunectes murinus)

The giant (ordinary, green) anaconda belongs to the subfamily of boa constrictors; in former times the snake was called a water boa constrictor. The massive body, 5 to 11 m long, can weigh over 100 kg. The non-poisonous reptile is found in low-flow rivers, lakes and creeks of the tropical part South America, from Venezuela to the island of Trinidad. It feeds on iguanas, caimans, waterfowl and fish.

• Python ( Pythonidae)

A representative of the family of non-venomous snakes is different gigantic size from 1 to 7.5 m in length, and female pythons are much larger and more powerful than males. The range extends throughout the eastern hemisphere: rainforests, swamps and savannas of the African continent, Australia and Asia. The diet of pythons consists of small and medium-sized mammals. Adults swallow leopards, jackals and porcupines whole, and then digest them for a long time. Female pythons lay eggs and incubate the clutch, by contracting muscles, increasing the temperature in the nest by 15 -17 degrees.

• African egg snakes (egg eaters) ( Dasypeltis scabra)

Representatives of the snake family that feed exclusively on bird eggs. They live in savannas and woodlands of the equatorial part of the African continent. Individuals of both sexes grow no more than 1 meter in length. The movable bones of the snake's skull make it possible to open its mouth wide and swallow very large eggs. In this case, the elongated cervical vertebrae pass through the esophagus and, like a can opener, rip open the eggshell, after which the contents flow into the stomach, and the shell is coughed up.

• Radiant snake ( Xenopeltis unicolor)

Non-venomous snakes, the length of which in rare cases reaches 1 m. The reptile received its name for the rainbow tint of its scales, which are dark brown in color. Burrowing snakes live in the loose soils of forests, cultivated fields and gardens in Indonesia, Borneo, the Philippines, Laos, Thailand, Vietnam and China. Small rodents and lizards are used as food items.

• Worm-like blind snake ( Typhlops vermicularis)

Small snakes, up to 38 cm long, resemble earthworms in appearance. Absolutely harmless representatives can be found under stones, melons and watermelons, as well as in thickets of bushes and on dry rocky slopes. They feed on beetles, caterpillars, ants and their larvae. The distribution area extends from the Balkan Peninsula to the Caucasus, Central Asia and Afghanistan. Russian representatives of this species of snake live in Dagestan.

Where do snakes live?

The distribution range of snakes does not include only Antarctica, New Zealand and the islands of Ireland. Many of them live in tropical latitudes. In nature, snakes live in forests, steppes, swamps, hot deserts and even in the ocean. Reptiles lead an active lifestyle both during the day and at night. Species living in temperate latitudes winter time hibernate.

What do snakes eat in nature?

Almost all snakes are predators, with the exception of the Mexican herbivorous snake. Reptiles may only eat a few times a year. Some snakes feed on large and small rodents or amphibians, while others prefer bird eggs. The diet of sea snakes includes fish. There is even a snake that eats snakes: the king cobra can eat members of its own family. All snakes easily move on any surface, bending their body in waves; they can swim and “fly” from tree to tree, contracting their muscles.

Breeding snakes. How do snakes reproduce?

Despite the fact that snakes are solitary individuals by way of life, during the mating period they become quite sociable and “loving.” The mating dance of two snakes of different sexes is sometimes so surprising and interesting that it definitely captivates attention. The male snake is ready to hover around his “chosen one” for hours, seeking her consent to fertilization. Reptiles of the snake order are oviparous, and some snakes are capable of giving birth to live young. The size of a snake's clutch varies from 10 to 120,000 eggs, depending on the type of snake and its habitat.

Having reached sexual maturity at two years of age, snakes begin to mate. The male searches for his “lady” by smell, wraps his body around the female’s neck, rising high above the surface of the earth. By the way, at this time even non-poisonous individuals can be very aggressive due to excitement and excitement.

Mating of snakes occurs in a ball, but immediately after this the pair disperses and never meet again. The snake's parents do not show any interest in newborn babies.

The snake tries to make its clutch in the most secluded place possible: plant roots, crevices in stones, rotten stumps - every quiet corner is important for the future “mother”. The laid eggs develop quite quickly - in just one and a half to two months. Newly born snakes and baby snakes are absolutely independent, poisonous individuals have poison, but these babies can only hunt small insects. Reptiles reach sexual maturity in the second year of life. The average lifespan of a snake reaches 30 years.

What is snake venom? This is saliva produced salivary glands poisonous individuals. Her healing properties known for hundreds of years: with the addition of snake venom, pharmacists make homeopathic preparations, creams, ointments and balms. These remedies help with rheumatic joint diseases and osteochondrosis. However, face poisonous bite This reptile in nature can be not only unpleasant and very painful, but also deadly.

What to do if bitten by a snake? First aid

• If you have been bitten by a snake, and you do not know whether it was poisonous or non-poisonous, in any case you should remove the snake's saliva from the micro-wound! You can suck out and quickly spit out the poison, you can squeeze it out, but all these manipulations will be effective only for the first one to one and a half minutes after the bite.
• The person who has been bitten definitely needs to be urgently taken to a medical facility (hospital).
• At the same time, it is advisable to visually remember what the snake looked like, because its belonging to a certain species is most important for doctors who will prescribe anti-snake serum to the victim.
• If a limb (arm, leg) is bitten, then there is no need to tighten it: this manipulation does not localize the spread of the snake’s venom, but may well lead to toxic asphyxia of the affected tissues.
• Never panic! An increased heart rate due to excitement accelerates blood circulation throughout the body, thereby facilitating the spread of snake venom throughout the body.
• Provide the bitten person with absolute rest, warm fluids, and take him to professional medical professionals as soon as possible.

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