What kind of heart does a crocodile have? The special structure of the crocodile's heart can help it with digestion. The latest data from scientists

Crocodiles are cold-blooded vertebrates that lead a semi-aquatic lifestyle. Water is their favorite medium, being more constant in temperature. It was thanks to her that the ancestors of crocodiles survived the global cooling of the Earth's climate. The body shape of crocodiles is lizard-shaped. The large head is flattened in the dorso-ventral direction, the muzzle is elongated or long, with strong elongated jaws, seated with sharp conical “fangs” up to 5 cm long, which grow throughout the life of the animal, replacing worn out and broken ones. The teeth are strengthened in individual bone cells of the jaws, the base of the tooth is hollow inside; The crocodile's bite is designed in such a way that opposite the largest teeth on the lateral edge of one jaw are the smallest teeth of the other. This design could turn the dental apparatus into a perfect weapon for attack. In narrow-snouted fish-eating gharials, the jaws can be compared to the jaws of tweezers, allowing them to grab small mobile prey in the water with a lateral movement of the head.

The jaw system of Chinese alligators (Alligator sinensis), distributed in Eastern China along the lower reaches of the Yangtze River, is structured differently. These are small reptiles (maximum length 1.5 m), feeding mainly bivalves, water snails, crustaceans, as well as frogs and slow-moving fish species. Such coarse food is ground by the closely set back teeth with a flat crown surface. By rinsing their mouths in water, the fed alligators get rid of fragments of crushed shells and shells.

At the end of the crocodile's snout there are convex nostrils, and the eyes are also raised and located on the upper side of the head. This feature of the skull structure determines the favorite pose aquatic reptile: the body is blissful in the water - only the eyes and nostrils are visible from the outside.

Crocodiles have five fingers on their forelimbs and four on their hind limbs; they are connected by an interdigital membrane. The tail is long, laterally compressed, very powerful and multifunctional: it is “ steering"and "engine" when swimming, support when moving on land, and when hunting - something like a stunning mace. When swimming, the limbs of crocodiles are laid back, the front ones are pressed to the sides, and the powerful flattened tail, bending, describes S-shaped movements. Lying in wait large mammals at the watering hole, huge saltwater crocodile(Crocodylus porosus) attacks suddenly, grabbing a zebra or antelope by the head and breaking its neck, or knocking the victim down with a terrible blow of the tail. During the breeding season, females use their tail to compact what they have brought for the nest. construction material", splash it in the water, spraying the nest with clutches.

The entire surface of the crocodile's body is covered with large, correct form horny scales. The dorsal scutes are thicker and bear convex spiny ridges that turn into serrations on the tail. Each scale develops independently and grows due to the underlying layers. Under the large scutes of skin on the back and tail, a real shell of bone plates, osteoderms, develops. The shields are elastically connected to each other, so they do not restrict the animal’s movements. The shape and surface pattern of the shell is individual for each species. On the head, osteoderms are fused with the bones of the skull. Thus, the animal wears real “armor” that effectively protects vital internal organs and the brain.

The structure of the skull is very unusual. The quadrate and articular bones are penetrated by air-bearing outgrowths of the middle ear cavity. Most of the posterior bones of the skull contain cavities of a highly expanded and complex branching system of eustachian tubes. The bones of the long muzzle and palate also contain significant voids: blind outgrowths of the nasal passage extend into them. Scientists believe that the systems of air cavities and passages that penetrate almost the entire huge skull of the crocodile significantly lighten it, allowing it to hold its head above the surface of the water without significant expenditure of muscle energy (for a silent and imperceptible dive, it is enough for the crocodile to reduce the pressure in the chest cavity and direct part of it into the lungs air from the air cranial passages).

All types of crocodiles have highly organized sense organs. Unlike snakes, they hear perfectly - the range of auditory sensitivity is very large and amounts to 100-4000 Hz. At the same time, crocodiles are deprived of the special “snake” Jacobson’s organ, which allows creepers to distinguish taste and smell with great accuracy. The eyes of crocodiles are adapted for night vision, but also serve well during the day. The retina of the eye contains mainly rod receptors that capture light photons. The pupil, like a cat’s, is capable of narrowing in the light into a narrow vertical slit, and at night the alligator’s eyes have a red-pink glow, which is often taken as constant proof of its bloodthirstiness. It should be said that although the hunting instincts of crocodiles are exacerbated in the dark, ferocious predatory eyes are only a consequence of the anatomical structure of the visual analyzer. In the dark, the vertical pupil dilates, and the bloody color is provided by the presence of a special pigment in animals - rhodopsin - on the retina, illuminated by reflected light. Underwater, the eyes of crocodiles are protected by a transparent nictitating membrane, which closes them when diving.

Everyone knows the expression “shed crocodile tears.” Indeed, crocodiles cry, but not from grief, pain or the desire to treacherously lull someone’s vigilance. In this way, animals are freed from excess organic salts contained in the body. Their muddy tears are unusually salty, but devoid of emotion. Salt glands are located in representatives of the family of true crocodiles, even under the tongue.

The respiratory system of crocodiles also has its own characteristics. The nostrils, like the external auditory openings, can be tightly closed by muscles - they automatically contract as soon as the animal dives. The lungs have a complex structure compared to the baggy lungs of snakes and are capable of holding a large supply of air. As a result, for example, young Nile crocodile only 1 meter long can stay under water for about 40 minutes, without the slightest harm to own health. As for large adult individuals, the duration of their “diving” can reach 1.5 hours. It should be noted that scaly reptiles are not able to absorb oxygen through their rough skin, as thin-skinned amphibians (frogs, newts) do.

The air inhaled through the nostrils passes through paired nasal passages, separated from oral cavity secondary bony palate, which serves as a kind of protection of the skull from the inside. In the case when a crocodile tries to swallow a large and severely mutilated victim, bone fragments and desperate resistance, jerks and blows of the doomed animal are not able to injure the vault of the oral cavity and damage the brain. Just before the choanae (inner nostrils), a muscular curtain descends from above, which presses against a similar outgrowth at the base of the tongue and forms a valve that completely separates the oral cavity from the respiratory tract. Thus, thanks to its anatomical structure a crocodile is able to drown, tear and swallow prey without the risk of choking.

The mechanism of ventilation of the lungs is peculiar and unusual in crocodiles. If for most higher vertebrates the change in volume chest is produced through the movement of the ribs, then the volume of the lungs in crocodiles also changes with the movement of the liver. The latter is moved forward by contraction of the transverse abdominal muscles, causing an increase in pressure in the lungs and exhalation, and then moves backward by the longitudinal diaphragmatic muscles connecting the liver to the pelvis, causing a decrease in pressure in the lungs and, accordingly, inhalation. As researchers K. Hans and B. Clark proved, in crocodiles in water, the main role in ventilation of the lungs is played by the movements of the liver.

The heart of crocodiles consists of four chambers and is much more advanced than the three-chambered heart of other reptiles: oxygenated arterial blood does not mix with venous blood, which has already given oxygen to organs and tissues. The heart of crocodiles differs from the four-chambered heart of mammals in that the latter retain two aortic arches with an anastomosis (bridge) at the crossover. Thus, despite the fact that body temperature, metabolic rate, motor activity and appetite of crocodiles significantly depend on temperature environment, the gas exchange process in their cells is more efficient than in lizards and turtles.

The digestive system of crocodiles is distinguished primarily by the absence of saliva in the oral cavity. In addition, there is another amazing adaptation: in the thick-walled muscular stomach of most adult crocodiles there is a certain amount of stones (the so-called gastrolites), which the animals specifically swallow. In Nile crocodiles, the weight of stones in the stomach reaches 5 kg. The role of this phenomenon is not entirely clear; it is assumed that the stones play the role of ballast and move the crocodile’s center of gravity in front downwards, giving greater stability when swimming and making it easier to dive, or they contribute to the grinding of food when the walls of the stomach contract, as in birds.

Crocodiles do not have a bladder, which is apparently due to life in water. Urine is excreted along with feces through a special organ that removes waste products, located on the abdominal side of the animal (it is called the cloaca). The cloaca has the appearance of a longitudinal slit, while in lizards and turtles it is of a transverse type. In its posterior part, males have an unpaired genital organ. The female lays fertilized eggs, protected on the outside by a dense calcareous shell, and on the inside by primary reserves of food and moisture sufficient for the development of the embryo.

On the sides of the cloaca, as well as under the lower jaw, crocodiles have large paired glands that secrete a brown secretion with a strong musky odor. The secretion of these glands is especially activated during the breeding season, helping sexual partners find each other.

More interesting articles

The life of a crocodile can hardly be called measured. During dry periods these toothy reptiles lie for a long time in the last remaining puddles, slowly using up wisely stored reserves of fat. It's a pitiful sight. But when a holiday comes to their street, crocodiles have few equals in their ability to instantly grab, drown or simply break the victim’s neck. Not being able to chew prey with its powerful but rather primitive jaws, the crocodile tears it into pieces in advance and sends it into the stomach in huge pieces.

The total mass of prey can be up to a fifth of the animal’s own weight.

Of course, these reptiles are far from their relatives, pythons, but it’s hard to imagine a person capable of peeling 15-20 kilograms in one sitting raw meat, and even with bones, it’s quite difficult.

According to American biologists, the crocodile can thank its unique circulatory system for such amazing digestive abilities. Job by scientists at the University of Utah and the Artificial Heart Institute in Salt Lake City has been accepted for publication in the March issue of the journal Physiological and Biochemical Zoology.

In the body of most vertebrates - including crocodiles - blood moves through the so-called two circles of circulation. In the small, or pulmonary, it, passing through the lungs, is enriched with oxygen and gets rid of carbon dioxide; in the large, or systemic, it supplies oxygen to all organs of the body. Actually, neither one nor the other are full circles, since they are closed on each other: from the lungs the blood returns to the beginning great circle, and from organs - small.

In the body of mammals and birds, these circles, however, are clearly separated. In a small circle, blood saturated with carbon dioxide, arriving at the right atrium, is driven into the lungs by the right ventricle. The left ventricle sends oxygen-rich blood coming from the left atrium further throughout the body. In fact, a four-chamber heart is two pumps in one, and this division even allows you to maintain significantly lower pressure in the small circle than in the large circle.

Amphibians and reptiles have a three-chambered heart - its atrium is divided in two, but there is only one ventricle, which sends blood further - both to the lungs and to the organs. It is clear that in this case partial mixing of the blood is possible, which makes the system not very effective. However, cold-blooded lizards and amphibians, who for the most part lead a not very active lifestyle, can afford this.

The crocodile heart is a special case.

It has four chambers, but the circles of circulation are not completely separated. In addition, not only the pulmonary artery departs from the right ventricle, but also an additional, so-called left artery, through which most of the blood is directed to the digestive system, primarily to the stomach. Between the left and right arteries (the right one comes from the left ventricle) there is a foramen of Panizza, which allows venous blood to enter the systemic circulation - and vice versa.

//pharyngula.org/Gazeta.Ru " class="item-image-front">

Structure of the crocodile heart (RV - right ventricle, LV - left ventricle, FP - foramen of Panizza, RA - right aorta, LA - left aorta, PA - pulmonary aorta)
// pharyngula.org/Gazeta.Ru

In humans, this is an anomaly and is called congenital heart disease. The crocodile not only does not feel the defect here, but also has an additional mechanism that allows it to artificially pump oxygen-poor blood into the right artery. Or completely close the left artery, while its circulatory system will work almost the same as in mammals. The crocodile can control this so-called toothed valve at will.

The reasons that prompted nature to create such a remarkable mechanism have long occupied scientists. For a long time it was believed that the heart of a crocodile was a transitional stage on the way to a full-fledged four-chambered heart of warm-blooded mammals.

However, there was an opposite point of view, according to which the crocodile is a descendant of a warm-blooded animal, which, for evolutionary reasons, became more profitable to live the life of a cold-blooded killer. In this case, the Panizza foramen and the serrated valve turn out to be an adaptation mechanism that allowed the transition to a cold-blooded existence. For example, in 2004, Roger Seymour from the Australian University of Adelaide and his colleagues showed that such a heart structure can be very useful for a semi-underwater lifestyle: a decrease in oxygen in the blood can slow down the metabolism, which helps in long dives when a predator is motionless waiting for its kill. sacrifice.

Utah State University professor Colleen Farmer and her colleagues consider, that thanks to this complex system a crocodile can quickly decompose pieces of prey it swallows.

But a crocodile cannot hesitate: if a fish, a monkey, or even human leg, are not digested too quickly, the reptile will die. Either in the mouth of another predator due to its clumsiness, or from hunger and intestinal upset: in a hot climate, bacteria multiply very quickly on a swallowed piece of meat in the belly of an animal.

Farmer believes that the point is not that the blood that has not passed through the lungs is poor in oxygen - to achieve such an effect, you do not need a complex heart structure, but rather slowing down your breathing. In her opinion, the fact is that this blood is rich in carbon dioxide. When a crocodile sends blood rich in CO 2 to the stomach and other digestive organs, special glands use it to produce gastric juice, and the more carbon dioxide they receive, the more active the secretion. It is known that in the intensity of secretion of gastric juice by their glands, crocodiles are ten times higher than the champions in this indicator among mammals. This allows not only to digest food, but also to suppress growth harmful bacteria in the stomach.

To prove their hypothesis, scientists first studied the state of the circulatory system during periods of forced fasting and during the digestion of food by the crocodile. It turned out that in a crocodile that had just eaten, for many hours the valve actually causes the blood to flow predominantly bypassing the lungs.

Next, the scientists surgically deactivated the valve, closing the entrance to the left aorta, in a group of young crocodiles. For the purity of the experiment, the control group was also operated on, but their aorta was not closed. As it turned out, after feeding in crocodiles whose left aorta was blocked, the production of gastric juice was significantly reduced - despite the fact that blood continued to flow to digestive organs in sufficient quantities through the right aorta. At the same time, the ability of crocodiles to decompose bones, which make up a significant part of their diet, also sharply decreased.

In addition to the function of carrying CO 2 to the stomach, Farmer notes, the circulation of blood bypassing the lungs could play another important function, the presence of which many gym-goers would envy.

For a crocodile, a rich meal almost always follows a dash for prey, during which the usually clumsy animal instantly jumps out of the water, grabs the prey that is gaping at the watering hole and drags it under the water. At this time, such an amount of toxic lactic acid is generated in the muscles (it is because of them that after physical activity muscle aches), which can cause the death of the animal. According to scientists from Utah, this acid is also transported through the blood to the stomach, where it is utilized.

As for the foramen of Panizza, its role is not only to direct oxygen-poor blood to other organs, slowing down the crocodile’s metabolism, but also, on the contrary, to supply the digestive system with additional oxygen from the right aorta when needed. The toothed valve helps from time to time send blood rich in carbon dioxide not only to the stomach, but also to other internal organs who may need it.

Researchers from the University of Chicago explained the structural features of the circulatory system of crocodiles. In experiments with American alligators, they were able to show that the ability to let venous blood bypass the lungs to the body tissues is necessary for them to digest food. The scientists' work was published in the journal Physiological and Biochemical Zoology.

Crocodiles, like other reptiles, have preserved right and left aortic arches. However, unlike other reptiles, the crocodile's heart is four-chambered, that is, it is divided into two atria and two ventricles.

The right aortic arch departs from the left ventricle, through which oxygenated blood, after circulating through the lungs, goes to the tissues and organs. The left aortic arch arises from the right ventricle and carries venous blood containing little oxygen. At the exit from the heart, partial mixing of venous and arterial blood from the two aortic arches occurs. The mixing of venous and arterial blood is characteristic of the imperfect circulatory systems of amphibians and reptiles.

However, crocodiles can "severe" the connection between the aortic arches. In this case, venous blood from the left arch does not mix with arterial blood from the right. That is, the main blood circulation proceeds according to a pattern characteristic of mammals.

The left aortic arch leads to the crocodile's stomach. When the junction of the arches is “blocked,” venous blood flowing through the left arch goes straight there. Scientists were able to show that in the glands located in the stomach, reactions occur involving carbon dioxide in the blood, resulting in the formation of bicarbonate and acid, which helps the crocodile digest the bones of its victims. The concentration of acid in the stomach of a crocodile during active digestion is more than ten times higher than the concentration characteristic of mammals.

Crocodiles are known for being able to digest huge amounts of food - up to a quarter of their own weight. If you artificially prevent venous blood from entering the stomach bypassing the lungs, the crocodile's digestion is disrupted and it cannot cope with the digestion of its usual food.

Scientists have put forward several assumptions to explain such a high concentration of acid. Firstly, the acid prevents the growth of bacteria, which is especially important considering that undigested food remains in the crocodile’s stomach for quite a long time. Secondly, bicarbonate is necessary for crocodiles to neutralize large amounts of lactic acid, which is formed in the muscles when attacking the victim. If the blood is not “cleansed” in time, the dose of lactic acid can be fatal. "The Alternate Route" helps the crocodiles do this.

As a third possible reason scientists call the need to quickly secrete a large number of acids. This is especially important for young crocodiles. Digestion proceeds better in warmth, and warm places also attractive to natural enemies, of which there are many for those who have not joined full force young animals As soon as the crocodile enters the heat, it must begin to digest its food, and to do this it needs to quickly secrete a lot of acid, for which it uses the “blocking” of the aortic arches.

Among the most dangerous predators in the world, crocodiles occupy one of the first places ( Latin name– Crocodilia) are the only surviving descendants of dinosaurs, which belong to the order of aquatic vertebrates. Average length adult ranges from 2 to 5.5 meters, and the mass of a crocodile can reach 550-600 kilograms.

External structure of a crocodile

The structural features of crocodiles, both internal and external, help them survive in incredible conditions. It is interesting that, despite the long process of evolution, these reptiles have retained almost all the features of their ancestors, in particular the body of a crocodile , adapted to aquatic environment a habitat:

Few people know that the body of a crocodile can have different colors, although, as a rule, the color of a crocodile is greenish-brown. The upper part of the skin consists of rows of extremely strong and tightly connected horny plates that grow with the individual itself, so that they do not shed. The color of crocodile skin can vary depending on external factors, A more precisely temperatures environment. These animals are cold-blooded, therefore normal temperature The crocodile's body angle varies between 30 and 35 degrees.

Crocodile teeth

Representatives of this species are often confused with alligators, although in reality they have a number of differences, the main of which is the location and structure of the dentition. For example, if the jaws of a crocodile are closed, you can see the 4th tooth from the bottom, whereas in an alligator they are all closed. The total number of teeth in a crocodile is from 64 to 70, depending on the variety, and they have the same conical shape and are hollow. inner surface, where new incisors develop. On average, each crocodile's fang is replaced once every two years, and over the course of a lifetime there can be up to 45-50 such updates. In turn, the crocodile's tongue completely grows to lower jaw, so some generally think that reptiles do not have this organ.

Despite the fact that the crocodile's mouth looks very scary, in fact its teeth are not designed for chewing food, so it swallows its prey in large pieces. The digestive system of a crocodile has a number of specific features, for example, the stomach has very thick walls, and to improve digestion it contains stones (gastroliths). Their additional function is to change the center of gravity to improve swimming performance.

Features of the internal structure of crocodiles

Generally, internal structure the crocodile is similar in structure to other reptiles, but there are some unusual features. For example, the skeleton of a crocodile is very similar to the structure characteristic of dinosaurs: two temporal arches, a diapsid skull, etc. The most vertebrae are found in the tail (up to 37), while in the cervical region and trunk there are only 9 and 17, respectively. For additional protection in the abdominal part there are ribs that are not connected to the spine.

The crocodile's respiratory system is designed in such a way that the animal feels comfortable both on land and under water. The crocodile's respiratory organs are represented by the choanae (nostrils), the nasopharyngeal passage with a secondary bony palate, the palatine curtain, the trachea and the lungs with the diaphragm. The very powerful and complex lungs of a crocodile are capable of holding a large volume of air, while the animal can, if necessary, adjust its center of gravity. To prevent the crocodile's breathing from interfering with its ability to move quickly, there are special muscles in the diaphragm area.

The crocodile’s circulatory system is unique in its own way, which is much more advanced than that of other reptiles. Thus, the crocodile’s heart is four-chambered (2 atria and 2 ventricles), and a special mechanism for mixing blood from arteries and veins makes it possible to regulate the blood supply process. If you need to speed up the digestion process, the structure of the crocodile’s heart allows you to change arterial blood to venous blood, which is more saturated with carbon dioxide and promotes the production of additional gastric juice. It should also be noted that crocodile blood has a high content of antibiotics, and hemoglobin is saturated with oxygen and works independently of red blood cells.

By the way, Bladder these predators do not, but to search for a mate during the breeding season there are special glands on the lower half of the jaw, which emit a musky odor.

Their nervous system is very developed, in particular, the crocodile’s brain (or rather, the cerebral hemispheres) is covered with a cortex, and among the sensory organs, hearing and vision are especially developed. We can say with confidence that the crocodile’s memory is very good, since it manages to remember the paths along which other animals go to the watering hole.

Answer from Lenzel[guru]
Not being able to chew prey with its powerful but rather primitive jaws, the crocodile tears it into pieces in advance and sends it into the stomach in huge pieces.
The total mass of prey can be up to a fifth of the animal’s own weight. Of course, these reptiles are far from their relatives, pythons, but it is quite difficult to imagine a person capable of peeling 15 - 20 kilograms of raw meat, and even with bones, in one sitting.
The crocodile's heart is four-chambered, but the circles of circulation are not completely separated. In addition, not only the pulmonary artery departs from the right ventricle, but also an additional, so-called left artery, through which most of the blood is directed to the digestive system, primarily to the stomach. Between the left and right arteries (the right one comes from the left ventricle) there is a foramen of Panizza, which allows venous blood to enter the beginning of the systemic circulation - and vice versa.
In humans, this is an anomaly and is called congenital heart disease. The crocodile not only does not feel the defect here, but also has an additional mechanism that allows it to artificially pump oxygen-poor blood into the right artery. Or completely close the left artery, while its circulatory system will work almost the same as in mammals. The crocodile can control this so-called toothed valve at will. The reasons that prompted nature to create such a remarkable mechanism have long occupied scientists. For a long time it was believed that the crocodile heart was a transitional stage on the way to the full-fledged four-chamber heart of warm-blooded mammals.
However, there was also an opposite point of view, according to which the crocodile is a descendant of a warm-blooded animal, which, for evolutionary reasons, became more profitable to live the life of a cold-blooded killer. This heart structure can be very useful for a semi-submersible lifestyle: the decrease in oxygen in the blood can slow down the metabolism, which helps in long dives when a predator waits motionless for its prey. Thanks to such a complex system, the crocodile can quickly decompose pieces of prey it swallows.

In her opinion, the fact is that this blood is rich in carbon dioxide. When a crocodile sends CO2-rich blood to the stomach and other digestive organs, special glands use it to produce gastric juice, and the more carbon dioxide they receive, the more active the secretion. It is known that in the intensity of secretion of gastric juice by their glands, crocodiles are ten times higher than the champions in this indicator among mammals. This allows you not only to digest food, but also to suppress the growth of harmful bacteria in the stomach.
But a crocodile cannot hesitate: if a fish, a monkey, or even a human leg is not digested too quickly, the reptile will die. Either in the mouth of another predator due to its clumsiness, or from hunger and intestinal upset: in a hot climate, bacteria multiply very quickly on a swallowed piece of meat in the belly of an animal. It turned out that in a crocodile that had just eaten, for many hours the valve actually causes blood to flow predominantly bypassing the lungs. Source: Also, after feeding in crocodiles whose left aorta was blocked, the production of gastric juice was significantly reduced - despite the fact that the blood continued enter the digestive organs in sufficient quantities through the right aorta. At the same time, the ability of crocodiles to decompose bones, which make up a significant part of their diet, also sharply decreased. For a crocodile, a rich meal almost always follows a dash for prey, during which the usually clumsy animal instantly jumps out of the water, grabs the prey that is gaping at the watering hole and drags it under the water. At this time, such an amount of toxic lactic acid is generated in the muscles (it is because of them that the muscles ache after physical exertion), which can cause the death of the animal. According to scientists from Utah, this acid is also transported through the blood to the stomach, where it is utilized.

Answer from Victor Richert[guru]
like everyone else it's warm

Answer from No[newbie]
cold and slippery

Answer from Marina K[guru]
Big and good! And so soulful! “Crocodile tears” are from emotions!

Answer from Andro Gil[guru]
delicious00000

Answer from Photographer[guru]
Four-chamber

Answer from Natasha[guru]
It has four chambers, but the circles of circulation are not completely separated. In addition, not only the pulmonary artery departs from the right ventricle, but also an additional, so-called left artery, through which most of the blood is directed to the digestive system, primarily to the stomach. Between the left and right arteries (the right one comes from the left ventricle) there is a foramen of Panizza, which allows venous blood to enter the systemic circulation - and vice versa.
In humans, this is an anomaly and is called congenital heart disease. The crocodile not only does not feel the defect here, but also has an additional mechanism that allows it to artificially pump oxygen-poor blood into the right artery. Or completely close the left artery, while its circulatory system will work almost the same as in mammals. The crocodile can control this so-called toothed valve at will.
The reasons that prompted nature to create such a remarkable mechanism have long occupied scientists. For a long time it was believed that the crocodile heart was a transitional stage on the way to the full-fledged four-chamber heart of warm-blooded mammals.
However, there was also an opposite point of view, according to which the crocodile is a descendant of a warm-blooded animal, which, for evolutionary reasons, became more profitable to live the life of a cold-blooded killer. In this case, the Panizza foramen and the serrated valve turn out to be an adaptation mechanism that allowed the transition to a cold-blooded existence. For example, in 2004, Roger Seymour from the Australian University of Adelaide and his colleagues showed that such a heart structure can be very useful for a semi-underwater lifestyle: a decrease in oxygen in the blood can slow down the metabolism, which helps in long dives when a predator is motionless waiting for its kill. sacrifice.