Where reptiles breed. How and where does the reptile embryo develop? Gray monitor lizard and common spiketail

The descendants of extinct dinosaurs are numerous reptiles. The list of reptiles includes about ten thousand species. All of them breathe with lungs, and their skin is covered with horny scales that protect it from drying out. Only on the territory of our country there are 72 species of reptiles.

The list of reptiles includes about ten thousand species.

Class characteristic

The reptile class includes a certain group of cold-blooded animals and has a number of anatomical features. The limbs are located on both sides and widely spaced. During movement, the reptile's body drags along the ground, which does not prevent it from remaining fast and agile at the moment of danger or hunting.

In prehistoric times, this species of fauna lived in the water. In the process of evolution, they switched to a terrestrial existence due to cellular light, dry body covers and internal fertilization. In the process of growth, the animal periodically sheds.

With fish and amphibians, they are united by the body's ability to regulate body temperature according to environmental conditions. In the winter season, they lose activity and hibernate. In the southern latitudes with a hot climate, many of them are nocturnal. The dense horny cover and the absence of glands in the epidermis prevent the loss of moisture.

Distribution area

Reptiles are common on all continents except Antarctica. Their populations are especially numerous in tropical and subtropical regions.

The most viable species live on the territory of the Russian Federation. The list of names of reptiles inhabiting almost all regions of our country is quite extensive. It includes:

1. - Far Eastern, Mediterranean, leathery, Caspian, European marsh, big-headed.
2. lizards- gray and Caspian gecko, motley and eared roundhead.
3. snakes- vipers, snakes, suckers and yellowbellies.

Reptiles include lizards, snakes, turtles

All representatives of this class, living in a temperate climate, are not large in size and prefer small areas for living, since they are incapable of long-distance migrations. They are characterized by high fertility. Females lay dozens of eggs. The density of livestock per hectare can reach one hundred and twenty individuals. Features of nutrition play an important role in the biological indication of nature.

Reproduction features

Reptiles breed on the land surface. Even those who spend most of their lives in the water leave their usual habitat. The mating season is accompanied by increased activity and duels of males. This is especially common in lizards and turtles.

The bulk of reptiles are egg-laying reptiles. In some species, the egg remains in the oviduct until the baby is fully mature. Such animals are ovoviviparous representatives of the fauna.

Reptiles are naturally endowed with a high ability to survive and preserve the species.

Description of individual species

Reptiles are naturally endowed with a high ability to survive and preserve the species. In the wild, there are both herbivorous and predatory reptiles. The list of titles includes:

• turtles;
• crocodiles;
• lizards;
• snake.

Turtles number about three hundred species. Distributed throughout the world. These harmless animals are often kept as pets. They are among the longest living reptiles. Under favorable conditions, they live up to two hundred and fifty years.

A strong shell protects them from predators, and body weight and size depend on belonging to a particular genus and habitat. Sea turtles can weigh up to a ton and have impressive dimensions. Among land species, there are tiny specimens weighing 125 grams and a shell length of 10 centimeters.

The head of the animal is small, which makes it possible in case of danger to quickly remove it under the shell. The reptile has four limbs. The paws of land animals are adapted for digging soil; in marine life, they have turned into flippers.

crocodiles- the most dangerous reptiles. The names of some species correspond to their habitat. The most famous of them:

• marine or combed;
• Cuban;
• Mississippian;
• Philippine;
• Chinese;
• Paraguayan.

Crocodiles are divided into families of gharials, caimans and alligators. They differ from each other in the shape of the jaws and body size.

lizards- quick representatives of the fauna. Most of them are small in size and have a high regenerative capacity. They inhabit different parts of the world, are well adapted to different climatic latitudes.

The main part of the lizards is small and has a high regenerative capacity.

The largest representative of the genus of lizards - komodo dragon. It is named after the island of the same name on which it lives. Outwardly, it resembles a cross between a dragon and a crocodile. They create a deceptive impression with their sluggishness. However, they are excellent runners and swimmers.

Snakes are included in the list of animal reptiles that are devoid of limbs. Due to the elongated shape of the body, the internal organs acquired an identical structure. More than three hundred pairs of ribs located throughout the body help to make flexible movements. The triangular head allows the snake to swallow its prey whole.

In nature, there are a huge number of different snakes. Most of them are poisonous. The poison of some is able to kill within a few minutes. Scientists have long learned to use snake venom as medicines and antidotes.

Snakes lacking venom glands include common snakes and pythons. The largest snake in the world lives on the banks of the Amazon and is called the anaconda. Kills the victim with the help of powerful muscles, wrapping rings around it.

Due to the pressure of water, sea snakes are deprived of a rounded shape and resemble a wriggling ribbon. They are very dangerous to humans, as they produce a highly toxic poison. Once on land, they die within a few hours. Settle in the mouths of rivers flowing into the sea. They rarely swim far from the shore.

Difference from amphibians

Compared to amphibians, reptiles are better adapted to living on land. Their muscles are well differentiated. This explains their ability to make quick and varied movements.

The digestive system is longer. The jaws are equipped with sharp teeth that help to chew even the toughest food. The blood supply is mixed, in which arterial blood predominates. Therefore, they have a higher metabolic rate.

Compared to amphibians, reptiles are better adapted to life on land.

The size of the brain relative to the body is larger than that of amphibians. Features of behavior and sense organs are perfectly adapted to life on the surface of the earth.

Unique reptiles

Among the most interesting and rare reptiles, there are those who have anatomical features unlike other species. The most remarkable representative of the unique fauna is Tuatara. It lives only in one place - New Zealand. With an outward resemblance to a lizard, it does not belong to the genus of these reptiles. The internal organs are similar to snakes.

With an outward resemblance to a lizard, the hatteria does not belong to the genus of these reptiles.

Unlike other animals, it has three eyes, and an additional organ of vision is located in the back of the head. Possessing slow breathing, she is able not to breathe for a minute. The length of the body is half a meter, the weight is about one kilogram.

Reptiles breed on land. Fertilization is internal. Reptiles reproduce in three ways:

- egg production, that is, the female lays eggs;

- egg production when the embryo develops in an egg in the mother's genital tract, it feeds on the nutrients of the egg, from which it hatches shortly after its deposition. (Remember, which are still characteristic of vertebrates egg production and ovoviviparity.);

live birth, in which the embryo develops in the mother's body and receives nutrients from it. For this method of reproduction, the female gives birth to babies. This type of reproduction is inherent only in some sea snakes.

The sex of the offspring that will be born depends on the temperature of incubation of reptile eggs. In crocodiles and turtles incubated at temperatures above +30 C, only females are born, and if the temperature is below this indicator, only males.

In May-June, the female lizard lays in a shallow hole or mink from 6 to 16 large eggs containing a supply of nutrients - the yolk. It is necessary for the embryo to have the opportunity to develop for a long time and be born in the form of a small lizard. Lizard eggs are always covered with a soft, leathery scale-like shell (the shell of turtle and crocodile eggs is hard). Shkaralupna shell prevents damage and drying of the egg. However, in a too dry environment, the eggs can dry out, so sufficient moisture is a necessary condition for the normal development of the embryo.

The development of embryos in eggs continues for two months. At the end of summer, young lizards 4-5 cm long appear from them, which immediately begin an independent life, feeding on the smallest insects. In October, the young are hiding for the winter. The lizard grows throughout its life, its length can be about 25 centimeters. In the second or third year of life, having a length of up to 10 cm, it becomes sexually mature.

The life span of reptiles is the longest among all vertebrates. Lizards live up to 20 years, snakes - up to 60, and crocodiles and turtles can live up to 100. The elephant tortoise lives longer - more than 150 years.

Reptiles are land animals. The transition to a completely terrestrial lifestyle took place due to such features of the adaptation: a dense cover of the body, which prevents moisture loss, and the presence of eggs with protective shells, as a result of which reptiles are able to breed on land.

Terms and concepts: class Reptiles, or Reptiles; horny scales, scutes, rings, autotomy, thoracic, tubular-lumbar, caudal spine, thorax, intercostal muscles, pelvic kidneys, ureters, urethra, larynx, bronchi, Jacobson's organ, live birth, yolk, shell membrane.

Check yourself. 1. What features of the external structure and individual development distinguish reptiles from amphibians? 2. The structure of the integument of reptiles? 3. What is the difference between the skeletons of a lizard and a frog? 4. Name the fundamental differences in the excretion system of lizards and frogs and explain what caused them. 5. What sense organs are most important for the orientation of a lizard? 6. What are oviparous, ovoviviparous and live births?

What do you think? Why do lizards become active in hot sunny weather, and become lethargic during cold weather?

The class Reptiles (reptiles) includes about 9,000 living species, which are divided into four orders: Scaly, Crocodiles, Turtles, Beakheads. The latter is represented by only one relic species - tuatara. The scaly ones include lizards (including chameleons) and snakes.

The quick lizard is often found in central Russia

General characteristics of reptiles

Reptiles are considered the first true land animals, since they are not connected in their development with the aquatic environment. If they live in water (aquatic turtles, crocodiles), then they breathe with lungs and come to land for reproduction.

Reptiles are settled on land much more than amphibians, occupying more diverse ecological niches. However, due to being cold-blooded, they predominate in warm climates. However, they can live in dry places.

Reptiles evolved from stegocephalians (an extinct group of amphibians) at the end of the Carboniferous period of the Paleozoic era. Turtles appeared earlier, and snakes later than all.

The heyday of reptiles fell on the Mesozoic era. During this time, various dinosaurs lived on Earth. Among them were not only terrestrial and aquatic species, but also flying ones. Dinosaurs became extinct at the end of the Cretaceous.

Unlike amphibians, reptiles

improved head mobility due to a larger number of cervical vertebrae and a different principle of their connection with the skull;

the skin is covered with horny scales that protect the body from drying out;

breathing only lung; the chest is formed, which provides a more perfect breathing mechanism;

although the heart remains three-chambered, the venous and arterial circulations are better separated than in amphibians;

pelvic kidneys appear as organs of excretion (and not trunk ones, as in amphibians); such kidneys better retain water in the body;

the cerebellum is larger than that of amphibians; increased volume of the forebrain; the rudiment of the cerebral cortex appears;

internal fertilization; reptiles reproduce on land mainly by laying eggs (some are viviparous or ovoviviparous);

germinal membranes appear (amnion and allantois).

Reptile skin

The skin of reptiles consists of a multi-layered epidermis and a connective tissue dermis. The upper layers of the epidermis become keratinized, forming scales and scutes. The main purpose of the scales is to protect the body from water loss. In total, the skin is thicker than that of amphibians.

Reptile scales are not homologous to fish scales. Horny scales are formed by the epidermis, that is, it is of ectodermal origin. In fish, scales are formed by the dermis, i.e., are of mesodermal origin.

Unlike amphibians, there are no mucous glands in the skin of reptiles, so their skin is dry. There are only a few odorous glands.

In turtles, a bony shell forms on the surface of the body (above and below).

Claws appear on the fingers.

Since keratinized skin inhibits growth, molting is characteristic of reptiles. At the same time, the old covers move away from the body.

The skin of reptiles fuses tightly with the body, without forming lymphatic sacs, as in amphibians.

reptile skeleton

In comparison with amphibians, in reptiles, not four, but five sections are distinguished in the spine, since the trunk section is divided into the thoracic and lumbar.

In lizards, the cervical region consists of eight vertebrae (in different species there are from 7 to 10). The first cervical vertebra (atlas) looks like a ring. The odontoid process of the second cervical vertebra (epistrophy) enters it. As a result, the first vertebra can rotate relatively freely around the process of the second vertebra. This gives more head movement. In addition, the first cervical vertebra is connected to the skull with one mouse, and not two as in amphibians.

All thoracic and lumbar vertebrae have ribs. In lizards, the ribs of the first five vertebrae are attached by cartilage to the sternum. The chest is formed. The ribs of the posterior thoracic and lumbar vertebrae are not connected to the sternum. However, snakes do not have a sternum, and therefore do not form a chest. This structure is associated with the peculiarities of their movement.

The sacral spine in reptiles consists of two vertebrae (and not one as in amphibians). The iliac bones of the pelvic girdle are attached to them.

In turtles, the vertebrae of the body are fused with the dorsal shield of the shell.

The position of the limbs relative to the body is on the sides. In snakes and legless lizards, the limbs are reduced.

Digestive system of reptiles

The digestive system of reptiles is similar to that of amphibians.

In the oral cavity there is a movable muscular tongue, in many species forked at the end. Reptiles are able to throw it far.

Herbivorous species have a caecum. However, most are predators. For example, lizards eat insects.

The salivary glands contain enzymes.

Respiratory system of reptiles

Reptiles breathe only with the lungs, because due to keratinization, the skin cannot take part in breathing.

The lungs are being improved, their walls form numerous partitions. This structure increases the inner surface of the lungs. The trachea is long, at the end it divides into two bronchi. In reptiles, the bronchi in the lungs do not branch.

Snakes have only one lung (the right one, while the left one is reduced).

The mechanism of inhalation and exhalation in reptiles is fundamentally different from that of amphibians. Inhalation occurs when the chest expands due to stretching of the intercostal and abdominal muscles. At the same time, air is sucked into the lungs. When exhaling, the muscles contract and the air is pushed out of the lungs.

The circulatory system of reptiles

The heart of the vast majority of reptiles remains three-chambered (two atria, one ventricle), and arterial and venous blood is still partially mixed. But in comparison with amphibians, in reptiles, the venous and arterial blood flows are better separated, and, consequently, the blood mixes less. There is an incomplete septum in the ventricle of the heart.

Reptiles (like amphibians and fish) remain cold-blooded animals.

In crocodiles, the ventricle of the heart has a complete septum, and thus two ventricles are formed (its heart becomes four-chambered). However, blood can still mix through the aortic arches.

From the ventricle of the heart of reptiles, three vessels independently depart:

From the right (venous) part of the ventricle common trunk of the pulmonary arteries, which further divides into two pulmonary arteries, going to the lungs, where the blood is enriched with oxygen and returned through the pulmonary veins to the left atrium.

Two aortic arches depart from the left (arterial) part of the ventricle. One aortic arch begins to the left (however called right aortic arch, as it bends to the right) and carries almost pure arterial blood. From the right aortic arch originate the carotid arteries going to the head, as well as the vessels supplying blood to the girdle of the forelimbs. Thus, these parts of the body are supplied with almost pure arterial blood.

The second aortic arch departs not so much from the left side of the ventricle as from its middle, where the blood is mixed. This arch is located to the right of the right aortic arch, but is called left aortic arch, as it bends to the left at the exit. Both aortic arches (right and left) on the dorsal side are connected to a single dorsal aorta, the branches of which supply the organs of the body with mixed blood. The venous blood flowing from the organs of the body enters the right atrium.

excretory system of reptiles

In reptiles, in the process of embryonic development, the trunk kidneys are replaced by pelvic ones. The pelvic kidneys have long tubules of nephrons. Their cells are differentiated. In the tubules, water is reabsorbed (up to 95%).

The main excretory product of reptiles is uric acid. It is almost insoluble in water, so the urine is mushy.

The ureters depart from the kidneys, flowing into the bladder, which opens into the cloaca. In crocodiles and snakes, the bladder is underdeveloped.

Nervous system and sense organs of reptiles

The brain of reptiles is being improved. In the forebrain, the cerebral cortex appears from the gray medulla.

In a number of species, the diencephalon forms a parietal organ (third eye), which is able to perceive light.

The cerebellum in reptiles is better developed than in amphibians. This is due to the more diverse motor activity of reptiles.

Conditioned reflexes are developed with difficulty. The basis of behavior is instincts (complexes of unconditioned reflexes).

The eyes are equipped with eyelids. There is a third eyelid - the nictitating membrane. In snakes, the eyelids are transparent and grow together.

A number of snakes at the front end of the head have pits that perceive thermal radiation. They well determine the difference between the temperatures of surrounding objects.

The organ of hearing forms the inner and middle ear.

The sense of smell is well developed. In the oral cavity there is a special organ that distinguishes odors. Therefore, many reptiles stick out a forked tongue at the end, taking air samples.

Reproduction and development of reptiles

All reptiles are characterized by internal fertilization.

Most lay their eggs in the ground. There is a so-called ovoviviparity, when the eggs linger in the genital tract of the female, and when they leave them, the cubs immediately hatch. In sea snakes, a real live birth is observed, while in the embryos a placenta is formed, similar to the placenta of mammals.

Development is direct, a young animal appears, similar in structure to an adult (but with an underdeveloped reproductive system). This is due to the presence of a large supply of nutrients in the yolk of the egg.

In the egg of reptiles, two embryonic shells are formed, which are not found in the eggs of amphibians. it amnion and allantois. The embryo is surrounded by an amnion filled with amniotic fluid. Allantois is formed as an outgrowth of the posterior end of the intestine of the embryo and performs the functions of the bladder and respiratory organ. The outer wall of the allantois is adjacent to the shell of the egg and contains capillaries through which gas exchange takes place.

Caring for offspring in reptiles is rare, it consists mainly in protecting the masonry.

Anatomy, morphology and ecology of reptiles

9. Sex organs and reproduction of reptiles

The sex glands lie in the body cavity on the sides of the spine. testicles - paired oval bodies. Through the appendages, representing the preserved part of the trunk kidney (mesonephros) and containing numerous tubules, the testes are connected to seed tubes , which are the ducts of the mesonephric kidney, i.e., Wolfian channels. The right and left vas deferens open into the corresponding ureters at their confluence with the cloaca.

One of the adaptations for terrestrial existence is internal fertilization. In this regard, the males of all reptiles, except for the tuatara, have special aggregative organs ; in crocodiles and turtles it is unpaired, and in lizards and snakes it is paired outgrowths of the posterior wall of the cloaca, which turn outward during fertilization (Fig. 14).

Rice. 14. Protruding copulatory sacs of a male lizard

Paired ovaries have the appearance of granular oval bodies. Oviducts serve as Mullerian channels. They start shimmering funnels located near the ovaries, and open into the cloaca.

Fertilization occurs in the upper part of the oviduct. The secretions of the secretory glands of the middle part of the oviduct form around eggs(yolk) protein coat , poorly developed in snakes and lizards, and powerful in turtles and crocodiles (Fig. 15).

Rice. fifteen. Scheme of the development of egg membranes in the Central Asian tortoise during the passage of the egg through the oviduct: 1 - egg, 2 - protein shell, 3 - fibrous shell, 4 - shell shell

Outer membranes are formed from the secret secreted by the cells of the walls of the lower part of the oviduct (uterus).

Embryonic development goes the typical way for amniotes. Are formed germinal membranes - serous and amnion - allantois develops. The water necessary for the formation of amniotic fluid and for the normal development of the embryo in lizards and snakes is obtained due to the oxidation of fats. yolk(metabolic water) and absorption of moisture from the external environment, and in turtles and crocodiles with a dense shell - due to metabolic water and the water supply in a powerful protein coat. The minimum soil moisture at which eggs with a fibrous shell can develop normally is about 2.5%, and in the presence of a shell - even up to 1%. Different species lay their eggs in the soil of a certain moisture content that meets the properties of the egg membranes and the needs of the developing embryo.

Most reptiles bury their eggs. into the ground in well-heated places; some species lay their eggs in heaps of plant debris or under rotting stumps, using the heat generated during decay. Some crocodiles dig holes and cover their eggs with plant debris; females stay at the nest and guard the clutch. Guard masonry and some large lizards (lizards, etc.). Python females wrap their bodies around the egg laying, not only protecting it, but also heating it: in such a “nest” the temperature is 6-12 ° C higher than the environment. In crocodiles, the female guarding the nest digs out the masonry when the cubs hatch, making it easier for them to reach the surface; in some species, the females guard the young even during the first period of their independent life. Females of some skinks and spindles also do not leave the clutch, protecting them from enemies.

In a relatively small number of modern squamous species (order Squamata), there is ovoviviparity or less often live birth. The common viper - Vipera berus, viviparous lizard - Lacerta vivipara, spindle - Anguis fragilis fertilized eggs delayed in the genital tract of the female, passing through all stages of development there; the embryos hatch immediately after oviposition.

Oviparous also characteristic of sand boas - Eryx, sea snakes, some snakes and lizards. Oviparous production developed from cases of temporary retention of eggs in the oviducts noted for a number of species of lizards and snakes. So, in ordinary snakes - Natrix natrix, the duration of egg development in the external environment can vary between 30-60 days, depending on how long they were in the mother's body. Some species switch to ovoviviparity only under certain conditions. Tibetan roundhead - Phrynocephalus theobaldi at an altitude of 2-3 thousand meters above sea level lays eggs, and above (4-5 thousand meters) - ovoviviparous. The viviparous lizard - Lacerta vivipara in the south of its range (France) lays eggs, and its northern populations are ovoviviparous.

True live birth known in some skinks (Chaleides, Lygosoma, Taliqua). They lack the outer shell of the eggs, the embryonic shells of the developing embryo adjoin to the walls of the uterine oviduct; by osmosis and diffusion, oxygen and nutrients from the mother's bloodstream enter the circulatory system of the embryo. Some snakes (already - Thamnophis sirtalis, etc.) and lizards form a real placenta: outgrowths of the serous membrane and allantois of the embryo are introduced into the mucous membrane of the uterine part of the mother's oviduct. Due to the close proximity of the blood vessels of the female and the embryo, the supply of oxygen and nutrients to the embryo is facilitated. Development in the mother's body provides the best temperature conditions for embryogenesis, and therefore both forms of viviparity predominate. in the north and in the mountains. Viviparity is sometimes associated with an arboreal and aquatic lifestyle: some chameleons and water snakes have it.

Puberty occurs at different times: in crocodiles and many turtles at the age of six, ten, in snakes more often in the third or fifth year of life, in large lizards in the second or third year, and in small ones - in the ninth or tenth month of life.

Fertility reptiles are much lower than the fertility of amphibians. Its decrease is associated with a reduction in embryonic mortality due to the sheltered placement of clutches, and in a few species, their protection and ovoviviparity. An important role is played by direct development, without metamorphosis and change of habitats; the latter is always accompanied by high mortality. Reduces the death and high mobility of hatchlings and their secretive way of life. Clutch size rarely exceeds one hundred eggs (some crocodiles, large turtles and snakes); more often it is limited to 20-30 eggs. Small species of lizards lay only 1-2 eggs, but several times a season.

In some lizards (Caucasian rock lizards - Lacerta armenica, Lacerta dahli, Lacerta rostombecovi, North American teiids - Cnemidophorus, possibly in some of the agamas and in the gecko - Hemidaetylus turcicus), it has been established or assumed parthenogenetic reproduction, i.e., the development of laid unfertilized eggs (I. S. Darevsky). Populations of these species are only from females. Parthenogenesis in lizards is usually observed in peripheral populations, i.e., on the borders of the range. In such a situation, the existence of a same-sex population of only females becomes advantage, since it allows the limited food reserves to be spent most efficiently, only on the individuals producing cubs. This can be supported by natural selection, but it represents a dead end of evolution, since it excludes panmixia and the recombination of genes associated with it, which sharply limits variability.

Finally, a surprising case is found in snakes hermaphroditism(bisexuality, or intersexuality). The snake, the island botrops Bothrops insularis, lives only on about. Queimada Grande with an area of ​​​​only 3 km (60 km from the city of Santos in southern Brazil), most females, along with the ovaries, have male copulatory organs and fully developed testes. Apparently, in a small island population, such intersexuality allows you to increase the rate of reproduction without increasing the number of inhabitants. It has been noted that over the past 50 years, the proportion of males in the population has decreased.

Ecological Center "Ecosystem" purchase color identification table " Amphibians and reptiles of central Russia"and a computer determinant of reptiles (reptiles) of Russia and the USSR, as well as other methodological materials on animals and plants of Russia(see below).

On our website you can also find information on anatomy, morphology and ecology of reptiles:

Caring for offspring in reptiles (reptiles).

1. Features of reproduction of reptiles. Reptiles breed by laying relatively large, in comparison with amphibians, eggs in dense shells - either in a leathery elastic film or in a hard shell, like in birds. One female usually lays several clutches during the season. Some reptiles build special nests for laying eggs. These can be holes dug in a suitable place, in which the female lays eggs, and then sprinkles them with sand or earth; or the simplest hiding places like piled up leaves or nesting chambers in a burrow. However, most reptiles do not arrange any special nests, but leave eggs in loose soil, cracks and hollows of trees, in burrows under objects lying on the ground. But at the same time, the female chooses a place where the clutch is most protected from predators, adverse environmental conditions, and where temperature and humidity are maintained suitable for the development of embryos. The incubation of eggs lasts quite a long time, the cubs hatch completely independent and outwardly very similar to their parents. Many lizards and snakes bring live young immediately.

2. Parental behavior of reptiles. Only a few reptiles guard their clutches, and almost none of them care about the fate of the cubs that are born. The only exceptions are crocodiles, which carry hatching crocodiles from the nest into the water. Moreover, many reptile mothers, on occasion, can eat their own offspring.

Sea turtles make long-distance migrations in order to breed on certain parts of the sea coasts. They gather in these places from different regions, often located many hundreds of kilometers away. For example, a green turtle, heading from the coast of Brazil to Ascension Island in the Atlantic Ocean, overcomes a distance of 2600 km, fighting currents and maintaining an accurate course. Arriving at the breeding grounds, the turtles mate near the shore. Mating is very fast. The male claws very strongly and pulls the female's shell. On land, the female moves with great difficulty, clumsily pushing her body forward and leaving behind a wide track, similar to the track of a caterpillar tractor. She moves slowly and is completely subordinated to the desire for one single goal - to find a suitable place for masonry. Having got out of the surf line, the female carefully sniffs the sand, then rakes it and makes a shallow hole, in which she then digs a jug-shaped nest with the help of only her hind limbs. The shape of the nest is the same in all species of turtles. During the breeding season, females lay eggs two to five times; in laying from 30 to 200 eggs. Turtles that mate in the sea often start mating again immediately after the female has laid her eggs. Obviously, the sperm must be preserved during the entire period of time between clutches.

There is no parental behavior in turtles; after laying eggs, they go back to the sea, and, having hatched, the cubs make their way from the shore to the water and further without parents.

Crocodiles lay their eggs in peculiar nests made of sand, clay and stones. They carefully guard the "nest", and after hatching the cubs very carefully carry them to a safer place.