Reproduction of frogs, where they lay eggs. Development of a frog from egg to individual in an unnatural habitat under different external conditions. Transformation from egg to frog.

Frogs can reproduce when they reach four years of age. Waking up after hibernation, sexually mature amphibians immediately rush to spawning reservoirs, where they search for a partner of suitable size. The male has to perform various types of tricks in front of the female in order to attract her attention, such as songs and dances, and showing off with might and main. After the female chooses a suitor that she likes, they begin to look for a place to lay eggs and fertilize them.

Mating games

Voice

Most male toads and frogs attract females of their species by voice, namely by croaking, which different types different: in one species it is similar to the “trill” of a cricket, and in another it is similar to the usual “kva-kva”. You can easily find the voices of males on the Internet. The loud voice in the pond belongs to the males, while the females have a very quiet voice or no voice at all.

Courtship

• Appearance and color.

The males of many species of frogs, for example, tropical dart frogs, change their color during mating time and become black. Males, unlike females, have larger eyes, better developed sensory organs and an enlarged brain, respectively, and the front paws are decorated with so-called nuptial calluses, which are necessary for mating so that the chosen one cannot escape.

• Dance

The attention of females can be attracted by various movements . Colostethus trinitatis simply jump rhythmically on a branch, and Colostethus palmatus gets into exquisite poses when they see a female on the horizon, and other species living near waterfalls manage to wave their paws at the females.

Colostethus collaris males perform a courtship dance. The male crawls up to the female and croaks louder and faster, then crawls away, sways and jumps, while freezing on his hind legs in a vertical position. If the female is not impressed by the performance, she raises her head, showing her bright yellow throat, this discourages the male. If the female liked the male’s dance, then she watches the beautiful dance, crawling into different places to better see the male's game.

Sometimes a large audience can gather: once scientists, observing Colostethus collaris, counted eighteen females that stared at one male and synchronously moved to another position. After dancing, the male slowly leaves, often turning around to make sure that the lady of his heart is following him.

On the contrary, golden poison dart frogs have females fight for males. Having found a male who is croaking, the female slaps her hind legs on his body and places her front paws on him, and may also rub her head against the male's chin. The male with less ardor responds in kind, but not always. Many cases have been recorded when fights arose in this species of amphibian both between females and males for the partner they liked.

Fertilization or how frogs reproduce

Fertilization occurring externally

This type of fertilization occurs most often in frogs. The smaller male firmly clasps the female with his forepaws and fertilizes the eggs that the female lays. The male embraces the female in an amplexus position, which there are three options.

1. Behind the front legs of the female, the male makes a girth (sharp-faced frogs)
2. The male grasps the female in front of the hind limbs (scaphiopus, spadefoot spadefoot)
3. The female is grabbed by the neck (poison dart frog).

Fertilization occurring internally

A few poison dart frogs (for example, Dendrobates granuliferus, Dendrobates auratus) are fertilized in a different way: the female and male turn their heads in opposite directions and connect their cloaca. In the same position, fertilization occurs in amphibians of the species Nectophrynoides, which first bear eggs and then tadpoles in utero until the process of metamorphosis is completed and give birth to fully formed frogs.

Male tailed frogs of the genus Ascaphus truei have a specific organ for reproduction.

During the breeding season, males quite often develop specific nuptial rough calluses on their front paws. With the help of these calluses, the male holds on to the slippery body of the female. Interesting fact: for example, in the common toad ( Bufo bufo), the male climbs onto the female far from the reservoir and rides her for several hundred meters. And some males may ride the female after the mating process is complete, waiting for the female to form a nest and will lay eggs in it.

If the mating process takes place in water, the male can hold the eggs laid by the female, tucking his hind legs in order to have time to fertilize the eggs (species - Bufo boreas). Quite often males can get confused and mount males who clearly don’t like it. The “victim” reproduces a specific sound and vibration of the body, namely the back, and forces him to get off himself. Females also behave in the same way at the end of the fertilization process, although sometimes the male can release the female himself when he feels that her abdomen has become soft and empty. Quite often, females actively shake off males who are too lazy to get off, turning over on their side and stretching out their hind limbs.

Coitus - amplexus

Types of amplexus

Frogs lay eggs, like fish, since caviar (eggs) and embryos lack adaptations for development on land (anamnia). Various species of amphibians lay eggs in Amazing places:

During the entire period of gestation of the tadpoles, which lasts two months, the frog does not eat anything, but remains active. During this period, she uses only internal reserves of glycogen and fat, which are stored in her liver. After the gestation process, the frog's liver decreases three times in size and there is no belly fat left under the skin.

After laying eggs, most females leave their clutch, as well as spawning waters, and go to their usual habitats.

The eggs are usually surrounded by a large female layer of gelatinous substance. The egg shell plays a big role, since the egg is protected from drying out, from damage, and most importantly, it protects it from being eaten by predators.

After laying, after some time, the shell of the eggs swells and forms into a transparent gelatinous layer, inside of which the egg is visible. The upper half of the egg is dark, and the lower half, on the contrary, is light. The dark part heats up more, as it uses the sun's rays more efficiently. In many species of amphibians, lumps of eggs float to the surface of a reservoir, where the water is much warmer.

Low water temperature delays the development of the embryo. If warm weather, the egg divides many times and forms into a multicellular embryo. Two weeks later, a tadpole emerges from the egg - a frog larva.

Tadpole and its development

After hatching tadpole falls into water. After only 5 days, having used up the supply nutrients eggs, he will be able to swim and feed on his own. It develops a mouth with horny jaws. The tadpole feeds on protozoa algae and other aquatic microorganisms.

By this time, the tadpoles’ body, head, and tail are already visible.

The tadpole has a large head, there are no limbs, the caudal end of the body plays the role of a fin, a lateral line is also observed, and there is a sucker near the mouth (the genus of the tadpole can be identified by the sucker). Two days later, the gap along the edges of the mouth is overgrown with some semblance of a bird's beak, which serves as a nipper when the tadpole feeds. Tadpoles have gills with branchial openings. At the beginning of development, they are external, but during the development process they are modified and attached to the gill arches, which are located in the pharynx area, while functioning as ordinary internal gills. The tadpole has a two-chambered heart and one circulation.

In terms of anatomy, the tadpole at the beginning of development is close to fish, and when it matures, it already resembles the species of reptiles.

After two to three months, the tadpoles grow back and then front legs, and the tail first shortens and then falls off. At the same time, the lungs also develop. Having formed for breathing on land, the tadpole begins its rise to the surface of the reservoir to swallow air. Change and growth depend largely on hot weather.

Tadpoles at first feed mainly on food of plant origin, but then gradually switch to food of animal origin. A fully formed frog can go ashore if it is a terrestrial species, or continue to live in the water if it is an aquatic species. The frogs that have made it to land are fingerlings. Amphibians that lay eggs on land sometimes proceed to development without the process of metamorphosis, that is, through direct development. The development process takes about two to three months, from the beginning of laying eggs to the end of the development of the tadpole into a full-fledged frog.

Amphibian dart frogs show interesting behavior. After the tadpoles hatch from the eggs, the female carries them on her back, one by one, to the tops of trees in flower buds, in which water accumulates after rain. This kind of pool is a good children's room where children continue to grow. Their food is unfertilized eggs.

The ability to reproduce in cubs is achieved approximately in the third year of life.

After the breeding process green frogs stay in the water or stay on the shore near a reservoir, while brown ones move to land from the reservoir. The behavior of amphibians is largely determined by humidity. In hot, dry weather, brown frogs are mostly invisible, as they hide from the sun's rays. But after sunset it is time for them to hunt. Since the green type of frog lives in or near water, they hunt during daylight hours.

With the onset of the cold season, brown frogs move to the pond. When the water temperature becomes higher than the air temperature, brown and green frogs sink to the bottom of the reservoir for the entire period of winter cold.

Frogs are the most well-known tailless amphibians. They occupy an intermediate place between terrestrial and aquatic vertebrates.
The life of amphibians deserves attention, primarily because they occupy a special place in the history of the development of terrestrial vertebrates, being the first and most primitive inhabitants of land. Assess the importance of amphibians in nature and economic activity human beings is possible with further study of amphibians, the biology of which has been developed only extremely superficially. The use of this animal to study biological issues gave recognition to the frog's enormous merits in medicine.

Firstly, the lake frog is a destroyer of harmful animals. This representative of the amphibian order as an adult feeds exclusively on animal food and, living in a wide variety of places, brings benefits by eating harmful insects. The importance of amphibians also increases because they, in greater numbers than birds, eat insects with an unpleasant odor and taste, as well as insects with patronizing coloring. Also worthy of special attention is the fact that land species Amphibians are hunted at night, when the vast majority of insectivorous birds are asleep.

Secondly, amphibian frogs are a food source for some fur-bearing animals. Frogs make up more than one third of all mink food, a valuable fur-bearing animal confined to water bodies. The otter also readily eats amphibians. Amphibians are relatively often found in the stomachs of badgers and black polecats. Finally, many commercial fish in lakes and rivers in winter period They eat frogs in large quantities, which turn out to be quite accessible mass food.

Of course, there are also negative aspects when frogs destroy young fish in large quantities. Attracted by clusters of fry, numerous lake frogs turn out to be their main enemies here.

In some cases, frog tadpoles can compete with fish for food. Behind Lately there were indications of negative meaning amphibians in nature as guardians of dangerous infectious diseases, such as tularemia.

Third, amphibians are valued as laboratory animals. The ease of dissection of the frog, its suitable size and vitality have made it a favorite experimental subject for a long time. Most devices in experimental medicine and biology are designed for this animal. The technique of physiological experiment is constantly being developed on the frog. A huge number of experiments and observations have been and are being carried out on these “martyrs of science.” Laboratories of large educational and scientific institutions consume tens of thousands of frogs per year. This expense can be so great that it becomes necessary to take measures so as not to destroy all the animals. Thus, in England, frogs are now protected by law, and catching them is prohibited.

Thus, the question arises about the relevance of raising frogs in an artificial environment.

All this made it possible to determine the topic of scientific work.

Purpose of the study: find out under what different, artificially created conditions, the frog larva will go through all stages of metamorphosis faster.

Research objectives:
1. Explore scientific literature in biology;
2. Identify the reasons for positive and negative influences environment for development;
3. Conduct research work.

Object of study: caviar of a common frog.

Hypothesis: Various external conditions affect the development of a frog from eggs to individuals. unnatural environment a habitat. If you create everything the necessary conditions, then you can achieve the maximum percentage of tadpole survival.

Reliability of results is ensured by the personal participation of the author in the research process.

Lake frog

Description

Lake frog- a species of tailless amphibians of the family of true frogs. The lake frog is the most close-up view amphibian fauna of Russia: its body length can reach up to 150 mm.

Tailless - largest squad amphibians, numbering about 6,000 modern and 84 fossil species. Representatives of the order are often called frogs, but the use of this term is complicated by the fact that only representatives of the family of true frogs are called frogs in the narrow sense. The larvae of tailless amphibians are tadpoles.

Class - Amphibians, order - Tailless, family - Frogs, Genus - Frogs.

Size 6-10 cm. Average weight 22.7 gr. The muzzle is blunt, the body is squat. The eyes are brown with black horizontal pupils. The inner eyelid is transparent, protecting the eyes in water. A dark brown triangle is clearly visible near the eardrum. The skin of a frog is slimy and smooth to the touch; its epidermis does not keratinize. There is a marble-like pattern on the dark belly. The internal calcaneal tubercle is low.

In males, external resonators of a dark gray color are located in the corners of the mouth. On the first (inner) finger of the forelimbs of males there is a skin thickening - a callus, which grows during mating.

The class of amphibians requires oxygen to live. The frog can obtain it on land and partially underwater through the skin. The respiratory organs of amphibians, which include frogs, are lungs, skin and gills. Unlike tadpoles, which lead an aquatic lifestyle, adult frogs do not have gills. Oxygen dissolved in water enters the blood of these creatures through the skin. This method of breathing can provide the body with the necessary gas only if the frog is in a state of hibernation.

A frog can stay under water for a long time, because... she has a very big lungs. Before diving, the animal takes in full lungs of air. Under water, oxygen is absorbed very slowly through the blood arteries, which helps the frog stay under water for a long time. As soon as the air reserves run out, the animal quickly surfaces and holds its head above the surface of the water for some time in order to regain full lungs of air.

Frogs never drink. Liquid enters their body through the skin.

The adult breeds in water, but prefers to spend most of its life on land, choosing very damp and shaded places to live.

On land, frogs hunt by catching insects, which are their main diet. In vegetable gardens located in lowlands near water bodies, fruit trees, shrubs and vegetable crops are almost never affected by pests, since frogs are cleaning animals. Just a few frogs can destroy hordes of insect pests.

Breeding season is April - early May. Reproduction occurs in puddles, ponds, lakes, canals, and in any shallow body of water. Spawning begins 3-5 days after waking up. Males appear on reservoirs earlier; they sing mating songs, inviting females. Having spawned, the grass frog does not linger in the reservoir and disperses to its summer habitats. The eggs are light yellow in color, surrounded by a thick layer of gelatinous substance. This shell has great importance for the embryo, since in this way the egg is protected from drying out, from mechanical damage, and most importantly, it protects them from being eaten by other animals. They are connected into clusters of quite significant size, and sometimes into cords; a lot of them are put aside. One female lays 670-1400 small eggs.

Use in science

“And how many frogs are countless,
They can be counted and counted endlessly, -
They gave frog legs to science,
They gave their hearts for the benefit of science.”
L. Gainulina

Lake frogs are often captured as laboratory animals for scientific, medical and educational institutions.
For example, students of the Orenburg State Pedagogical University use up to 3,000 individuals of the lake frog to conduct workshops on physiology and zoology during one year of study.

Quite a lot of biologically active substances have been discovered in frogs, but they have been studied much less than those in toads.

It has long been known that if you put a frog in milk, it will not turn sour for a very long time. Modern research The antimicrobial properties of the mucus covering the skin of the frog have been confirmed. This prevents the proliferation of fermented milk bacillus.

A number of substances with biological activity have been extracted from the skin of different species of frogs.

Some of these substances effectively kill bacteria, others have vasodilating properties. A substance with a choleretic effect and also stimulating the secretion of gastric juice was isolated from the skin of the white Australian tree frog. From this substance it is possible to make a drug for the treatment of certain mental illnesses.

Dermorphins were found in the skin of one species of frog, which have an analgesic effect 11 times greater than morphine.

Frog neurotoxins are some of the most powerful. Batrachotoxin, isolated from the Colombian frog, local residents called "cocoa", is the most potent of the non-protein poisons, stronger than potassium cyanide. Its action is similar to that of curare.

Substances isolated from some South American tree frogs, act on the transmission of nerve impulses in skeletal muscles. Some block smooth muscle receptors, while others cause skeletal and respiratory muscle spasms.

Currently, these substances are not used in medicine; the possibility of including them in clinical practice is being explored.

The antimicrobial and wound-healing properties of frog caviar have been scientifically confirmed - the substance ranidone, which has high bactericidal activity, has been isolated from the shell of the caviar.

No matter how we feel about frogs, they are one of the most common, frequently used laboratory animals, along with rats and mice. For example, the clawed frog was the first animal to be cloned, and not Dolly the sheep, as we used to think. In the 1960s, English embryologist Gurdon cloned tadpoles and adult frogs.

For his services in the field of medicine, monuments were erected to the frog in Paris, Tokyo and Boston, as a tribute to and recognition of the truly invaluable services of these animals in the development of science. This is how scientists thanked their unwitting assistants in many important scientific research and discoveries. The experiments of the 18th century Italian physicists Luigi Galvani and Alessandro Volta, carried out on frogs, led to the discovery of galvanic current. Physiologist Ivan Sechenov conducted a huge number of experiments on frogs. In particular, he used them in studying the nervous activity of animals. And the frog’s heart turned out to be an interesting object for studying cardiac activity. The French physiologist Claude Bernard, to whom frogs also helped make a number of discoveries, expressed the idea of ​​erecting a monument to them. And at the end of the 19th century, the first monument to frogs was opened at the Sorbonne (University of Paris). And the second was erected by medical students in Tokyo in the 60s of the 20th century, when the number of frogs they used for science reached 100 thousand.

In addition to scientific value, these amphibians have practical value. Thus, in many countries, the meat of certain types of frogs is considered a delicacy. There are even special farms where frogs are bred for meat.

Practical work

So, let's get started:

05/07/15 The eggs were taken from a pond surrounded by bushes and aquatic plants.

The shell of each egg is swollen, similar to a gelatinous transparent layer, inside of which the egg is visible. Its upper half is dark and the lower half is light.

In nature, the rate of egg development depends on the water temperature. The higher the temperature, the faster the development. In deep, shaded reservoirs, eggs develop approximately four times slower than in well-warmed reservoirs. Caviar easily withstands low temperatures.

We create optimal conditions for the development of eggs: room temperature, warm.

After 8-10 days, tadpoles hatch from the eggs, more like fish fry. Passive, do not feed. Apparently there is enough nutritional supply of eggs. There are gill openings and gills.

05/23/15 Metamorphosis is noticeable. The tadpoles began to feed independently, move actively, and stay closely together. They scurry in different directions, but do not swim far, and the entire flock moves almost simultaneously. The average size of tadpoles is approximately 7-8 mm.

By this time, the head, body, and tail are already visible. The head is large, there are no limbs, the caudal section of the body is a fin, a lateral line is also present, and oral cavity looks like a suction cup. The gills are initially external, attached to the gill arches located in the pharynx area, and function as real internal gills.

The suction cup is located at the bottom near the mouth (you can use it to determine the type of tadpole); after a few days, the gap in the mouth along the edges becomes overgrown with some semblance of a beak, which works like nippers when the tadpole feeds. The tadpole has one circulation and a two-chambered heart.

In terms of body structure, amphibian larvae are close to fish, and adults are similar to reptiles.

In nature, tadpoles sometimes form huge aggregations - up to 10,000 in one cubic meter of water. It is not for nothing that among the ancient Egyptians the image of a tadpole meant the number 100,000, i.e. “very many.” But not all of them survive. The frog larva serves as food for fish, birds, swimming beetles and other inhabitants of the reservoir.

We place the tadpoles in different containers:

We place an absolutely transparent plastic container (10 l) in a well-lit area, in a warm place Not in the zone direct hit sun rays (balcony) – 25 pcs.

We place an absolutely transparent glass container (3 l) in a well-lit area, in a warm place in an area of ​​direct sunlight (balcony) - 10 pcs.

Place a dark, opaque container (5 liters) in a warm place, slightly shaded, but with sufficient light. No direct sunlight (room) – 30 pcs.

We place an opaque container (2 l) in a poorly lit, cool place (garage) - 10 pcs.

All containers are filled with water taken from the place where the eggs were collected, i.e. closest to the breeding conditions, as well as algae and grass. Microorganisms are observed in water.

Within two days no differences in behavior are observed. All tadpoles are mobile, hide in mud and grass, and actively respond to sound and movement. They feed on plant foods during the day, as if biting them off, and also scrape off plaque from surfaces. They periodically rise to the surface of the water and swallow air. The growth rate is not striking; as is known, it averages 0.6 mm per day.

05/25/15 In a glass container located in an area of ​​direct sunlight, all the tadpoles died by evening. At the same time, without preserving the contours of the body, it almost completely decomposed and disappeared. Externally, the surface of the water in the container looked like it was bubbling, as if it had turned sour.

Conclusion: tadpoles, despite the statement that complete metamorphosis occurs faster with more high temperatures(21-26 C), and on average it lasts 50-90 days, they do not tolerate direct sunlight.

Cover the completely transparent plastic container with paper, protecting it from the sun.

05/28/15 IN plastic container, even though it is not in direct sunlight, the tadpoles are passive and remain practically motionless. The water is very hot. Several died. We remove it to a more shaded place.

In the remaining containers, the tadpoles are still active. They are in almost constant motion and feeding.

The growth of tadpoles is already more noticeable. The average is approximately 10 mm.

We add fresh water and algae from the reservoir, but not from the laying site, to all containers with tadpoles.

06/01/15 Transparent, highly permeable daylight in a container placed in the shade, the tadpoles increased in growth. There was a sharp difference between larger and smaller tadpoles. Large ones are approximately 13-15 mm. They eat all the time, stick to the walls, grab air. The eyes and marble body pattern are clearly visible.

In an opaque container that practically does not allow daylight to pass through, but is located in a warm place, the growth of tadpoles is practically unnoticeable, as is the case in a container located in a cool, dark place. Several died despite the presence of food and the absence of direct sunlight.

Conclusion: There is high mortality during development, even in the absence of external predators feeding on the tadpoles.

For 3 weeks with constant feeding and changing water in containers, because Products of food processing by tadpoles accumulated at the bottom, the death of some specimens and the growth of stronger ones were observed. The average size is already approximately 20-25 mm.

The highest mortality rate was in a transparent container located in a warm place. Possibly from a constant change in water temperature: from very warm, heated by the sun to daytime, until it cools down very much at night.

06/27/15 The tadpole in the garage has undergone visible metamorphosis: hind legs have appeared.

07/03/15 Over a short period of time, the tadpole takes the form of a small frog. The front legs have grown, the tail has shortened. At the same time, the young frog appears to be smaller in size, what was the tadpole from which it was just formed.

Thus, as in nature, from the moment the eggs are laid to the end of the transformation of the tadpole into a frog, about 2-3 months pass.

Metamorphosis of a frog: 1 - eggs (spawn), 2 - tadpole with external gills, 3 - without gills, 4 - with hind legs, 5 - with all legs and a tail, 6 - frog.

The luckiest of the tadpoles survive to the stage of metamorphosis and turn into a young frog. Fingerlings are very voracious. The volume of their stomach when full exceeds one fifth of their total weight. There is one interesting detail: if there is not enough animal food in the reservoir, the herbivorous tadpole spends the winter in larval stage, postponing the transformation from vegetarian to carnivore until spring. They become fully carnivorous once their hind legs develop, feeding on small aquatic animals or even other tadpoles when food is scarce.

07/05/15 As is known in nature, tadpoles feed on algae, plant matter, and larvae of small microorganisms. In captivity, possibly due to shortage plant food(despite its presence in the container), the tadpoles ate the newly formed frog, and not vice versa.

Conclusion

Thus, we conclude that tadpoles are very fragile organisms. Our hypothesis was confirmed.

1. Mortality of eggs and tadpoles reaches 80.4 - 96.8%.

Of enough large quantity hatched tadpoles, 11 survived. Moreover, 5 out of 30 are in a dark, opaque container (5 l), located in a slightly shaded room, without direct sunlight.

3 out of 10 - in a light, opaque container (2 l), located in a poorly lit, cool place, in the garage. At the same time, a frog formed ahead of everyone else.

Frogs reproduce by spawning eggs. Almost all frogs lay eggs in the spring. But all types of frogs do this in their own way, some build nests, others do it right in the pond, and some carry their offspring on their backs. The most interesting methods of reproduction are, of course, frogs living in tropical places South America. Our frogs are less inventive and spawn on coastal vegetation in shallow water, where the water warms up well. If you keep frogs in a pond, the breeding process can be easily monitored. You may not see the eggs, but you can immediately see when the tadpoles appear. The development of frogs can be traced on tadpoles. However, if you keep a frog at home, and even if there are a pair of them, then for reproduction it is necessary to create ideal conditions, and corresponding to the type of frogs and their natural characteristics.

Phyllomedusa tree frog living in Brazil With the onset of spring, it builds nests very interestingly. A tree frog climbs a tree, makes its way onto a branch hanging over the water and selects the strongest leaf. Having climbed onto the leaf, the tree frog grabs its edges with its hind legs and bends them above itself. It turns out something like a bag. The tree frog lays its eggs in it. Caviar is so sticky that it sticks firmly to the sheet and also glues the sides of the sheet together, so that the bag from it does not come apart. The water that gets into the bag only promotes the development of the eggs; the tadpoles that emerge from the eggs of the tree frog fall directly into the water. When the tree frog cubs grow up, they fall from the nest straight into the river.

The tree frog is a blacksmith, which got its name for its peculiar sounds. It builds clay houses for its tadpoles, resembling hammer blows on iron. At the bottom of the pond, it collects dirt in the form of a ring with its paws. Then, with its paws equipped with suction cups, it collects clay and lays out the walls, smoothing the structure from the inside. The female builds the nest herself without the help of the male.

In two to three nights, the walls of the nest will appear 8-10 cm out of the water. The work stops, and the tree frog begins laying eggs. After about five days, tadpoles will emerge from the eggs, they are reliably protected from those who want to feast on them, by the walls of an artificially built pond, a kind of atoll in the pond. When the tadpoles grow up, the nest will be washed away by water, and they will jump out of it to freedom.

Marsupial tree frogs - nototremes, They carry their offspring like kangaroos. Only the leathery pouch of the frog nototrema is located not on the stomach, but on the back. The tree frog's skin seemed to burst along the spine and swell on both sides of the gap. How do baby tree frogs get there? And the male tree frog helps with this. With its hind paws, it pushes eggs into leathery pockets, eggs - there can be from a dozen to two dozen eggs. There, tadpoles will appear in the bag of eggs. Tadpoles may jump into the water when they appear, or they may remain in the bag for a long time, until frogs emerge from them. It all depends on the type of tree frog.

This spring I was looking at frog eggs in a ditch on the property and thinking about how I could show Masha how frogs emerge from eggs. But I was afraid that I would destroy the future “princes” and “princesses”)).

But now, thanks to this article, I am theoretically savvy, and next spring I will definitely set up a frog incubator at my dacha. We will watch how frogs are made from eggs.

The grass frog is the most common amphibian in the central zone of our country. It is painted greenish-brown with all sorts of stains. It usually lives in floodplains of rivers, in forests, and quite far from water bodies. It is most active at dusk and at night, and spends the day on the forest floor. During rain and cloudy weather, it can be found during the day. The grass frog feeds on all kinds of insects, mollusks, and worms, and they also eat those inedible species that birds avoid. They happily catch mosquitoes that try to drink her blood.

They are connected only with bodies of water in early spring(during the breeding season) and in winter. At the end of September they move to their native reservoir for the winter. They climb under a snag at the bottom of the pond and fall asleep until next spring. There was a time when there were a lot of grass frogs within Moscow, especially in the floodplains of rivers. Now there are significantly fewer of them. The reason is banal - the deterioration of the environmental situation.

Frogs are food for many animals and birds. They are happily eaten by foxes, badgers, martens, storks, owls and... even hedgehogs. Thus, the energy stored in small animals (insects, mollusks, bugs, worms) enters a higher trophic level through frogs.

***
Frogs are an interesting object for observing the development of an organism - from eggs to an adult animal. It’s a fascinating sight when before your eyes, in a fairly short time, a small frog turns out of caviar. If at someone’s home a child is interested in biology, nature can invite him to conduct such an experiment. Moreover, this biological “show” is, one might say, free. It will “occupy” the child for several months. To do this, they use frog caviar, which is collected in ponds, small lakes, and rivers.

The grass frog lays eggs at the end of April (at middle lane Russia) in shallow areas of ponds, ditches and puddles. IN southern regions- a bit earlier. The clutch is usually in the form of a slimy lump containing up to 1000 or more eggs. The eggs develop into tadpoles, and then into small frogs.

Experts noticed that twenty years ago the hatching of tadpoles from eggs within the city was almost one hundred percent. All the tadpoles were perfect. Recently, the hatching rate has sharply decreased; freaks began to appear among the tadpoles (one-eyed, with two tails, with one external gill, etc.), which ultimately died. Many tadpoles die without completing their development - turning into a small frog. All this is due to severe pollution of urban water bodies. However, for the sake of the child, you can go somewhere far from the city, where you can collect decent frog eggs in any body of water.

Frogs are interesting because any person (even a schoolchild) can hatch frogs from eggs at home and then release them into a pond. There is nothing complicated here, you just need to know some basic rules.

The spawning period for frogs begins in April and lasts about a week, after which adult individuals leave the pond and settle. And the caviar, accordingly, remains. Frogs return back to the pond only in the fall.

You need to take 1-2 lumps and place them in a small vessel (cup, basin) about 10 cm deep. After 1-2 days, embryos begin to develop from the eggs. At first, there will be small black dots inside the eggs (see picture), then something similar to a fish, and then you can see a creature inside the eggs that looks like a small tadpole.

After approximately 7-10 days (depending on water temperature), small tadpoles emerge from the eggs. On the sides of their heads they have branched external gills, with the help of which they breathe. During the first days, tadpoles stay on aquatic plants, attached to them with a suction cup. Soon they erupt a mouth, surrounded by horny jaws, with which they scrape off fouling leaves and pieces of the plants themselves.

I remember the incident. We lived at a biological station, cooked food in the kitchen, and washed dishes in the lake. That year there were a lot of tadpoles who “helped” us wash dirty dishes. They covered plates, pans, pots and ate leftover food. On such nutritious food, they grew quickly and left the pond much earlier (as it seemed to us) than the frogs from neighboring areas, which were not fed.

There must be a bush in the vessel aquatic plant, for example, Elodea, from which tadpoles scrape algae and bacteria. In laboratory conditions, tadpoles are fed with boiled eggs, dry milk, nettle infusion (small leaves are steamed with boiling water), and bread. They grow quickly on this food. However, it must be borne in mind that such food rots quickly, so it must be given little by little and removed periodically.

You can see how it progresses every day further development tadpoles. External gills do not last long. The tadpoles then develop gill slits with internal gills, like fish. He himself and outwardly becomes like a small fish. The tadpole retains this appearance for about a month. Then his hind limbs develop, and then his front limbs.

The lungs begin to develop, and the tadpole periodically rises to the surface to breathe with them. At this time, green leaves floating on the surface of the water should be placed in the vessel so that it is convenient for the tadpoles to climb out on them. His tail gradually becomes smaller, and his mouth, on the contrary, expands. Now the tadpole already resembles a frog in appearance. The baby frogs must be transferred to a vessel with high sides so that they do not escape. A similar incident happened at our house; we didn’t pay attention and the frogs scattered around the apartment. I had to get them out of all the corners and crevices.

At this time, the frogs do not eat anything. The size of such frogs reaches 2 cm; only a small tail reminds that this is a former tadpole. At this age they can be released into the reservoir, because... problems arise with feeding. At this time, they switch to animal food - they eat insects. But, if it is possible to grow small fruit flies, you can continue the process of observing small frogs. We had several large frogs living in our laboratory, which we fed with crickets (bought at a pet store).

Full development - from egg to frog - takes 2.5-3 months and depends on the water temperature and the quality of the food. Then the frogs begin a life full of dangers. They become adults only in the third year.

I immediately want to ask a question: what kind of fairy-tale frog princess was she? Most likely it was a grass frog. The tsars in Russia have always lived in the middle zone, but here only lake, pond, sharp-faced and grass frogs. The first two spend their entire lives in water and do not go far from bodies of water. And the frog princess, as you know, moved into the royal chambers. The sharp-faced frog is one and a half times smaller than the grass frog, and could hardly cope with an arrow, and its number is much smaller than the grass frog.

***
Observing the development of frogs is an amazing sight. It allows us to understand how a living being develops from an egg. Before your eyes (before the eyes of a child) the development of a living being occurs. Mammals, including humans, develop in approximately the same way. After all, they all swim in water before leaving their mother’s womb. These observations help to understand the origin of terrestrial vertebrates, which also includes amphibians.

Amphibians live on land and breed in water. Their tadpoles live here, similar to fish (both in appearance and in internal structure). Such similarities lead to the conclusion that amphibians and fish are related. The transitional form between fish and amphibians are lobe-finned fish, which were thought to have become extinct over 100 million years ago. However, in 1938 in Atlantic Ocean The first specimen of such a fish, which was named coelacanth, was caught off the southern coast of Africa.

***
So, dear parents, get your children a living “toy”, frog eggs, which will captivate the children for several months, and maybe for life.

***
Funds used to implement the project state support allocated as a grant in accordance with the order of the President Russian Federation dated March 29, 2013 No. 115-rp") and on the basis of a competition held by the Knowledge Society of Russia