The development of a frog from spawn to individual in an unnatural habitat under different environmental conditions. Frog breeding and care All steps are interconnected

• HAPPY BIRTHDAY, FROG!
• The birth of a frog most often occurs in ponds, lakes and other stagnant water bodies, because. This is where adult animals lay their eggs.

• Happy birthday, frog!

  Happy birthday, frog!
• Soon, tadpoles emerge from the eggs, which after a while will turn into frogs.
• You can read more about this.
• But this is all true only for our ordinary species, and in tropical rainforests, where the number of species even in a small area is in the tens, everything is completely different.
• Where frogs are visible or invisible, hunters for themselves, eggs and tadpoles will definitely appear. What to do? How to protect your offspring? To protect their eggs from voracious predators, some frogs have adapted to lay their eggs on land.
• THE BEST INVENTIONS OF NATURE.
• The female "glass" frog places eggs in the form of a gelatinous mass on the lower surface of a leaf hanging over a pond.
• The male guards the clutch until tadpoles appear. Coming out of the eggs, they slide off the leaf and fall into the water, where the transformation soon takes place - the birth of a frog.

• Glass frog caviar

  
  Glass frog caviar
• Mother nature is arranged in such a way that no living creature can find an absolutely reliable way to protect itself from predators.
• And yet, caviar laid on leaves or the ground is less dangerous than placed in water.
• To confuse predators, many species of tropical frogs spawn in the most unexpected places.
• FOAM HOUSE.
• South African frogs make a foam house for their offspring. When it comes time to spawn, they gather on the branches of trees hanging over any body of water.
• Females secrete a special viscous liquid onto a branch, and males beat it into foam, working with their hind legs. In such a foamy nest, the females lay their eggs to continue their kind and give birth to babies. The outer layers of the foam dry up, and the laid caviar is protected from all sorts of troubles.

• foam house

  
  foam house
• Despite the seeming unreliability, the foam house is one of the best inventions in the animal world. Firstly, the foam smooths out changes in temperature and humidity, and secondly, it does not arouse suspicion among predators: there is hardly anything edible hiding inside.
• After a few days, tadpoles hatch from the laid eggs, the nest begins to disintegrate, they go outside and fall into the water, where the frog is then born.
• This method of survival is used not only by frogs, but also by many insects - leafhoppers, grasshoppers and.
• YOUR POOL.
• And the South American poison dart frogs (familiar for their poisonousness) have adapted to carry the cubs on their backs. First, they lay their eggs on moist soil and jealously guard future offspring. Then, the hatched tadpoles sit on the back of the parent and the adult frog climbs the tree with its burden.

• Own pool

  
  Own pool
• But why? She is looking for bromeliad - a plant that attaches to a tree, where the leaves form a funnel at the base, where water collects during the rains, and a semblance of a small pond forms high in the branches. When the poison dart frog finds a suitable body of water, the tadpoles unhook and fall into the water.
• It is not easy for predators to get into such a shelter, and tadpoles can easily develop.
• LIKE A KANGAROO?
• The pygmy marsupial tree frog has a completely unusual way of giving birth to offspring. The laid eggs develop in a special skin pocket in the protrusions on the back of the female. Here, future babies are protected from enemies and from drying out.
• When the time comes for the birth of tadpoles, the female finds the same bromeliad and descends into the water. Water penetrating into the bag serves as a signal for tadpoles to go outside.

• marsupial tree frog

  
  marsupial tree frog
• One of the species of marsupial tree frogs also has a skin fold - like a kangaroo pouch - only located backwards. When laying eggs, the mother frog puts them in her pocket with her hind legs and the hatched tadpoles remain there.
• Only when they turn into frogs do they leave their safe haven.
• MIRACLE CAVIAR.
• The birth of a rain frog occurs in its own way: the female lays her eggs on the forest floor - in the moss, under rotten leaves, by the stream, where there is no danger of drying out.
• The eggs of this frog (compared to others) are of enormous size with a supply of nutrients.

• Miracle caviar

  Miracle caviar
• Therefore, the tadpole can stay in the egg longer than usual - after all, he does not have to take care of his food.
• Without leaving the egg, the tadpole turns into a small, fully formed frog, ready for adulthood.
• TAKEN AND SWALLOWED!
• But Darwin's tree frog literally swallows her offspring, but not in order to eat, but in order to protect future frogs.

• Darwin's tree frog with a newborn

  
  Darwin's tree frog with a newborn
• The female lays her eggs on the ground, and the male sits down to guard her, and as soon as the tadpoles are about to come out, he places the eggs in a special pocket in the throat.
• They stay there until they turn into little frogs, and then they get out and begin an independent life.
• So, in a completely different way, the birth of a frog occurs.

Among many animals, only the so-called invertebrates reproduce asexually. Vertebrate animals - such as mammals, fish, reptiles, birds and amphibians - reproduce sexually: spermatozoa and eggs, which carry hereditary material typical for this species, are combined during fertilization. A fertilized egg is called an embryo.

Depending on the type of animal, the embryo can develop both in the mother's body and outside it. Gradually, little cubs develop from fertilized eggs in accordance with the genetic guidelines laid down in it. Many, like frogs, go through another developmental stage before becoming fully grown.

From egg through larva to adult

Snails live on land, in running water and in the seas. Sea slugs lay their eggs in sea water, which, after high tide, get stuck between the rocks. The fertilized eggs hatch into larvae (veligers) that can swim. They swim with the current and finally sink to the rocky bottom, where they turn into adult crawling clams.

fertilized egg

The red spot in the middle of the egg yolk is a three-day-old chicken embryo. A week later, the embryo already takes the form of a chicken. A month later, the chick is already fully developed and covered with soft fluff. With an egg tooth on his beak, he breaks the egg shell and comes out into the light. The chick is hatched and becomes an adult without any additional developmental stage.

From egg to tadpole

During the mating season, many frogs gather in large noisy groups. Females respond to loud calls from males. Only a few species of frogs give birth to live young; most species lay their eggs (spawn) in or near water. The number of eggs depends on the type of frog and ranges from one to twenty-five thousand. As a rule, the eggs are fertilized outside the body of the frog and left to their own devices. When the egg matures, a small tadpole hatches from it. Tadpoles live in water and breathe through gills like fish. Only in a few species of frogs do females take care of their offspring.

Frogs and toads

Unlike adult frogs, tadpoles are herbivorous and feed on aquatic plants and algae. After a certain time, an amazing transformation (metamorphosis) occurs in the development of the tadpole: the fore and hind limbs appear, the tail disappears, the lungs and eyelids develop, as well as a new digestive system designed to digest animal food.

The rate of transformation is different in different species, the main factor here is the temperature of the water. In some toads and frogs, metamorphosis occurs in a few days or weeks, while in others it takes several months. The tadpole of the North American bullfrog does not fully develop until after a year or more.

Frogs and toads belong to the class of amphibians and to the same group of anurans, but differ in appearance and lifestyle. Frogs have soft skin and are good jumpers, while toads are covered in warts and tend to crawl. There are over 3,500 species of frogs and toads on earth. With the exception of Antarctica, they can be found on every continent. They prefer to live in tropical and subtropical zones, where more than 80% of all species live. But wherever they live, in deserts or mountains, savannahs or tropical rainforests, they must return to the water in order to procreate.

What is metamorphosis

In their development, frogs go through three stages: from an egg to a tadpole, and then to an adult frog. This process of development is called metamorphosis. Many invertebrates also pass through the stage of larvae in their development. However, the most amazing changes occur in the life of insects: butterflies and beetles, flies and wasps. Their life is divided into four stages, very different from each other in terms of nutrition and habitat: egg, larva, pupa, adult insect. The larva looks completely different from the adult insect and has no wings. Her life is completely focused on growth and development, and not on procreation. Only after the larva pupates does it become an adult insect.

Frogs, gametogenesis, fertilization and other seasonal activities depend on numerous external factors. The life of almost all amphibians depends on the number of plants and insects in the pond, as well as the air and water temperature. Different stages of development of frogs are distinguished, including the larval stage (egg - embryo - tadpole - frog). The metamorphosis of a tadpole into an adult is one of the most striking transformations in biology, as these changes prepare an aquatic organism for terrestrial existence.

Development of frogs: photo

In tailless amphibians, such as frogs and toads, metamorphic changes are most pronounced, almost every organ undergoes modification. The shape of the body changes beyond recognition. After the appearance of the hind and forelimbs, the tail gradually disappears. The cartilaginous skull of the tadpole is replaced by the facial skull of the young frog. The horny teeth that the tadpole used to eat pond plants disappear, the mouth and jaws take on a new shape, the muscles of the tongue develop more strongly to make it easier to catch flies and other insects. The elongated large intestine characteristic of herbivores shortens to accommodate the adult's carnivorous diet. At a certain stage in the development of frogs, the gills disappear, and the lungs increase.

What happens immediately after fertilization?

Soon after, it begins to move from one cell stage to another in the process of division. The first cleavage starts at the animal pole and runs vertically down to the vegetative pole, dividing the egg into two blastomeres. The second cleavage occurs at right angles to the first, dividing the egg into 4 blastomeres. The third furrow is at right angles to the first two, being closer to the animal than to the vegetative pole. It separates the top four small pigmented areas from the bottom four. At this stage, the embryo already has 8 blastomeres.

Further splits become less regular. As a result, a unicellular egg gradually turns into a unicellular embryo, which at this stage is called a blastula, which, at the stage of 8-16 cells, begins to acquire spatial cavities filled with liquid. After a series of changes, a single-layer blastula turns into a two-layer embryo (gastrula). This complex process is called gastrulation. The intermediate stages of frog development at this stage involve the formation of three protective layers: ectoderm, mesoderm and endoderm, which are also known as primary. Later, larvae hatch from these three layers.

Tadpoles (larval stage)

The next after the embryo is the larva, which leaves the protective shell already 2 weeks after fertilization. After the so-called release, the frog larvae are called tadpoles, which are more like small fish about 5-7 mm long. The body of the larva includes a distinct head, trunk and tail. The role of the respiratory organs is played by two pairs of small external gills. A fully formed tadpole has organs adapted for swimming and breathing; the lungs of the future frog develop from the pharynx.

Unique Metamorphoses

The aquatic tadpole undergoes a series of changes that eventually transform it into a frog. During metamorphosis, some larval structures are reduced and some are changed. Metamorphoses initiated by thyroid function can be divided into three categories.

1. Changes in appearance. Rear limbs grow, joints develop, fingers appear. The forelimbs, still hidden by special protective folds, come out. The tail shrinks, its structures break down and gradually nothing remains in its place. The eyes from the sides pass to the top of the head and become bulging, the lateral line organ system disappears, the old skin is shed, and a new one, with a large number of skin glands, develops. The horny jaws fall off along with the larval skin, they are replaced by true jaws, first cartilaginous and then bony. The gap in the mouth increases significantly, allowing the frog to feed on large insects.

2. Changes in internal anatomy. The gills begin to lose their importance and disappear, the lungs become more and more functional. Corresponding changes occur in the vascular system. Now the gills gradually cease to play a role in blood circulation, more blood begins to flow into the lungs. The heart becomes three-chambered. The transition from a predominantly plant-based diet to a purely carnivorous diet affects the length of the alimentary canal. It shrinks and twists. The mouth becomes wider, the jaws develop, the tongue enlarges, the stomach and liver also become larger. The pronephros is replaced by mesospheric buds.

3. Lifestyle changes. During the transition from larva to adult stage of development of frogs, with the onset of metamorphosis, the lifestyle of an amphibian changes. It often rises to the surface to gulp air and inflate the lungs.

Frog - a miniature version of an adult frog

From the age of 12 weeks, the tadpole has only a small remnant of the tail and looks like a smaller version of the adult, which, as a rule, completes a full growth cycle by 16 weeks. The development and species of frogs are interrelated, some frogs that live at high altitudes or in cold places can live in the tadpole stage all winter. Certain species may have their own unique developmental stages that differ from the traditional ones.

Frog life cycle

Most frogs breed during the rainy season, when ponds are flooded with water. Tadpoles, whose diet differs from that of adults, can take advantage of the abundance of algae and vegetation in the water. The female lays eggs in a special protective jelly under water or on plants located nearby, and sometimes does not even care about the offspring. Initially, the embryos absorb their yolk reserves. Once the embryo has turned into a tadpole, the jelly dissolves and the tadpole emerges from its protective shell. The development of frogs from eggs to adults is accompanied by a number of complex changes (appearance of limbs, reduction of the tail, internal restructuring of organs, and so on). As a result, the adult individual of the animal in its structure, lifestyle and habitat differs significantly from the previous stages of development.

The frog turns into a prince only in a fairy tale. But don't the transformations that a frog undergoes during its life cycle demonstrate evolution? From a fish-like tadpole (which even has gills), the “baby frog” quickly “transforms” into a completely new form to start leading a radically new lifestyle! The mouth becomes wider, the tail dissolves, but an "elastic" tongue is formed for catching flies, and nostrils appear, and bulging eyes move to another place on the head. Finally, when the lungs finally mature and four legs grow, this matured tadpole celebrates its “coming of age” by jumping out of the water to now live on land.

This amazing transformation (metamorphosis) is far from being just external. Almost all organs and systems of the body undergo a radical restructuring. For example, a complete reconfiguration of the nervous system is needed to control new or reprogrammed organs - eyes, ears, paws, tongue, etc. A similar reorganization must also take place at the biochemical level. Changes in hemoglobin in the blood, light-sensitive pigment in the eyes, among many other changes. Even the excretory (excretory) system of the frog is changing in order to fit the new way of life.

Biologists are puzzling over the mega-complexity of this "rebirth" that occurs in ordinary ponds. A frog basking on a water lily leaf is an amazing result of many changes occurring sequentially with amazing accuracy in the right order. It would not be an exaggeration to say that the opening ceremony of the Olympic Games simply pales in comparison to the "choreography" of the frog's metamorphosis process. The life of a tadpole would certainly become more difficult if, for example, its tail disappeared before the legs grew. The same applies to his internal organs, bones, nervous system, biochemical processes, and so on. Any failure can stall the entire process of reorganization of the organism ... and lead to rather unfortunate results (for a tadpole)!

photolibrary.com

Very difficult program

The fantastically complex information encoded in the DNA that allows a tadpole to turn into a frog clearly points to the Higher Intelligence that created it. Such a program cannot be formed in a natural way - it demonstrates the originally intended end result.

All steps are interconnected

Years of research have uncovered several levels of processes required to effect this "transformation of life." For example, the disappearance of the tail requires a precisely programmed execution of micrologistics operations. First, the tadpole stops the formation of tail muscle cells. It then produces a series of highly specific enzymes that dissolve tail cells.

Then, at the right moment, these "little killers" are combined and injected into tail cells of all types. Finally, roaming macrophages engulf these dead cells so that they can then reuse their components and nutrients in other parts of the body (i.e., the tail is not shed, but reabsorbed by the body).

"Change" does not mean "evolve"

So how justified is the assertion that this is an example of " evolution in action"? Is the transformation of a tadpole into a frog a good example of evolution?

Quite the opposite! Although the tadpole may look like a real "fish" in appearance, it is a frog from its very birth. Everything that he needs for rebirth (that is, all genetic information, schemes and programs) is already embedded in the DNA code stored in the nuclei of the tadpole's cells. At this micro level, we find not only a complete plan for the development of a frog, but also a fully functional factory with all the necessary mechanisms and equipment to bring this plan to life.

The genome of a fish does not contain the information needed to become an amphibian, and there is nowhere for it to get such information from.

This embedded information is the key difference between the evolutionary tale (as if a fish evolved into an amphibian) and the real world (in which a tadpole turns into a frog). From the very moment of its birth from an egg, the tadpole is already equipped with a complete set of instructions "how to turn into a frog on your own." In contrast, fish only contain the genetic instructions for "building"... fish! The genome of a fish does not contain the information needed to become an amphibian, and there is nowhere for it to get such information from. In fact, it is doubtful that there is even one undisputed example of how evolutionary mechanisms introduced new information into the genetic blueprint of any creature.

This spring, I looked at frog eggs in a ditch on the site and thought about how to show Masha how frogs emerge from eggs. But I was afraid that I would ruin the future "princes" and "princesses")).

But now, thanks to this article, I am theoretically savvy, and I will definitely arrange a frog incubator in the country next spring. We will observe how frogs are obtained from eggs.

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

They are associated with water bodies only 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 the next spring. There was a time when there were a lot of common frogs within Moscow, especially in floodplains. Now they have become much less. The reason is banal - environmental degradation.

Frogs are food for many animals and birds. Foxes, badgers, martens, storks, owls and ... even hedgehogs eat them with pleasure. Thus, the energy stored in small animals (insects, mollusks, bugs, worms) is delivered to a higher trophic level through frogs.

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Frogs are an interesting object of observation of the development of the organism - from caviar to an adult animal. This is a fascinating sight, when a small frog turns out of caviar before your eyes in a fairly short time. If someone at home has a child who is fond of biology, nature, he can be offered to conduct such an experiment. Moreover, this biological "show" can be said to be free. It will "occupy" the child for several months. For this, frog caviar is used, which is collected in ponds, small lakes, and rivers.

The common frog lays eggs at the end of April (in central Russia) in shallow areas of ponds, ditches and puddles. In the southern regions - a little earlier. The clutch is usually in the form of a slimy lump containing up to 1000 or more eggs. Tadpoles develop from eggs, and then small frogs.

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

Frogs are interesting in that any person (even a schoolboy) can bring frogs out of their eggs at home, in order to then release them into a pond. There is nothing complicated here, you just need to know some elementary rules.

The period of spawning in frogs begins in April and lasts about a week, after which adults leave the reservoir and settle. And the caviar, respectively, remains. Frogs return to the pond only in autumn.

It is necessary 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. In the beginning, these will be small black dots inside the eggs (see picture), then something similar to a fish, and then you can already see a creature that looks like a small tadpole inside the eggs.

After about 7-10 days (depending on the temperature of the water), small tadpoles emerge from the eggs. On the sides of the head, they have branched external gills, with which they breathe. The first days the tadpoles stay on aquatic plants, attaching to them with a sucker. Soon, their mouth is cut through, surrounded by horny jaws, with which they scrape off the fouling leaves and pieces of the plants themselves.

I remember a case. We lived at the 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 the dirty dishes. They stuck around plates, pans, pots and ate leftover food. On such a nutritious food, they grew rapidly and left the reservoir much earlier (as it seemed to us) than the frogs from neighboring areas, which were not fed.

The vessel must contain a bush of an aquatic plant, for example, elodea, from which tadpoles scrape off algae and bacteria. Under laboratory conditions, tadpoles are fed boiled eggs, milk powder, nettle broth (small leaves are steamed with boiling water), bread. On such food they grow quickly. However, it must be borne in mind that such food quickly rots, so it must be given little by little and periodically removed.

You can observe daily how the further development of tadpoles proceeds. External gills do not last long. The tadpoles then develop gill slits with internal gills, similar to fish. He himself and outwardly becomes like a small fish. This type of tadpole retains about a month. Then he develops the hind limbs, and then the front ones.

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 would be convenient for the tadpoles to climb onto them. His tail gradually decreases, and his mouth, on the contrary, expands. Now the tadpole already looks like a frog. The frogs must be transferred to a vessel with high sides so that they do not run away. A similar incident occurred at our house, they overlooked it and the frogs scattered around the apartment. I had to get them out of all the nooks and crannies.

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 pond, because. there are problems 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. Several large frogs lived in our laboratory, which we fed crickets (bought at a pet store).

Full development - from eggs to frogs - takes 2.5-3 months and depends on water temperature and food quality. Further, 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 fabulous frog princess was she? Most likely, it was a common frog. Tsars in Russia have always lived in the middle lane, and only lake, pond, moor and common frogs live here. The first two - spend their whole lives in the water and do not go far from the reservoirs. And the frog princess, as you know, moved to the royal chambers. The sharp-faced frog is one and a half times smaller than the grass frog, and could hardly cope with the arrow, and its number is much less than the grass frog.

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

Amphibians live on land and breed in water. Their tadpoles, similar to fish, also live here (both in appearance and in internal structure). This similarity leads to the conclusion about the relationship of amphibians and fish. A 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 the Atlantic Ocean off the southern coast of Africa, the first specimen of such a fish was caught, which was named coelacanth.

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So, dear parents, get your children a living "toy", frog caviar, which will captivate the children for several months, and maybe for life.

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When implementing the project, state support funds were used, allocated as a grant in accordance with the Decree of the President of the Russian Federation of March 29, 2013 No. 115-rp) and on the basis of a competition held by the Knowledge Society of Russia