The tadpole larva turns into a frog through. Life cycle and developmental stages of frogs. Development of frogs: photo
Frogs can breed when they reach four years of age. Waking up after hibernation, mature amphibians immediately rush to spawning waters, where they search for a partner that is suitable in size. The male has to perform various kinds of tricks in front of the female in order to get her attention, such as singing and dancing, showing off with might and main. After the female chooses a boyfriend 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 own species with a voice, namely a croak, which different types different: in one species it looks like a “trill” of a cricket, and in another it looks like the usual "qua-qua". You can easily find the voices of males on the Internet. The loud voice on the pond belongs to the males, while the voice of the females is very quiet or absent altogether.
Courtship
- Appearance and coloration.
Males of many species of frogs, for example, tropical poison dart frogs, change their color during mating season, becoming black. In males, unlike females, the eyes are larger, the sense organs are better developed and the brain is enlarged, respectively, and the front paws are decorated with so-called marriage calluses, which are necessary for mating so that the chosen one cannot escape.
- Dance
The attention of females can be attracted and various movements . Colostethus trinitatis just bounce rhythmically on a branch, and Colostethus palmatus get into exquisite poses when they see a female on the horizon, and other species that live near waterfalls manage to wave their paws at females.
Male Colostethus collaris 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 an upright position. If the female is not impressed by the performance, she raises her head, showing her bright yellow throat, this dares the male. If the female liked the male's dance, then she watches the beautiful dance, crawling to different places in order to better see the male's game.
Sometimes a large audience can gather: one day, while observing Colostethus collaris, scientists counted eighteen females that stared at one male and moved to another position in synchrony. Having danced, the male slowly leaves, while often turning around to make sure that the lady of the heart is following him.
In gold dart frogs, on the contrary, females fight for males. Having found a male who croaks, the female slaps her hind legs on his body and puts her front paws on him, she can 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 this type of amphibian had fights between both females and males for a partner they liked.
Fertilization or how frogs reproduce
Fertilization occurring externally
This type of fertilization occurs most often in frogs. The smaller male tightly clasps the female with his front paws and fertilizes the eggs spawned by the female. The male embraces the female in the amplexus posture, which there are three options.
- Behind the front paws of the female, the male makes a girth (sharp-faced frogs)
- The male grabs the female in front of the hind limbs (scaphiopus, spadefoot)
- There is a girth of the female by the neck (dart frogs).
Fertilization inside
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 the cloacae. In the same position, fertilization occurs in amphibians of the Nectophrynoides species, which first bear eggs, and then tadpoles in utero until the completion of the metamorphosis process and give birth to fully formed frogs.
Tailed male frogs of the genus Ascaphus truei have a specific reproductive organ.
During the breeding season, males quite often form specific mating rough calluses on their front paws. With the help of these calluses, the male clings to the slippery body of the female. Interesting fact: for example, in the common toad (Bufo bufo), the male climbs on the female far from the reservoir and rides on 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 lay eggs in it.
If the mating process takes place in water, the male can hold the spawned eggs by the female, pressing hind legs to have time to fertilize the eggs (species - Bufo boreas). Quite often, males can mix up and climb on males who clearly do not like it. The “victim” reproduces a specific sound and vibration of the body, namely the back, and forces you to get off yourself. Females also behave at the end of the fertilization process, although sometimes the male himself can release the female 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 their hind limbs.
Coition - amplexus
Types of amplexus
Frogs lay eggs, like fish, since caviar (eggs) and embryos lack adaptations for development on land (anamnia). Different kinds Amphibians lay their eggs in amazing places:
For the entire period of tadpole gestation, which lasts two months, the frog does not eat anything, while remaining active. During this period, she uses only internal stores of glycogen and fat, which is stored in her liver. After the frog's gestation process, the frog's liver decreases in size by a factor of three and there is no fat left on the abdomen under the skin.
After oviposition, most females leave their clutch, as well as spawning waters, and go to their usual habitats.
Eggs are usually surrounded by large gelatinous layer. The shell for eggs 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 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, clumps of eggs float to the surface of the 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 leaving the spawn tadpole falls into the water. Already after 5 days, having used up the supply of nutrients from the eggs, he will be able to swim and eat on his own. It forms a mouth with horny jaws. The tadpole feeds on protozoan algae and other aquatic microorganisms.
By this time, the body, head, and tail are already visible in tadpoles.
The head of the tadpole is large, 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 acts as a wire cutter when the tadpole feeds. Tadpoles have gills with gill openings. At the beginning of development, they are external, but in the process of development they change and attach to the gill arches, which are located in the pharynx, while already functioning as ordinary internal gills. The tadpole has a two-chambered heart and one circulation.
According to the anatomy, the tadpole at the beginning of development is close to fish, and having matured, it already resembles a reptile species.
After two or three months, the tadpoles grow back, and then the front legs, and the tail first shortens, and then disappears. At the same time, the lungs also develop.. Having formed for breathing on land, the tadpole begins its ascent to the surface of the reservoir to swallow air. Change and growth depend largely on hot weather.
Tadpoles feed primarily on food at first. plant origin, but then gradually pass to the food of the animal species. The formed frog can get ashore if it is a terrestrial species, or continue to live in the water if it is. aquatic view. The frogs that have come ashore are underyearlings. Amphibians that lay their 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 the laying of eggs to the end of the development of the tadpole into a full-fledged frog.
Amphibious poison dart frogs exhibit interesting behavior. After the tadpoles hatch from eggs, the female on her back, one by one, transfers them to the tops of trees into flower buds, in which water accumulates after rain. Such a 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 at about the third year of life.
After the breeding process green frogs stay in the water or keep on the shore near the reservoir, while brown go to land from the reservoir. The behavior of amphibians is largely determined by humidity. In hot, dry weather, brown frogs are mostly unobtrusive, as they hide from the sun's rays. But after sunset, they have hunting time. Since the green species of frog lives in or near water, they also hunt during daylight hours.
With the onset of the cold season, brown frogs move to the reservoir. 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.
After hibernation, frogs and toads go to shallow ponds, ditches, puddles and meltwater spills well warmed up by the sun. Here, the females spawn, very similar to fish eggs, and the males pour seminal fluid over it.
Caviar, as a rule, is laid a lot, with a margin, because from the stage of fertilization to the adult frog, countless dangers lie in wait for their offspring. Unfertilized eggs become white or opaque. If everything went well, you can observe the division of the yolk into two, then into four, into eight, and so on, until it looks like a raspberry inside the jelly. Soon the embryo begins to look more and more like a tadpole, moving little by little inside the egg.
On average, the egg stage lasts about 6-21 days, until the time when the larva hatches out. Most eggs develop in calm or stagnant waters to prevent mechanical damage to the eggs.
Tadpole
Immediately after hatching, the tadpole feeds on the remains of the yolk, which is located in its intestines. On this moment the amphibian larva has poorly developed gills, mouth and tail. This is a rather fragile creature. The tadpole initially attaches itself to objects in the water using small, sticky organs between its mouth and abdomen.
Then, 7-10 days after the tadpole has already hatched, it will begin to swim and feed on algae.
After 4 weeks, the gills begin to overgrow with skin until they eventually disappear.
Tadpoles get tiny teeth that help them scrape off algae. They have long had a spiral-shaped intestine, which makes it possible to extract the maximum amount of nutrients from the food they eat. At this time, the tadpole has a developed notochord, a two-chambered heart, and one circle of blood circulation.
Interestingly, by the fourth week, tadpoles can be considered quite social creatures. Some are even able to interact with each other like fish!
Tadpole with legs
After about 6-9 weeks, the tadpole develops tiny legs and begins to grow. The head becomes more pronounced and the body lengthens. Now large objects, such as dead insects or plants, can also serve as food for the tadpole.
The forelimbs appear later than the hind limbs, with the elbow being detected first.
After 9 weeks, the tadpole looks more like a small frog with a very long tail. The process of metamorphosis begins.
By the end of 12 weeks, the tail gradually disappears and the tadpole looks just like a miniature version of an adult frog. Soon he's out of the water to start adulthood. And after 3 years, the young frog will be able to participate in the process of reproduction.
Some frogs that live at higher altitudes or in colder places may take much longer to go through the tadpole stage. Others exhibit unique developmental stages that differ from the traditional tadpole-in-water life cycle type.
Is the life cycle of a toad and a frog different?
In fact, toads are the same frogs. Toads are just called differently, look a little different, but they are all part of the frog family. Many people are wondering what is the difference between the life cycle of toads and frogs. Perhaps the main difference will be that frog caviar looks like clots, and toad caviar looks like ribbons or stripes.
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 tadpole resembling a fish (even having gills), the “frog cub” quickly “transforms” into a completely new form to start leading radically new image life! 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 etc. 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 naturally- 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 have contributed new information into the genetic blueprint of any being.
What a frog looks like - everyone knows in the world. How is a frog born? Is it true that different types of frogs reproduce and care for their offspring in different ways?
In this article we will talk about how nature arranged the process of the birth of the most. As a rule, these amphibians are born in a pond or lake. The female frog leaves eggs only in stagnant water. After a certain period of time, tadpoles appear from the laid eggs, then they turn into small frogs ... this is how we used to think, looking at the frogs that live in our country, but in fact ...
In fact, not all frog species reproduce in the same way. The main "innovators" in the reproductive field are those frogs that live in the tropics. Firstly, the number of species of anurans we are talking about, in tropical zones exceeds all conceivable ideas. A large number of predators, who now and then want to eat frog eggs, makes these amphibians invent a variety of ways to save future offspring.
Birth of glass frogs
Females produce caviar, which looks like a gelatinous mass. This "mass" is attached to the back of the sheet (it is important that the sheet is located directly above the water). The father of the family becomes a guard for future offspring. When the tadpoles emerge from the eggs, they slide off the leaf directly into the pond and there is already a further transformation into an adult.
Birth of the South African frog
Have you heard of "foam houses"? This is not just an unusual substance, but a real hiding place in which South African frogs hide their eggs. How is foam formed? In order to create such a “house”, the female frog secretes a special substance, and the industrious male beats it into foam. Upper layer The foam house hardens and the eggs can comfortably continue to develop inside without fear of being eaten.
Birth of poison dart frogs
Poisonous South American frogs also give life to their offspring in an unusual way. They, like their other relatives, lay eggs (by placing them on moist soil). Then they carefully and very jealously guard the eggs. Well, when the tadpoles emerge from the eggs, they immediately climb onto their back to their parent. For what? To move from the ground to the tree. Having found the leaves of the bromeliad plant (which winds around the trees), the mother frog places the tadpoles in a funnel at the base of the bromeliad leaf (where water always accumulates after rains). Here the tadpoles find temporary shelter until their parent finds a nearby body of water and transfers them to it for later maturation.
Birth of the pygmy marsupial tree frog
Yes, yes, you heard right “marsupial”. By the way, the birth of cubs in this frog is similar to the way of reproduction in kangaroos. The frog has a special pocket made of leather, where the laid eggs are placed. Unlike the kangaroo, the tree frog has a pocket on its back. So a caring mother carries her future babies until the time comes for them to become tadpoles. Then the tree frog carries the future frogs to the reservoir and releases them.
The birth of the rain frog
The unusual structure of the eggs of these frogs makes it possible to be born not as a tadpole, but immediately as a small adult. The fact is that the internal composition of the egg is such that it has a sufficient supply of nutrients for the tadpole to feed and live to become a frog without leaving the egg shell.
Frogs are the most famous tailless amphibians. Occupy an intermediate position 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 the land. It is possible to assess the importance of amphibians in nature and human economic activity with further study of amphibians, whose biology has been developed only extremely superficially. The use of this animal for the study of biology gave recognition to the great merits of the frog in medicine.
Firstly, the lake frog is an exterminator of harmful animals. This representative of the amphibian order in its adult state feeds exclusively on animal food and, living in a wide variety of places, benefits by eating harmful insects. The importance of amphibians also increases because they eat insects in greater numbers than birds. bad smell and taste, as well as insects with a protective color. Particularly noteworthy is the fact that land species of amphibians hunt at night, when the vast majority of insectivorous birds are sleeping.
Secondly, amphibian frogs are a food base 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. Willingly eats amphibians and otters. Relatively often amphibians are found in the stomachs of badgers and black polecats. Finally, many commercial fish in lakes and rivers in winter period in large quantities they eat frogs, which turn out to be quite affordable mass food.
Of course, there are also negative aspects when frogs exterminate juvenile 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 the negative importance of amphibians in nature as guardians of dangerous infectious diseases, such as tularemia.
Thirdly, amphibians are evaluated as laboratory animals. The ease of dissection of the frog, suitable size and vitality have made it a favorite test subject for a long time. Most of the instruments of experimental medicine and biology are designed for this animal. The technique of physiological experiment is constantly 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 a year. This expense may be so great that it is necessary to take measures so as not to destroy all the animals. So, in England, frogs are now under the protection of the law, and catching them is prohibited.
Thus, the question arises about the relevance of growing 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 the stages of metamorphosis faster.
Research objectives:
1. Study the scientific literature on biology;
2. Identify the causes of positive and negative influences environment for development;
3. Conduct research work.
Object of study: caviar of an ordinary frog.
Hypothesis: Various environmental conditions affect the development of a frog from spawn to individual in an unnatural habitat. If you create all the necessary conditions, then you can achieve the maximum percentage of survival of tadpoles.
Reliability of results provided by the personal participation of the author in the research process.
lake frog
Description
The lake frog is a species of tailless amphibians of the family of real frogs. The lake frog is the largest species of amphibian fauna of Russia: its body length can reach up to 150 mm.
Tailless - the largest order of amphibians, numbering about 6000 modern and 84 fossil species. Often, representatives of the order are called frogs, but the use of this term is complicated by the fact that only representatives of the family of real frogs are called frogs in the narrow sense. Tailless amphibian larvae are tadpoles.
Class - Amphibians, detachment - 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 tympanic membrane. The skin of the frog is slimy and smooth to the touch, its epidermis does not keratinize. There is a marble-like pattern on the dark belly. Calcaneal inner 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, males have a skin thickening - a callus, which grows during mating.
Amphibians require oxygen to live. The frog can get it on land and partially under water through the skin. The respiratory organs of amphibians, which include frogs, are lungs, skin and gills. Unlike tadpoles, which are aquatic, adult frogs do not have gills. Oxygen dissolved in water enters the blood of these creatures through the skin. This way of breathing can provide the body with the necessary gas only if the frog is in a state of hibernation.
A frog can be under water for a long time, because. she has very large lungs. Before diving, the animal gains full lungs of air. Under water, oxygen is absorbed very slowly through the blood arteries, and this helps the frog to stay under water for a long time. As soon as the air supply runs out, the animal quickly emerges and keeps its head above the surface of the water for some time in order to regain full lungs of air.
Frogs never drink. Fluid enters their body through the skin.
An 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 the main diet. In gardens located in the lowlands near water bodies, fruit trees, shrubs and vegetable crops are almost never affected by pests, since frogs are cleaning animals. Only a few frogs are capable of destroying hordes of insect pests.
The breeding season is April - early May. Reproduction occurs in puddles, reservoirs, lakes, canals, in any shallow reservoir. Spawning begins 3-5 days after awakening. Males appear on the reservoirs earlier, they sing mating songs, inviting females. Having spawned, the common frog does not linger in the reservoir and disperses to 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 in clusters of a rather significant size, and sometimes in cords; a lot of them are put off. 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,
Hearts were given to science.”
L. Gainulina
Lake frogs are often caught as laboratory animals for scientific, medical and educational institutions.
For example, students of the Orenburg State Pedagogical University use up to 3,000 lake frogs to conduct workshops in physiology and zoology in one year of study.
A lot of biologically active substances have been found in frogs, but they have been studied much less than toads.
It has long been known that if you put a frog in milk, then it will not turn sour for a very long time. Modern research has confirmed the antimicrobial properties of the mucus that covers the skin of the frog. This prevents the reproduction of sour milk bacillus.
It was possible to extract a number of substances with biological activity from the skin of different types of frogs.
Some of these substances are effective in killing bacteria, while others have vasodilating properties. From the skin of the white Australian tree frog, a substance was isolated that has a choleretic effect, as well as stimulating the secretion of gastric juice. From this substance it is possible to make a drug for the treatment of certain mental illnesses.
In the skin of one of the species of frogs, dermorphins were found, which are 11 times more analgesic than morphine.
Frog neurotoxins are among the most powerful. Batrachotoxin, isolated from the Colombian frog, locally called "cocoi", 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 investigated.
The antimicrobial and wound-healing properties of frog caviar have received scientific confirmation - the substance ranidon, which has a high bactericidal activity, has been isolated from the shell of the caviar.
No matter how we feel about frogs, this is one of the most common, frequently used laboratory animals, along with rats and mice. For example, the clawed frog was the first cloned animal, and not Dolly the sheep, as we used to think. In the 1960s, the English embryologist Gurdon cloned tadpoles and adult frogs.
For merits 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 merits of these animals in the development of science. So scientists thanked their unwitting helpers in many important scientific research and discoveries. The experiments of the Italian physicists of the XVIII century Luigi Galvani and Alessandro Volta, carried out on frogs, led to the discovery of galvanic current. A huge number of experiments on frogs were carried out by the physiologist Ivan Sechenov. In particular, he used them in the study of the nervous activity of animals. And the frog's heart turned out to be an interesting object for the study of cardiac activity. The French physiologist Claude Bernard, who was also helped to make a number of discoveries by frogs, expressed the idea of erecting a monument to him. And at the end of the 19th century, the first monument to frogs was opened at the Sorbonne (Paris University). And the second was erected by medical students in Tokyo in the 60s of the XX century, when the number of frogs they used for science reached 100 thousand.
In addition to scientific value, these amphibians have practical value. So 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, getting started:
07.05.15 caviar was taken in a pond, surrounded by shrubs and aquatic plants.
The shell of each egg is swollen, similar to a gelatinous transparent layer, inside which an egg is visible. The upper half is dark and the lower half is light.
In nature, the rate of development of eggs depends on the temperature of the water. 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 caviar: the water temperature is room temperature, warm.
After 8-10 days, tadpoles hatch from the eggs, more like fish fry. Passive, do not eat. Apparently there is enough nutritional reserve of eggs. There are gill openings and gills.
05/23/15 Noticeable metamorphosis. The tadpoles began to feed on their own, move actively, and keep close to each other. They scurry in different directions, but do not swim far, and the whole flock moves almost simultaneously. The average size of tadpoles is approximately 7-8 mm.
By this time, the head, torso, and tail are already visible. The head is large, there are no limbs, the tail section of the body is a fin, there is also a lateral line, and the oral cavity looks like a sucker. The gills are initially external, attach to the gill arches located in the pharynx, and already function as true internal gills.
The suction cup is located below the mouth (it can be used to determine the type of tadpole), after a few days the gap of the mouth along the edges is overgrown with some kind of beak, which works like wire cutters 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 resemble reptiles.
In nature, sometimes tadpoles form huge clusters - up to 10,000 in one cubic meter of water. Not without reason, among the ancient Egyptians, the image of a tadpole meant the number 100,000, that is, “a lot”. 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 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 area of direct sunlight (balcony) - 25 pcs.
We place an absolutely transparent glass container (3 l) in a well-lit area, in a warm place in the area of direct sunlight (balcony) - 10 pcs.
We place a dark, opaque container (5 l) in a warm place, slightly shaded, but with enough 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 caviar collection site, i.e. closest to the breeding conditions, as well as algae and grass. Microorganisms are observed in the water.
Within two days, no differences in behavior are observed. All tadpoles are mobile, hiding in mud and grass, and actively react to sound and movement. They feed on plant foods during the day, as if biting off, and also scrape off plaque from the surfaces. Periodically rise to the surface of the water and swallow air. Growth rates are not striking, as you know, they average 0.6 mm per day.
05/25/15 In the glass container, located in the zone of direct sunlight, by the evening all the tadpoles died. At the same time, without preserving the contours of the body, almost completely decomposed and disappeared. Outwardly, the surface of the water in the container looked like it had bubbled up, as if sour.
Conclusion: tadpoles, despite the assertion that complete metamorphosis occurs faster with more high temperatures(21-26 C), and on average it lasts 50-90 days, do not tolerate direct sunlight.
We cover a completely transparent plastic container with paper, protecting it from the sun.
05/28/15 In a plastic container, even though it is not under direct sunbeams, tadpoles are passive, are practically without movement. The water is very hot. Several pieces died. Move to a more shady spot.
In other containers, tadpoles are still active. They are in constant motion and feeding.
The growth of tadpoles is already more noticeable. The average is about 10 mm.
We add fresh water and algae from the reservoir, but not from the place of masonry, to all containers with tadpoles.
06/01/15 In a transparent, well-transmitting daylight 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 are clearly visible, the marble pattern of the body.
In an opaque container that practically does not let in daylight, but located in a warm place, the growth of tadpoles is practically not noticeable, as well as 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 a large mortality during the development period, even in the absence of external predators feeding on tadpoles.
Within 3 weeks with constant feeding and changing the 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 about 20-25 mm.
The highest mortality was in a transparent container located in a warm place. Perhaps from a constant drop in water temperature: from very warm, heated by the sun during the day, to very cold at night.
06/27/15 The tadpole in the garage underwent visible metamorphoses: hind legs appeared.
07/03/15 Within 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 turns out to be smaller size than was the tadpole from which it had just evolved.
Thus, as in nature, about 2-3 months pass from the moment of laying eggs to the end of the transformation of a tadpole into a frog.
Frog metamorphosis: 1 - eggs (caviar), 2 - tadpole with external gills, 3 - without gills, 4 - with hind legs, 5 - with all legs and tail, 6 - frog.
The most successful of the tadpoles survive to the stage of metamorphosis and turn into a yearling frog. Underyearlings are very voracious. The volume of their stomach in a full state exceeds one fifth of the total weight. There is one interesting detail: if there is not enough animal food in the reservoir, the herbivorous tadpole winters in the larval stage, postponing the transformation from a vegetarian into a predator 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 you know, in nature, tadpoles feed on algae, plant matter, and larvae of small microorganisms. In captivity, perhaps due to the lack of 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 the sufficiently large number of hatched tadpoles, 11 survived. At the same time, 5 out of 30 - in a dark, opaque container (5 l), located in a room slightly shaded, without direct sunlight.
3 out of 10 - in a light, opaque container (2 liters), located in a poorly lit, cool place in the garage. At the same time, a frog was formed ahead of all.