It seems to almost all of us that we can define any concept from the curriculum of a comprehensive school without any problems. For example, amphibians are frogs, turtles, crocodiles and similar representatives of the flora. Yes, that's right. We can name some representatives, but what about describing their characteristics or lifestyle? For some reason, they were singled out in a special class? What is the reason? And what is the rule? This one, you see, is more difficult.
How will they surprise us?
It is likely that the respiratory system of amphibians is different from a similar internal structure, say, mammals or reptiles. But what? Are there similarities between us and them? We will try to answer all these questions in this article. However, it is worth paying attention to the fact that in the process of studying the material, the reader will not only learn about how amphibians are similar to each other (turtles and crocodiles tothey, by the way, do not apply), but also get acquainted with the most interesting facts related to these animals. We bet you didn't even know something. Why? The thing is that a paragraph of a school textbook does not always provide the full range of knowledge.
General information about the class
The class Amphibians (or Amphibians) represents primitive vertebrates whose ancestors changed their habitat more than 360 million years ago and left the water for land. Translated from ancient Greek, the name translates as “living a double life.”
It should be noted that amphibians are cold-blooded creatures with a variable body temperature, depending on environmental conditions.
In the warm season, they are usually active, but when cold weather sets in, they hibernate. Amphibians (frogs, newts, salamanders) appear in the water, but spend most of their existence on land. This feature can be called almost the main one in the life of this species of living beings.
Species of amphibians
In general, this class of animals includes more than 3000 species of amphibians, represented by three groups:
- tailed (salamander);
- tailless (frogs);
- legless (worms).
Amphibians appeared in places with a temperate and hot climate. However, to this day they live there.
Basically, they are all small in size and have a length of no more than one meter. Exceptionis a giant salamander (the main signs of amphibians seem to be blurred in it), living in Japan and reaching a length of up to one and a half meters.
Amphibians spend their lives alone. Scientists have established that this did not happen as a result of evolution. The first amphibians led exactly the same way of life.
Among other things, they are excellent camouflage by changing their color. By the way, not everyone knows that poison secreted by special skin glands also serves as protection against predators. Perhaps only reptiles, arthropods and amphibians have this feature. Mammals with such a set of characteristic features are not found in nature. In fact, it’s hard to even imagine how, for example, a cat familiar to all of us could adjust its own body temperature depending on changes in the environment or secrete poison, defending itself from an attacking dog.
Features of the skin
All amphibians have a smooth, thin covering of skin rich in skin glands that secrete mucus necessary for gas exchange.
The secreted mucus also prevents the skin from drying out and may contain poisonous or signaling substances. The multi-layered epidermis is abundantly supplied with a network of capillaries. Most venomous individuals can take on bright colors as a defense and warning device against predators.
In some amphibians of the anurans group, keratinized formations are found on the upper layer of the epidermis. This is especially developed in toads, which have morehalf of the skin surface is covered with a stratum corneum. It is important to note that the weak keratinization of the cover does not prevent the penetration of water through the skin. This is how the breathing of amphibians is arranged, which are able to breathe under water only with their skin.
In terrestrial species, keratinized skin can form claws on the limbs. In tailless amphibians, the entire subcutaneous space is occupied by lymphatic lacunae - cavities where a supply of water accumulates. And only in a few places is the connective tissue of the skin connected to the muscles of the amphibian.
Amphibian lifestyle
Amphibians, photos of which can be found in all zoology textbooks without exception, undergo several stages of development: those born in water and resembling fish, as a result of transformation, acquire pulmonary respiration and the ability to live on land.
This development is not found in other vertebrates, but is common in primitive invertebrates.
They occupy an intermediate position between aquatic and terrestrial vertebrates. Amphibians live (fish in this regard are more adapted representatives of the fauna) in all parts of the world where there is freshwater, with the exception of cold countries. Most of them spend half their lives in water. Others have adults living on the ground, but in places with high humidity and near water.
During a drought, amphibians (birds might envy such a feature) fall into suspended animation, burrowing into the silt, and in cold weather, in temperate zones, they are prone tohibernation.
The most favorable habitats are tropical countries with moist forests. Least of all, amphibians prefer arid corners of nature (Central Asia, Australia, etc.).
These are aquatic and terrestrial inhabitants, usually preferring a nocturnal lifestyle. The day is spent in hiding or half asleep. Tailed species move on the ground similarly to reptiles, and tailless species move in short jumps.
Amphibians are animals that are generally able to climb trees. Unlike reptiles, adult male amphibians are very vociferous; when young, they are silent.
Nutrition in most cases depends on age and stage of development. The larvae eat plant and animal microorganisms. As they grow older, the need for live food appears. These are already real predators, feeding on worms, insects and small vertebrates. During the heat, their appetite increases. The inhabitants of the tropics are much more voracious than their relatives from countries with a temperate climate.
Amphibians at the beginning of life, whose photos adorn atlases, clearly showing the evolution of human development, develop rapidly, but over time their growth slows down greatly. The growth of frogs continues up to 10 years, although they reach maturity by 4-5 years. In other species, growth stops only by the age of 30.
In general, it should be noted that amphibians are very hardy animals that can endure hunger as well as reptiles. For example, a toad planted in a damp place can go without food for up to two years. The respiratory system of amphibianscontinues to function fully.
Amphibians also have the ability to regenerate lost body parts. However, in highly organized amphibians, such properties are less pronounced or absent altogether.
Like reptiles, amphibians also heal quickly. Tailed species are distinguished by special survivability. If a salamander or a newt is frozen in water, then they fall into a stupor and become brittle. As soon as the ice melts, the animals come back to life. It is necessary to remove the newt from the water, it instantly shrinks and does not show signs of life. Put it back and the newt immediately comes to life.
The body shape and skeletal structure are similar to fish. The brain consists of two hemispheres, the cerebellum and the midbrain, and has a simple structure. The spinal cord is more developed than the brain. The teeth of amphibians serve only to capture and hold prey, but are not at all adapted for chewing it. The respiratory and circulatory systems are of great importance for the life of amphibians. They have cold blood like reptiles.
In appearance and lifestyle, amphibians (turtles, we recall, do not belong to them, although sometimes they lead a similar lifestyle) are divided into three groups: tailless, tailed and legless. Anurans include frogs, which are distributed throughout the world, where there is moisture and enough food. Frogs love to sit on the shore and bask in the sun. At the slightest danger, they rush into the water and burrow into the mud.
Representatives of such a huge group of animals as the class Amphibians are good swimmers. With the approach of cold weather, amphibians fall intohibernation. Spawning occurs in the warm season. The development of eggs and tadpoles is fast. Their main food is plant and animal food.
Tailed amphibians look like lizards. They live in water bodies or near water. They are nocturnal and hide in shelters during the day. Unlike lizards, they are clumsy and slow on land, but very agile in water. They feed on small fish, mollusks, insects and other small animals. This species includes salamanders, newts, proteas, cryptogills, etc.
The order of legless amphibians includes caecilians, which look like snakes and legless lizards. However, in development and internal structure, they are close to salamanders and proteas. Worms live in tropical countries (except Madagascar and Australia). They live underground, making passages. They lead the same way of life as the earthworms that make up their diet. Some worms bring viviparous offspring. Others lay their eggs in soil near or in water.
Benefits of amphibians
Amphibians are among the first and most primitive inhabitants of the land, occupying a special place in the evolution of terrestrial vertebrates, which is the least understood.
For example, the role of birds and mammals in human life has long been known. In this regard, amphibians are very far behind. However, they are also of great importance in human economic activity. As you know, in many countries, frog legs are considered delicacies and are highly valued. For these purposes inEurope and North America annually harvested about a hundred million frogs. This indicates that amphibians are also of economic importance.
Adults feed on animal food. Eating harmful insects in gardens, orchards and fields, they benefit humans. Among insects, mollusks or worms, there are also carriers of dangerous various diseases.
Amphibians that feed on aquatic microorganisms are considered less useful. Tritons are an exception. And although their food is based on aquatic organisms, they also eat mosquito larvae (including malaria), which breed in reservoirs with warm and stagnant water.
The benefits of amphibians largely depend on their number, seasonal, food and other characteristics. All these factors affect the nutrition of amphibians. For example, a lake frog that lives in water bodies is more useful than its relatives living in other places.
Unlike birds, amphibians exterminate a larger number of insects that have deterrent and protective functions that birds do not eat. Also, land species of amphibians feed mainly at night, when many insectivorous birds sleep.
The full significance of amphibians in human life can only be appreciated with sufficient study of these animals. At present, amphibian biology has an extremely superficial knowledge.
Amphibians as an important part of the food chain
For some fur-bearing animals, most amphibians are the main food. For example, the survival rate of a raccoon dog in different habitats directly depends on the numberamphibians in these areas.
Mink, otter, badger and black polecat eat amphibians willingly. Therefore, the number of these animals is significant for hunting grounds. Amphibians are also included in the diet of other predators. Especially when there is not enough basic food - small rodents.
In addition, valuable commercial fish feed on frogs in ponds and rivers in winter. Most often, their prey is the common frog, which, unlike the green frog, does not burrow into the silt for wintering. In summer, it eats terrestrial invertebrates, and in winter it goes to winter in the lake. Thus, the amphibian becomes an intermediate link and replenishes the food supply for fish.
Amphibians and science
Due to their structure and survivability, amphibians began to be used as laboratory animals. It is on the frog that the largest number of experiments are carried out, ranging from biology lessons at school to major medical research by scientists. For these purposes, more than tens of thousands of frogs are used annually as biological material in laboratories. It is possible that this can lead to the complete extermination of animals. By the way, catching frogs is prohibited in England, and they are now under protection.
It is difficult to enumerate all the scientific discoveries related to experiments and physiological experiments on frogs. Recently, their use has been found in laboratory and clinical practice for the early diagnosis of pregnancy. The introduction of the urine of pregnant women into male frogs and toads causes a rapid process in them.spermatogenesis. In this regard, the green toad stands out in particular.
The most unusual amphibious planets
Among the little-studied species of these animals, there are many rare and unusual specimens.
For example, ghost frogs (genus Heleophryne) are actually the only family of anurans with only six species, one of which is found only in the cemetery. Apparently, this is where such a rather unusual name of the species came from. They live mainly in the northeast of South Africa near forest streams. They have sizes up to 5 cm and camouflage color. They are nocturnal and hide under rocks at night. True, today two species are almost exterminated.
Proteus (Proteus anguinus) is a tailed species of the class Amphibians living in underground lakes. Reaches a length of up to 30 cm. All individuals are blind and have transparent skin. Proteas hunt thanks to the electrical sensitivity of the skin and the sense of smell. They can live without food for up to 10 years.
The next representative, Gardner's zooglossus frog (Sooglossus gardineri) belongs to one of the unusual tailless species of the Amphibian family. It is under threat of destruction. It has a length of no more than 11 mm.
Darwin's frog is a fairly small tailless amphibian that lives in cold mountain lakes. Body length about 3 cm. Males carry their offspring in a throat pouch.
Interesting facts about amphibians
- Even not all avid travelers know that in the state of Peru there are many cafes where they cookspecial frog cocktails. It is believed that such drinks relieve many diseases, treat asthma and bronchitis, and help restore potency. One way to prepare it is to grind a live frog in a blender with the addition of bean soup, honey, aloe juice and poppy root. Are you ready to dare and try this dish?
- Unusual amphibians live in South America. Paradoxical frogs decrease in size as they grow older. The usual length of an adult is only 6 cm. However, their tadpoles grow up to 25 cm. A strange feature.
- During experiments on laboratory frogs, Australian researchers made an accidental discovery. They found that these animals are able to remove foreign bodies from their body through the bladder. Experienced and very eminent scientists implanted transmitters in animals, which after a while moved into their bladders. Thus, it turned out that when foreign objects enter the body of amphibians, they gradually become overgrown with soft tissues and are drawn into the bladder. This discovery actually revolutionized the scientific field.
- Few ordinary people know that the reason for the frequent blinking of frogs while eating is pushing food down the throat. Animals are not able to chew food and push it with their tongue into the esophagus. By blinking, the eyes are pulled into the skull by special muscles and help push food through.
- A very interesting specimen is the African frog Trichobatrachus robustus, which has an amazing adaptation forprotection from enemies. At the moment of threat, her paws pierce the subcutaneous bones, forming a kind of "claws". After the danger has passed, the "claws" retract and the damaged tissue regenerates. Agree, not every representative of modern fauna can boast of having such a useful and unique feature.
