It seems to almost all of us that without any special problems we can define any concept from the program of a comprehensive school. For example, amphibians are frogs, turtles, crocodiles and similar flora representatives. Yes, this is correct. We are able to name some representatives, but what about the description of their characteristic features or lifestyle? For some reason, they were allocated to a special class? What is the reason? And what is the pattern? This, you see, is more complicated.
What will they surprise us with?
It is likely that the respiratory system of amphibians is different from a similar internal structure, say, of mammals or reptiles. But what? Are there any 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 not only learns about what amphibians are similar to each other (turtles and crocodiles, by the way, do not belong to them), but also get acquainted with the most interesting facts related to the data animals. We guarantee that you didn’t even know something. Why? The thing is that a paragraph of a school textbook does not always provide the entire necessary range of knowledge.
General class information
The Amphibian (or Amphibian) class represents primitive vertebrate animals whose ancestors changed their habitat more than 360 million years ago and emerged from land to land. Translated from the ancient Greek language, 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 external living conditions.
In the warm season, they are usually active, but when cold weather sets in, they hibernate. Amphibians (frogs, newts, salamanders) appear in water, but spend the bulk of their existence on land. This feature can be called almost basic in the life of this species of living creatures.
Amphibian species
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 not more than one meter. The exception is the giant salamander (the main signs of amphibians in it are seemingly smeared), living in Japan and reaching a length of one and a half meters.
Amphibians spend their lives alone. Scientists have determined 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 perfectly masked, changing their color. By the way, not everyone knows that poison, secreted by special skin glands, also serves as protection against predators. Perhaps this feature is possessed only by reptiles, arthropods and amphibians. Mammals with such a set of characteristic features do not occur in nature. In fact, it’s even hard to imagine how, for example, a cat familiar to all of us could adjust the temperature of its own body depending on changes in the environment or emit poison, defending itself against a dog attacking it.
Features of the skin
All amphibians have a smooth thin skin, rich in skin glands, which secrete mucus necessary for gas exchange.
Excreted mucus also protects the skin from drying out and may contain toxic or signaling substances. The multilayer epidermis is abundantly equipped with a network of capillaries. Most poisonous individuals can take a bright color, which serves as a protective and warning device from predators.
In some amphibians of the tailless group, keratinous formations are found on the upper layer of the epidermis. This is especially developed in toads, in which more than half of the skin surface is covered with a stratum corneum. It is important to note that weak keratinization of the cover does not prevent the penetration of water through the skin. Thus, the breathing of amphibians is arranged, which are able to breathe under water only with the skin.
In terrestrial species, keratinized skin can form claws on the limbs. In tailless amphibians, the entire subcutaneous space is occupied by lymphatic gaps - cavities where a store of water accumulates. And only in a few places does the connective tissue of the skin connect to the amphibian muscles.
Amphibian lifestyle
Amphibians, photos of which can be found in all zoology textbooks, undergo several stages of development: those born in water and resembling fish as a result of transformation acquire pulmonary breathing and the ability to live on land.
Such development does not occur 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. In others, adults live on land, but in places with high humidity and near water.
During a drought, amphibians (birds could envy such a feature) fall into suspended animation, burrowing into the sludge, and are subject to hibernation in cold climates.
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 water-land inhabitants who usually prefer a nocturnal lifestyle. The day is spent in shelter or half asleep. Tailed species move on the ground like reptiles, and tailless species - in short jumps.
Amphibians are animals that are usually able to climb trees. Unlike reptiles, adult males of amphibians are very vociferous, in youth they are silent.
Nutrition in most cases depends on age and stage of development. Larvae eat plant and animal microorganisms. As you grow older, there is a need for live food. These are real predators that feed on worms, insects and small vertebrates. During the heat, their appetite rises. The inhabitants of the tropics are much more voracious than their relatives from temperate countries.
At the beginning of life, amphibians, whose photos are decorated with atlases that clearly show the evolution of human development, are developing rapidly, but over time their growth is greatly slowed down. The growth of frogs lasts up to 10 years, although they reach maturity by 4-5 years. In other species, growth ceases only by the age of 30.
In general, it should be noted that amphibians are very hardy animals that can tolerate hunger no worse than reptiles. For example, a toad planted in a damp place can be without food for up to two years. The respiratory system of amphibians continues to function fully.
Amphibians also have the ability to regenerate lost parts of the body. However, in highly organized amphibians, such properties are less pronounced or even absent.
Like reptiles, amphibians also quickly heal wounds. Tail species are particularly survivable. If the salamander or newt is frozen in water, then they become numb and brittle. As soon as the ice melts, the animals come back to life again. Once a newt is taken out of the water, it instantly shrinks and shows no signs of life. Put it back - and the newt immediately comes to life.
The body shape and skeleton structure are similar to fish. The brain consists of two hemispheres, cerebellum and midbrain and has a simple structure. The spinal cord is more developed than the brain. Amphibian teeth serve only to capture and hold prey, but are not at all adapted to chew it. The respiratory and circulatory systems are of great importance for the life of amphibians. They, like reptiles, have cold blood.
In appearance and way of life, amphibians (turtles, recall, do not belong to them, although they sometimes lead a similar lifestyle) are divided into three groups: tailless, tailed and legless. To the representatives of tailless include frogs, which are spread around the world, where there is humidity and enough food. Frogs like to sit on the beach and bask in the sun. At the slightest danger, they rush into the water and burrow into the sludge.
Representatives of such a huge group of animals, like the Amphibian class, swim well. With the approach of cold weather, amphibians hibernate. 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 lead a nocturnal lifestyle, and during the day they hide in shelters. Unlike lizards, on land they are slow and slow, but very agile in water. They feed on small fish, shellfish, insects and other small animals. This species includes salamanders, newts, protea, tamaris, etc.
Worms that resemble snakes and legless lizards belong to the order of legless amphibians . However, in terms of development and internal structure, they are close to salamanders and proteins. Worms live in tropical countries (except Madagascar and Australia). They live underground, making moves. They lead the same lifestyle as earthworms that make up their diet. Some worms bring viviparous offspring. Others lay eggs in the soil next to or in the water.
The 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 studied.
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 delicacies and are highly valued. For these purposes, about one hundred million frogs are caught annually in Europe and North America. This suggests that amphibians are also of economic importance.
Adults eat animal food. Eating harmful insects in gardens, gardens and fields, they benefit the person. Among insects, mollusks or worms, carriers of various dangerous diseases are also found.
Amphibians that feed on aquatic microorganisms are considered less useful. The exception is tritons. And although aquatic organisms are the basis of their food, they also eat mosquito larvae (including malarial ones), which breed in bodies of water with warm and stagnant water.
The benefits of amphibians are largely dependent 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 greater number of insects with repelling and protective functions that birds do not eat. Also, terrestrial amphibian species feed mainly at night, when many insectivorous birds sleep.
The full significance of amphibians in human life can be assessed only with sufficient study of these animals. Currently, the biology of amphibians has an extremely superficial knowledge.
Amphibians as an important part of the food chain
In some fur animals, most amphibians are the main food. For example, the survival rate of a raccoon dog in different habitats directly depends on the number of amphibians in these areas.
Mink, otter, badger and black polecat willingly eat amphibians. Therefore, the number of these animals is significant for hunting grounds. Amphibians are included in the diet of other predators. Especially when there is not enough basic food - small rodents.
In addition, valuable commercial fish in winter in ponds and rivers feed on frogs. Most often, the grass frog becomes their prey, which, unlike the green frog, does not bury itself in silt for wintering. In summer, it eats terrestrial invertebrates, and in winter goes for wintering in the lake. Thus, the amphibian becomes an intermediate link and replenishes the forage base for fish.
Amphibians and science
Due to their structure and vitality, 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 classes at school to large 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, in England, fishing frogs is prohibited, and they are now under protection.
It is difficult to list all the scientific discoveries associated with experiments and physiological experiments on frogs. Recently, they have been found to be used in laboratory practice for the early diagnosis of pregnancy. The introduction of the urine of pregnant women to male frogs and toads causes them to rapidly spermatogenesis. In this regard, the green toad stands out especially.
The most unusual amphibians of the planet
Among the poorly studied species of these animals, there are many rare and unusual specimens.
For example, ghost frogs (the genus Heleophryne) are actually the only family of tailless amphibians with only six species, one of which is found only in the cemetery. Apparently, this is where the rather unusual name of the species came from. They live mainly in the north-east of South Africa near forest streams. They are up to 5 cm in size and camouflage. They lead a nocturnal lifestyle, and at night hide under stones. True, today two species are almost exterminated.
Proteus (Proteus anguinus) is a tailed species of the Amphibian class, living in underground lakes. Reaches lengths up to 30 cm. All individuals are blind and have transparent skin. Proteus are hunted due to the skin's electrical sensitivity and sense of smell. They can live without food for up to 10 years.
The next representative, the frog zooglossus Gardner (Sooglossus gardineri) belongs to one of the unusual tailless species of the Amphibian family. Endangered. It has a length of not more than 11 mm.
Darwin's frog is a rather small tailless species of amphibians that lives in cold mountain lakes. Body length about 3 cm. Males carry their offspring in a throat sac.
Interesting facts about amphibians
- Even not all avid travelers know that in the state of Peru there are many cafes where they prepare special frog cocktails. It is believed that such drinks relieve many diseases, treat asthma and bronchitis, and help restore potency. One way to cook is to grind a living frog in a blender with the addition of bean stew, honey, aloe juice and poppy root. Are you ready to decide 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 reaches only 6 cm. However, their tadpoles grow to 25 cm. A strange feature.
- During experiments on laboratory frogs, Australian researchers made a random discovery. They found that these animals were able to remove foreign bodies from their bodies through the bladder. Experienced and very eminent scientists implanted transmitters into animals, which after some time moved into their bladders. Thus, it turned out that when amphibians enter the body, foreign objects gradually grow into soft tissues and are drawn into the bubble. 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 into their throats. Animals are not able to chew food and push it with the tongue into the esophagus. Blinking, the eyes are drawn into the skull with special muscles and help push food through.
- A very interesting specimen is the African frog Trichobatrachus robustus, which has an amazing device for protection against enemies. At the time of threat, her paws pierce the subcutaneous bones, forming a kind of “claws”. After the danger has passed, the "claws" are pulled back, and the damaged tissue regenerates. You must admit that not every representative of the modern fauna can boast of the presence of such a useful and unique feature.