The meaning and diversity of amphibians in nature

The diversity of amphibians, their significance in nature and for humans, the characteristics of these animals - you will learn about all this after reading the article. Amphibians are otherwise called amphibians. They originated from fish-like ancestors in the Upper Devonian, about 350 million years ago. At that time, extensive swamps, overgrown with ferns along the coast, were deserted and represented ideal habitats for their development by the first terrestrial animals, who did not yet know how to retain moisture in the body.

The first amphibians

It did not immediately appear all the modern diversity of amphibians. Photo of ancient animals, unfortunately, no. Surely they looked very impressive. Paleontological material shows that the first amphibians resembled giant salamanders with an oblong head and a well developed tail. These animals, reaching more than 1 m in length, moved slowly and awkwardly, with difficulty creeping from one reservoir to another. In the Carboniferous there is already a rather large variety of amphibians. But they all led a sedentary lifestyle, almost without experiencing any competition from other animals, since there was plenty of food.

Difficulties of adaptation

The present diversity and importance of amphibians have evolved in the course of a long evolution. The transition from water to terrestrial existence created many problems for these animals. Amphibians needed millions of years to develop the necessary adaptations. In fact, the diversity of amphibians is characterized by the fact that these animals have not been able to fully adapt to the harsher conditions of terrestrial habitation and still need an aquatic environment for reproduction. For better movement, the amphibians developed a light skeleton and powerful muscles to overcome gravity. The extremities of the first amphibians were short, massive and widely spaced, though already five-fingered. For breathing amphibians used paired air bags, or lungs.

Modern amphibians

Of the many groups of amphibians that once existed, only three detachments remained: Anura (frogs and toads), Urodela (Tritons and Newts) and Apoda (worms - elongated blind burrowing forms). Frogs and toads are over 2500 species. The variety of amphibians belonging to Anura has adapted to life not only near water bodies, but also in tropical forests, steppes and even deserts.

Characteristics of frogs and toads

A common feature of all frogs and toads is development with complete transformation (metamorphosis). They all have a voice device, but it only reaches full development in males, who make cries, attracting females during the mating season or in fright. Typical croaking sounds are obtained due to fluctuations in the vocal cords - paired folds of the laryngeal mucosa. Air passes them into the lungs when inhaled and back from the lungs into the vocal bags located under the oral cavity. Almost all the frogs and toads of the temperate zone in spring are sent to the water. They choose the right direction, guided by special susceptible cells - osmoreceptors located in the oral cavity. For unknown reasons, only a few ponds are attractive for amphibians, and in them a great number of frogs and toads gather during the breeding season. Males usually come first and call females by marriage cries.

Skin amphibians

In the larval stages, frogs, toads, newts and salamanders breathe in the water by the outer gills that disappear during metamorphosis. Adult frogs can breathe in three ways. With a high level of activity, they carry out this process by the lungs and mouth, and during hibernation - by the surface of the skin. In the air, skin moisture is maintained through the secretion of mucus glands. In the skin are also poisonous glands, especially well developed in tropical frogs of the genera Dendrobates and Phyllobates. Their potent poison, the South American Indians greased arrows, with which they hunted birds and monkeys.

Many poisonous amphibians are brightly colored, which serves as a warning for predators. Widespread in amphibians and camouflage coloring. Skin pigment cells (3 types), thickening or dispersing the pigment, cause discoloration.

Tritons and salamanders

Tritons and salamanders (one of which is presented in the photo above) deviated less from the original type of amphibian structure. According to the shape of the body, the tailed amphibians resemble lizards. They have a clearly marked head. Adult animals and larvae are very similar to each other, and complete metamorphosis, characteristic of frogs and toads, does not occur in tailed amphibians. There are 8 families of caudate with about 225 species. Like frogs and toads, they usually breed in water. Fertilization in these animals is internal. The male excretes the spermatophore, which the female captures with cloaca. Most tailed lay eggs.

Marriage behavior of newts and salamander

During breeding, the males of newts acquire a vivid color, which plays an important role in their vigorous marital courtship. For some salamanders, neoteny is characteristic - when ripe individuals retain the typical features of the larval organization: external gills, transparent slightly pigmented skin, etc. As a result of pedogenesis, the animal becomes sexually mature at the larval stage. An example of this kind is the axolotl shown in the photo above (larva Ambystoma mexicanum).

Chervyagi

Worms are the smallest and least studied group of amphibians. Many of them lead a burrowing lifestyle. There are no limbs in these animals. An interesting primitive sign of worms is the preservation of scales in the skin. Eyes are strongly reduced, and their function is partly replaced by special tactile tentacles, by which animals correct their movement under the ground. Ceylon fish fishes (Ichthyophis glutinosus), first described at the end of the 19th century, are better known than others. His photo is presented above.

The South American worm is a typical representative of legless amphibians. She is blind, lives underground and probably feeds on worms. This species is common only in subtropical and tropical regions. The South American worm hatchs its masonry. The animal reaches 50 cm in length.

So, we briefly described the diversity of amphibians. The role of amphibians in nature and human life is another interesting topic. We suggest you read about why these animals are so important.

The meaning of amphibians

In varying degrees for the human whole variety of amphibians is useful. Their importance is very great mainly because they feed on many kinds of harmful invertebrates (insects and their larvae, including mosquitoes, mollusks, etc.). These and other invertebrates damage forest and agricultural crops. In addition, they can be carriers of diseases of domestic animals or humans.

Continuing to describe the diversity and importance of amphibians, we note that food objects in terrestrial amphibians are usually more diverse than those that lead an aquatic life. For a day on average, a herbal frog eats 6 invertebrates, harmful to humans. If the number of these amphibians is 100 individuals per 1 hectare, they can destroy more than 100,000 pests during the summer activity. Often amphibians eat invertebrates that have an unpleasant taste or smell. Amphibians hunt at night and at dusk. Their useful activity, however, is generally small, since only in a few places do they reach a sufficient number. Tadpoles, caviar and adult specimens of amphibians, leading mainly to aquatic life, are the food for many commercial fish, herons, ducks, and other birds. Amphibians, in addition, constitute a significant part of the diet of a number of fur-bearing animals (horseradish, mink, etc.) in the summer. And otters eat frogs in winter.

In some regions (America, Southeast Asia, Italy, France), some people use amphibians (frogs, salamanders) for food. In the United States, for example, there are farms on which a bull-frog is bred (photo above). Only the hind legs go on sale, and the carcasses go to feed cattle. At one time, Ukraine also carried out fishing for green frogs. They were bred for export in the floodplains and estuaries of the Danube. However, their numbers quickly declined, and their production ceased.

In temperate latitudes the number of amphibians is small, so it is necessary to protect them. The diversity of amphibians and their protection is the guarantee of ecological balance.