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Who are amphibians?
The smallest class of vertebrates, Amphibians, has approximately 4,500 species in the world. On these WWW pages we are dealing with amphibians living in Estonia, that belong to two orders: (Caudata) and tailless amphibians (Anura). You can read about them in Estonian Amphibians.
How do amphibians look like?
Caudata have a lizard-like body, tailless amphibians (frogs) have a short, broad body. Most adult amphibians have two pairs of legs that they use for moving in various degrees. Tadpoles, that live in the water, have no limbs at first. The skin of amphibians is thin and naked but contains a great number of glands. The skin of the species that live in the water is covered with mucous. The amphibians that live in tropical areas are often very colorful but our widespread species have inconspicuous protective color. The largest amphibian is the Chinese giant salamander weighing up to 65 kg. The largest known frog is the rare African goliath frog that can be 87 cm long with legs extended and weigh up to 3.7 kg. The smallest amphibian is a frog that is only 1.2 cm long. It lives in Cuba.
Where do amphibians live?
The word amphibian (in Estonian kahepaikne) means "double life". Thus as the name suggests amphibians live in two worlds - water and dry land. Some of them spend most time in the water, the others go into water for the time of reproduction. Majority of amphibian species can be found in temperate and tropical zones. However, some of frogs are adapted to arid environments, including deserts. Estonian species live near the bodies of water. In order to survive unfavorable weather conditions (winters), they bury themselves in mud in the body of water and come out only in warmer weather in spring.
How do amphibians move?
Due to weak legs Caudata move like snakes. Tailless amphibians either leap thanks to their powerful back legs (e.g. grass frog) or walk (e.g. ordinary toads). Great majority of amphibians can swim in water.
How do amphibians breathe?
Amphibians breathe through lungs but doing it through skin is important as well - that is the reason why their skin has to be damp all the time. Some species of salamanders do not have lungs at all. Likewise tadpoles developing in water breathe through gills.
What is the circulatory system of amphibians like?
A three-chambered heart pumps blood into the pulmonary and systemic circulation. As there is no complete separation between the two circulations, the metabolism of amphibians is slow and they are cold-blooded.
What do amphibians eat?
Amphibians are generally carnivorous. They eat smaller invertebrates than they themselves are: insects, worms, and other animals small enough to be swallowed whole. Large tailless amphibians can swallow small vertebrates.
What are the main organs of senses of amphibians?
Vision is quite well developed among the most species of amphibians. The eyes of amphibians in contrast to fishes have eyelids and lachrymal glands. The organs of hearing are behind the eyes. The organs of smell are connected with nostrils that open further than eyes.
How do amphibians reproduce and develop?
Majority of amphibians are bisexual. Even the species that live on dry land return to the bodies of water to reproduce. However, some of them spawn in foam-nests. Similarly to fishes the most species of amphibians have extra-corporal fertilization - it takes place in the water during the spawning time. The most , but not all the amphibians go through a metamorphosis, as they develop into adults. Usually, the fertilized egg becomes a tadpole. At first the tadpole breathes through gills and feeds on plants. During some months it gradually develops limbs and becomes similar to adults of the particular species.