Did You Know?
The largest living species of amphibian is Chinese Giant Salamander (Andrias davidianus) -- 1.8 meters long; whereas the smallest amphibian is microhylid frog (Paedophryne amauensis) with an average length of 7.7 mm.
Amphibians are vertebrate animals residing in a wide range of habitats, such as aquatic, terrestrial, and arboreal. Evolution of the earliest amphibians took place in the Devonian period; their features modified over a period of time. While some are extinct, following are the characteristics of the extant species of class Amphibia.
The color of the skin of amphibians is a result of three layers of cells called chromatophores.
- Deepest layer is made up of melanophores.
- Intermediate layer consists of guanophores giving the organism the blue-green color.
- Topmost layer consists of lipophores, which give the yellow color to the organisms.
Skin of the amphibians is capable of exchanging gas, which helps fully-grown amphibians to respire underwater, and also helps them during their state of hibernation (resting state or dormancy).
The skeleton of amphibians is similar to that of tetrapods or vertebrates having four legs. Most of the amphibians have hollow ossified bones and an overall lightweight skeletal system.
Amphibians are poikilothermic, that is, their body temperature varies with the environment.
Most of the water that an amphibian needs is soaked in through their permeable skin; thus, they rarely drink water.
Amphibians have a three-chambered heart with a rather complex blood vessel system forming a double-loop circulation.
Amphibians (especially frogs) have a peculiar characteristic of developing lungs in place of gills once they mature.
hese organisms also possess green rods in their retinas, which help them differentiate different colors. Double-channel hearing arrangement and two-part teeth are also characteristics of amphibians.
Frogs and Toads (Order - Anura)
Anura has a Latin-Greek origin -- an means without and oura means tail.
Not always, but usually, organisms having a smooth skin are called frogs, whereas those with warty skin are known as toads.
In frogs, the glands that produce poison are situated on the backs of frogs and behind the ears of toads.
Frogs have long limbs -- the forelegs being shorter than the hind legs -- and webbed toes.
The shape of the legs and feet varies based on the habitat of the frog, whether it is water-dwelling, tree-dwelling, or living in burrows.
Fully-grown or adult frogs neither have tails nor do they have the ability to regrow limbs.
Frogs do not have an external ear; they have their eardrum on the head behind their eyes.
The operculum-columella complex (two bones in the middle ear transmitting sound to the inner ear) helps in channelizing both airborne and seismic signals.
Extreme climatic conditions compel frogs into a state of aestivation (similar to hibernation, typically related to warm climatic conditions); during this time, they respire through their skin.
Certain species of frogs, for example Namaqua Rain Frog and Malagasy Rainbow Frog, are reported to inflate themselves in front of a predator. European spadefoot toad is also known to inflate itself for self-defense.
The tailed frogs prefer habitat with cold water, whereas tree frogs are known to grow on plants, trees, and under the leaves.
Widely regarded as the most poisonous frog, the golden poison frog is endemic to Columbia.
Most of the frogs undergo external fertilization and reach the "tadpole stage" inside the eggs; hence they take birth in the form of smaller version of the adult frogs.
Salamanders (Order - Caudata)
Caudata is a Latin word for tail and the order comprises elongated animals resembling a lizard called salamanders.
Salamanders do not possess claws and sport a smooth or tuberculate skin with no scales.
Poison-producing glands in salamanders are situated behind their eyes.
Salamanders may choose a terrestrial or an aquatic habitat. Newts are similar to salamanders, but they live their entire life in water.
In most of the salamander species, the limbs are developed at a right angle to the body having almost the same length.
Along with bright colors, tails are the most prominently used method of self-defense against their predators. A salamander distracts a predator by losing or detaching its tail from the body; the tail wriggles for a while. During this time, the salamander either runs away or stays still, that is, it "plays dead."
Salamanders without lungs (around 350 in total) possibly communicate with their nose.
Both newts and salamanders can be found in rivers and streams.
Most species of salamanders undergo internal fertilization. Like frogs, even in salamanders, the larvae form tadpoles within the eggs.
Caecilians (Order - Gymnophiona)
These are worm-like animals without any limbs often found residing underground.
The body is covered with folded skin containing scales. The skin also covers their eyes limiting their vision.
They have a pair of tentacles between their nostrils and eyes.
Caecilians feed on larvae of beetles, small lizards, and termites.
These are the only members of the class Amphibia which reproduce internally, exclusively.
Due to varied reasons, prominently urbanization, these animals today suffer from loss of habitat. Thus, species, such as golden poison frog are now threatened. On a personal level, you can stop the situation from getting worse by spreading awareness.