Amphibian Facts

The word 'amphibian' is derived from the Greek word 'amphibios', which means a double life. The amphibians include the animals that live in the water as well as on the land. They start their life underwater and move on the land in their adulthood. There are more than 6,000 existing species of amphibians. There are three types of amphibians such as toads, frogs and salamanders. Salamanders including mud puppies and newts belong to the order Caudata. Frogs and toads belong to the order Anura and caecilians are included in the order Apoda.

Habitat of Amphibians

Amphibians live in various environment. However, most species of amphibians require freshwater habitats such as swamps, ponds, streams or wet environment for breeding. Some of the frog species rely on the pools of water that is collected in the cup-shaped bases of plants or tree hollows.

Physical Characteristics of Amphibians

Amphibians are cold-blooded, vertebrate animals. Their body temperature changes according to the temperature changes of the surroundings. Their size is variable, ranging from 1.5 m long Japanese giant salamander to small frogs such as 1 cm long gold frog. Most frogs measure between 2-8 cm, while most salamanders are 5-20 cm in length. Most species of caecilians are 10-50 cm in size. They have a soft, smooth skin, covered with moist slime, mucus. Their skin is permeable and allows the gases and liquids to pass through it. It is a peculiar characteristic of the amphibians. In many species of amphibians, mucus-secreting glands in the skin are modified to produce the toxins that repel the predators. They have a sticky tongue to catch the food.

Most adult amphibians possess teeth. However, in some species, teeth are reduced or totally absent. Teeth are used to hold the prey, not for chewing. Most amphibians start their lives as a larva, which has a remarkably different body from the adult. Amphibian larva has a number of features similar to the fish. These larvae are called tadpoles or pollywogs and they live in the water. They possess gills at the sides of the head, with which they can breathe underwater. They also have a tail, used for swimming.

Amphibians come in a wide variety of colors. Some of the amphibians are brilliantly hued, while some display the drab coloring, mixing with their muddy habitat. Amphibians have a diverse coloration to the pigment granules in the upper layer of the skin and specialized pigment-containing cells, chromatophores, in the lower levels of the skin. Many amphibians can change their skin color by dispersing or concentrating different pigments in the chromatophores. It helps them adjust their body temperature as light colors reflect more heat than dark colors. A color change of the skin acts as a camouflaging mechanism and helps them escape from the predators.

Caecilians are the only amphibians that are blind. Their eyes are covered with the skin or bone. They have two small tentacles at both sides of the head, which are used to detect the chemical changes in the environment.

Nutrition of Amphibians

Almost all adult amphibians are carnivorous and feed on a wide variety of prey such as spiders, worms, insects, crustaceans, small reptiles and even small amphibians. Salamander feeds by sucking its prey into its mouth. When on land, it flicks out its sticky tongue to capture a small prey. Caecilians approach their prey slowly and kill it quickly with their sharp teeth. Frog captures its prey using its tongue, which is attached at the front of its mouth.

Reproduction of Amphibians

Most amphibians need a freshwater environment for breeding. The eggs of the amphibians are surrounded by a protective, clear, jellylike substance. The eggs are placed in the water or in a damp place, so that the developing embryo would not dry out. Most amphibians lay their eggs inside the water. However, some of the frogs, salamanders and all caecilians lay their eggs in moist places such as cracks or burrows in the ground, or leaf litter. A development of juvenile, water-breathing form to adult, air-breathing form occurs through a process known as metamorphosis. During the process of metamorphosis, there is a formation of four legs. The gills are replaced by the lungs as respiratory organs. The skin develops certain glands to avoid dehydration. An eardrum is developed, so that the middle ear is locked. In toads and frogs, the tail disappears.