What are amphibians?
Amphibians are vertebrates that scientists believe evolved from a fish known as a coelacanth. The group includes toads, frogs, salamanders and caecilians. Caecilians resemble snakes and are almost entirely subterranean. Amphibians are important in the ecosystem, but are also sensitive to man-made changes.
Salamander larvae hunt and feed on small animals in the water, while frog and toad larvae mainly feed on plants and dead animals. Adult salamanders, frogs and toads feed on insects, spiders, snails, worms and other small animals. The amphibians help keeping the number of insects and other small insects down. This reduces the spread of diseases such as malaria, and there will be fewer pests on crops. The presence of amphibians in an ecosystem is a good sign of high biodiversity.
The lungfish is a member of the group lobe-finned fishes, the group believed evolved into land-living amphibians a long time ago.
The Amazon milk frog lives in the Amazon rainforest, and belongs to the group amphibians.
Photo: Ellika-Nordström-Malmö-Museums
Toads are also amphibians, like this European green toad.
Photo: Frank-Vassen-CC-BY
Salamanders are also amphibians, like this Luristan newt.
Photo: Ellika-Nordström-Malmö-Museums
Caecilians are the un-knowns of the amphibian group. They look like large earthworms or strange snakes, and live mostly in the tropics. The photo shows a caecilian guarding its eggs.
Photo: Davidvraju-CC-BY-SA
Undergoes metamorphosis
There are about 7,500 different species of amphibians in total. Amphibians are ectothermic, which means that their body temperature adapts to their environment. Species that live where it gets too cold for part of the year go into hibernation.
Most amphibians go through metamorphosis, a change in body shape. It starts with the female laying eggs that hatch into a larva. The larva lives entirely in water and breathes with gills. It then undergoes a multi-step transformation into an adult that breathes through its skin and with its lungs. The skin is covered by a protective layer of mucus.
The amphibians are an important part of the ecosystem, both because they eat insects and other small invertebrates, and because they themselves are food for many birds and other animals.
Photo: Pierre-Dalous-CC-BY-SA
Eggs from the red-eyed treefrog.
Photo: Geoff-Gallice-CC-BY
The red-eyed tree frog goes through metamorphosis, from egg and tadpole to fully grown frog. This tadpole has gotten its legs but not yet shed its tail.
Photo: Ellika-Nordström-Malmö-Museums
The metamorphosis from tadpole to small toad in the common toad species.
Photo: Cwmhiraeth-CC-BY-SA
Close-up on a tadpole.
Photo: LiquidGhoul-CC-BY-SA
A salamander larvae that has not yet lost its gills.
Photo: Piet-Spaans-CC-BY-SA
Amphibians have an amazing ability to regrow lost body parts. This salamander has a lost tail that is growing back.
Photo: Greg-Schechter-CC-BY
The Asiatic toad is one of the amphibian species that has become interesting in medical research, because it secretes substances that can help against many diseases.
Photo: Fedorova-Nadezhda-CC-BY
Medicines thanks to amphibians
By looking at how different animals, plants and fungi solve problems, we humans have been able to mimic nature. Humans have been able to make many medicines because we have studied different species of frog. Painkillers, medicines for cancer, stomach ulcers and viral infections are just a few examples of the help we have received from frogs. Amphibians also have an amazing ability to replace lost body parts or tissue. Hopefully, this can help us humans understand how we could better help patients with lost cells, or maybe even organs.