Amphibians

Amphibians are a diverse and exciting class of animals that include frogs, toads, salamanders, newts and caecilians.

The term Amphibian comes from the Greek word amphibious. Amphi means “both” and bios means “life”. Those names refer to the two lives that many amphibians live – when they hatch from their eggs, amphibians have gills so they can breathe in the water. They also have fins to help them swim, just like fish. Later, their bodies change, growing legs and lungs enabling them to live on the land.

Amphibians are vertebrate animals (have a backbone) like fish, mammals, reptiles and birds and hundreds of millions of years ago, amphibians became the first vertebrates to live on land. They are cold-blooded, which means their body temperature is regulated by their surrounding temperature. Amphibians are also characterised by their smooth, slimy skin and their lack of scales, feathers or hair. Their skin is permeable (which means air can pass through the skin) and many amphibians therefore breathe through their skin instead of through their lungs.

There are three types of amphibians:

  1. Frogs – Generally, frogs have a short body, webbed fingers and toes, bulging eyes, and no tail. Frogs are good jumpers with long powerful legs. Toads are a type of frog. Two species of frogs are the American bullfrog and the poison dart frog.
  2. Salamanders - Salamanders look a bit like lizards. They have skinny bodies, short legs, and long tails. Salamanders can re-grow lost limbs and other body parts. They like wet, moist areas like wetlands. A newt is a type of salamander.
  3. Caecilians - Caecilians are amphibians that don't have legs or arms. They look a lot like snakes or worms. Some of them can be long and reach lengths of over 4 feet. They have a strong skull and a pointed nose to help them burrow through dirt and mud.

Top 10 facts

  1. Nearly all amphibians are capable of producing poisons from their skin. Some of these poisons are easily smelled.
  2. One way to tell a frog and a toad apart: frogs have smooth, clammy skin, while toads have drier, bumpy skin. Both frogs and toads lay their eggs in water, but toads spend more of their time on land than do frogs.
  3. More than 75 percent of all toad and frog species in the world live in tropical rainforests.
  4. Many frogs and salamanders take care of their young, either by guarding their eggs, carrying their young with them of by feeding tadpoles.
  5. Some frogs (such as wood frogs and Spring Peepers) are able to freeze solid during the winter and survive!
  6. All amphibians begin their life in water with gills and tails. As they grow, they develop lungs and legs for their life on land.
  7. There are more than 4,000 different kinds of amphibians. Members of this animal class are frogs, toads, salamanders, newts, and caecilians or blindworms.
  8. Frogs swallow their food whole. The size of what they can eat is determined by the size of their mouths and their stomach.
  9. Most amphibians hop or crawl to the safety of the nearest water when danger threatens. Some also have glands in their skin that ooze poisonous or foul-tasting fluids when they are attacked. The common toad and a few other species confuse predators by puffing themselves up to look bigger.
  10. Colour helps amphibians find mates and hide from predators and prey. Some species are brightly coloured to tell predators that they are poisonous. Others are camouflaged to blend in with their surroundings.

Did you know?

  • The most poisonous frog is the Golden Dart Frog, which has enough toxic secretions on its skin to kill up to 10 people. South American Indians use the skin secretions of poison dart frogs on the tips of their arrows to kill animals. The rough-skinned newt, common to Oregon in America, is very deadly. One college student several years ago swallowed one on a dare and he died because it gives off something known as a neurotoxin that paralysed his ability to breathe.
  • The largest amphibian is the Chinese Giant Salamander. It can grow to 6 feet long and weigh 140 pounds. The largest frog is the Goliath Frog which can grow to 15 inches long (not counting the legs) and weigh over 8 pounds. The smallest amphibian is a frog called the paedophryne amauensis. It is also the world's smallest vertebrate animal. It is about 0.3 inches long.
  • The best jumper is the South American Sharp-nosed Tree frog. It has been recorded to jump over 30 feet high – which is higher than a house!
  • A group of frogs can be called an army, chorus, or colony.
  • A group of toads can be called a knot or a nest.
  • A group of salamanders can be called a band.

Look through the gallery and see if you can spot the following:

  • The life cycle of a frog
  • Some common amphibians
  • A red-eyed tree frog
  • A salamander
  • A caecilian
  • A great-crested newt
  • A Goliath frog
  • Tadpole to frog

Gallery

About

The life cycle of Amphibians begins with an egg. A larva usually hatches from an egg (frog and toad larva are commonly referred to as tadpoles). The larva slowly develops into an adult by growing legs and arms and by developing lungs. The larval stage can last anywhere from 2 weeks to 2 years! Once the change is complete, the adult amphibian will emerge from the water and spend the majority of its life in the moist, surrounding habitat.

Not all amphibians go through the same metamorphosis process. Some frogs and salamanders, like the greenhouse frog and the red-backed salamander, lay their eggs on land. The larva develops inside the egg and the adult will hatch out of the egg on land. They will live their entire lives away from water. The marsupial frog puts her eggs in a pouch on her back. Within that pouch the larva develops into frogs. Once the larva has fully developed, it emerges from its protective pouch as a small frog.

Frogs and toads, also known as the tailless amphibians, live on every continent except Antarctica. Currently, there are more than 3,500 species of frogs worldwide. Because frogs are the only amphibians that can hear, they are also the only amphibians that have a voice box or larynx. During the summer, if there are frogs in the area you can often walk outside and hear frogs calling to establish their territory or to find a mate.

Salamanders usually have a long tail and four legs. Many people mistake salamanders for lizards and lizards for salamanders, but they are very different. Salamanders, unlike lizards, have smooth, slimy skin and a larva stage. Salamanders also do not have ears or a voice box. The 360 different species of salamanders worldwide are usually found in the cooler forested areas in the Northern Hemisphere.

Adult amphibians are carnivores and predators. They eat a variety of food including spiders, beetles, and worms. Some of them, like frogs, have long tongues with sticky ends that they flick out to catch their prey. The larvae of many amphibians mostly eat plants. Frogs have teeth, but toads do not. Most frogs have teeth on the upper jaw, yet they none on the lower jaw. Frogs' skin is slimy because they have protective skin secretions that ooze out of their bodies. Whereas frogs have smooth skin, toads' skin is rough and bumpy, due to special structures that secrete poisonous fluids from their skin.

Words to know:

Amphibian - a cold-blooded vertebrate that spends some time on land but must breed and develop into an adult in water
camouflaged - devices designed to conceal by imitating the colours of the surrounding environment
carnivores - an animal that eats other animals.
cold-blooded - describes an animal with an internal body temperature that varies according to the temperature of the surroundings
fins - a flexible organ, sometimes paddle-shaped or fan-shaped, extending from the body of a fish or other water animal and helping in balance and propulsion
gills - the organ that fish and some other water animals use to breathe, consisting of a membrane containing many blood vessels through which oxygen passes
glands - a cell or group of cells that secretes a specific substance
hatch - to emerge from an egg
larva - the immature, early-stage form of frogs and other animals that undergo marked changes during metamorphosis
metamorphosis - a complete or marked change in the form of an animal as it develops into an adult, e.g. the change from tadpole to frog or from caterpillar to butterfly
permeable - allowing liquids, gases, or magnetic fields to pass through
predators - a carnivorous animal that hunts, kills, and eats other animals in order to survive, or any other organism that behaves in a similar manner
prey - an animal or animals caught, killed, and eaten by another animal as food
regulated - to control something and bring it to the desired level
species - a kind, sort, or variety of something
toxic secretions – a poisonous substance discharged by a gland or organ
vertebrates - an animal with a segmented spinal column

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