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Amphibians: Traits, Types & Roles

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  • 0:02 Amphibian
  • 1:17 Traits
  • 1:56 Types
  • 4:18 Roles
  • 5:50 Lesson Summary
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Lesson Transcript
Instructor: Jayne Yenko

Jayne has taught health/nutrition and education at the college level and has a master's degree in education.

Amphibians. Does the word conjure up images of slimy frogs and salamanders? Or perhaps a case of warts after handling a toad? Amphibians are a fascinating group of animals that we don't see very often. Find out more in this lesson.

Amphibian

Can you imagine yourself down to the size of a tree frog, a bull frog, a salamander, or even a caecilian? How would the world look to you?

Amphibian means 'both kinds of life' in ancient Greek. It basically means animals that can live in both in water and on land. The smallest amphibian is the microhylid frog from New Guinea that was first discovered in 2012. It grows to about one third of an inch long, or 7.7 millimeters. The largest is the Chinese giant salamander at 5 feet 11 inches long, or 1.8 meters long. The African Goliath frog is the largest frog at 13 inches, or 32 centimeters, and 6.6 pounds, or 3 kilograms.

The class 'amphibians' includes Anura, which means 'without tails' and includes frogs and toads; Caudata, which means 'with tail' and is comprised of salamanders; and Gymnophiona, which means 'naked serpent' and is comprised of caecilians. There are about 7,000.

Traits

There are several characteristics all amphibians share:

  • Have a back bone and are considered vertebrates
  • Are cold-blooded, which means they are unable to regulate their own body temperature
  • Spend part of their lives in water and on land
  • Do not have scales but have permeable skin, which means that molecules and gases can pass through it
  • Have gills for at least part, or all, of their lives
  • Undergo metamorphosis, which means their bodies are transformed from their larval stage to their mature, adult stage

Types

There are three types of amphibians: the anura, or the frogs and toads; the caudate, or salamanders, and the gymnophiona, or caecilians. While all amphibians share some characteristics, each group has its own set of traits as well.

Anura is the group of frogs and toads. Their hind limbs are longer than their front ones. They have webbed toes but no claws, no tails, big eyes, and moist skin. We generally think of frogs as having smooth skin and toads having warts, but this is not always true. Toads tend to have shorter hind legs than frogs and drier skin, but not always. Most Anura live near water and/or damp areas, but some have adapted to life in trees, like the South American tree frogs, or in deserts. They can be found worldwide, except in polar regions.

Caudata is the group for salamanders. Although they resemble lizards, they are not related. Salamanders are elongated with short legs, have no claws, smooth skin without scales, and tails that are usually flattened from side to side and may have fins. They also can regrow their tails. Most are under 6 inches, or 15 centimeters, in length. They may live either on land or in water, and many spend parts of each year in both habitats.

Gymnophiona is comprised of caecilians. These animals are long, cylindrical, and limbless, similar to a snake or worm. Most are between 3-30 inches, or 8-75 cm, in length. The Thompson's caecilian can grow up to almost 5 feet, or 150 cm, in length. Their skin has folds, and a few have tiny scales. Their eyes are covered with skin, and their eyesight is poor. Most live underground in damp soil, but some live in water. Most lay eggs underground, and the larva make their way to nearby water once they hatch. They are found in tropical Africa, Asia, and Central and South America.

Roles

Amphibians play important roles, particularly in their reactions to the state of their environment. They are considered to be good indicators of environmental health because their skin easily absorbs poisons from the air, water, and soil. They require specific habitats, so they are not able to move away from changes that disturb them. They are easily affected by habitat destruction, over-exploitation (such as too many people wanting to eat frog legs), pollution, climate change, and destruction to the ozone layer, which causes damage to their eyes, eggs, and skin.

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