Amphibians - Types & Characteristics
Welcome to this page dedicated to amphibians! Animals of the class Amphibia are known for the fact of being able to live in both aquatic and terrestrial habitats. After all, their name comes from the Greek amphibios - amphi meaning "both" and bios meaning "life".
They include frogs, toads, salamanders, and newts. And these animals do live two different lives, as larvae and as adults, going through a spectacular metamorphosis between these two stages.
There are more than 6,000 species of amphibians in the world, some of which, such as the poison dart frogs, exhibiting incredible colors and patterns, revealing they are actually very poisonous.
Let's dive into the interesting world of amphibians, and learn more about their characteristics, their different types, and many other things. Let's go!
6 Characteristics of Amphibians
- Moist and permeable skin: Amphibians’ skin is moist and has no scales, unlike reptiles. Their skin is also thin and permeable, which enables them to absorb oxygen through their skin and stay hydrated. It also implies they need to stay in a humid environment.
- Dual life cycle: Typically, amphibians go through two different phases. They start their life as aquatic larvae breathing through gills and swimming with the help of a tail. They then undergo a metamorphosis, and spend their adult life as terrestrial animals. As adults, they breathe through their skin and lungs, most of the time lose their tails, and have 4 legs.
- Three-chambered heart: Amphibians have a three-chambered heart, separating oxygenated and deoxygenated blood. This separation is not as efficient as with four-chambered hearts that mammals have, which means they have less ability to sustain long, intense physical activity.
- Lay eggs in water: Amphibians lay eggs in water. Eggs then hatch in water and larvae follow their development in water before their metamorphosis into terrestrial adults (see point #2).
- Internal and external egg fertilization: Amphibians’ eggs can be fertilized externally or internally. For frogs, the male fertilizes the eggs externally as the female is releasing them; For salamanders, eggs are fertilized internally.
- Ectothermic: Amphibians are ectothermic. In other words, they are cold-blooded. They are not able to regulate their body temperature internally. Their body temperature depends on the temperature of the environment they are in.
These characteristics are perfectly in line with amphibian’s ability to live both in water and on land, even though they always need certain humidity to survive. Amphibians have an important ecological role, as they play a big part in regulating mosquito and other pests populations.
The 3 Types of Amphibians
The class Amphibia is made of three different orders, namely Anura (frogs and toads), Caudata (salamanders and newts), and Apoda (caecilians). We are now going to take a look at each of them and their most interesting characteristics.
Frogs & Toads (order Anura)
Frogs and toads are found in most parts of the world, excluding the coldest polar regions and some remote islands. They usually move around by hopping or leaping, thanks to their long hind legs.
Toads are often easily recognized for their warty, bumpy skin, while frogs often have smooth, slimy skin. Another difference between frogs and toads is the way they lay their eggs. Frog eggs are usually found in big clusters, while toad eggs are organized in strings.
Salamanders & Newts (order Caudata, or Urodela)
One aspect of members of the order Caudata immediately catches the attention: the presence of a long tail. It is logical when you know that cauda is Latin for “tail”.
Salamanders and newts also have 4 limbs of similar length, unlike frogs and toads which have longer hind legs. They have slender, lizard-like bodies.
Interestingly, they are found almost exclusively in the Northern Hemisphere.
Caecilians (order Apoda)
Caecilians are a much less known group of limbless worm-like, or snake-like amphibians. Their body shape is perfectly adapted to their lifestyle: they mostly live buried in soil.
They are distributed in tropical regions of the Americas, Africa, and Asia. They are predators and feed on animals living in soil like them, such as earthworms.
Frequently Asked Questions About Amphibians
At the larvae stage, amphibians live in water and breathe through gills. At the adult stage, after the metamorphosis, they breathe through their skin and also through their lungs, but with poorer performance than their cutaneous (skin) respiration.
Yes, amphibians have a backbone, they are vertebrates just like mammals, birds, fish, and reptiles.
Typically, amphibians lay their eggs in water. Amphibians’ eggs do not have a shell, and they need to be kept in an aquatic environment. Their eggs are most of the time covered with a jelly-like substance for extra protection and hydration. Some species do lay their eggs on land, but in very moist conditions.
Amphibians have very thin skin that is not waterproof. It is actually designed to enable oxygen and water to go through it. As a result, an amphibian with no access to water would simply dry out, it would not be able to breathe, and it would die.
Amphibians also need water for their reproduction cycle, to lay their eggs, and for their larvae to develop.
That’s why usually, amphibians don’t travel too far from bodies of water.
Amphibians have moist skin, and they need to make sure to keep it moist in order to be able to breathe. The primary way for amphibians to stay moist is to live in aquatic or very moist environments.
Apart from that, amphibians’ skin is also covered with mucous glands, and this mucous also contributes to keeping their skin moist and making skin respiration possible.
Amphibians regularly shed (or slough) their skin, actually more often than reptiles do. This ensures that their skin remains optimally permeable and allows skin respiration. If they didn’t shed, their skin would harden and be less permeable over time.
It may not look like it at first glance, but yes, amphibians have teeth. While some species are toothless, most of them have tiny teeth, usually on the upper jaw. A study by the Florida Museum of Natural History revealed that most frogs actually lost and regained their teeth more than 20 times over the course of evolution!
Learn More About Amphibian Species
Links to articles packed with surprising facts and knowledge to further learn about amazing species of amphibians, so you know what you are looking at on your next wildlife trip!
