How Do Amphibians Breathe?

Amphibians are a fascinating group of animals. They’re ancient, dating back approximately 370 million years to the Devonian period, predating reptiles by millions of years. In fact, they were the first vertebrates to venture onto land hundreds of millions of years ago and for a long time, they were the dominant group of animals on the planet.

Their unique hybrid lifestyle, both aquatic and terrestrial, means that people have lots of questions about them. Most of these questions revolve around one of the most interesting things about amphibians: how they manage to breathe in the air and in the water.

How Do Amphibians Breathe?

Amphibians have a unique respiratory system that doesn’t rely entirely on a single source of oxygen. In addition to their lungs, amphibians can actually breathe through their skin. As long as their skin is moist, they can absorb oxygen directly from the air or water through the skin. For example, many species of frogs and salamanders heavily rely on this method of respiration.

This is why amphibians typically secrete a lot of mucus, to keep their skin moist and ensure they can breathe. The Green Frog and other similar species are known for producing ample mucus to maintain moisture. It’s also why most amphibians live only in wet, humid environments. If their skin dries out too much, they won’t be able to breathe. Their lungs aren’t enough to keep them alive on their own.

This is also why amphibians can stay underwater for so long. Just as their skin can absorb oxygen from the air, it can absorb oxygen from the water, too. While this method of breathing underwater isn’t as effective as gills, it still works quite well for extended periods.

Because they breathe through their skin, extreme care must be exercised when handling an amphibian. The skin is highly permeable, and any contaminants on your hands will penetrate their skin easily. This also makes them highly vulnerable to pollutants such as pesticides, chemicals, and other environmental toxins.

In addition to their skin, most amphibians also use the lining of their mouth to breathe. In fact, when they’re not underwater, the mouth is in almost constant use for breathing. This process, known as buccal respiration, helps them draw in additional oxygen.

Do All Amphibians Have Lungs?

Again, some do, some don’t. More accurately, most do, a few don’t. The fully aquatic salamanders typically don’t develop lungs, but almost all other amphibians do develop them as they grow from tadpoles into adults. The giant salamander species, such as the Japanese Giant Salamander, are fully aquatic and spend their whole lives underwater.

Their lungs are quite a bit simpler in structure than the lungs of most air-breathing animals, and this is a large part of what keeps them so dependent on the water. While they can breathe air, most amphibians aren’t capable of using their lungs for breathing exclusively.

There are some salamanders, called the lungless salamanders, that have no lungs and rely entirely on their skin to breathe. In addition, some species of fully aquatic salamanders, which have gills, don’t grow lungs either.

Do Any Amphibians Have Gills?

Some do, and some don’t. There are several species of salamander, such as the axolotl, which live fully aquatic lives and have large external gills. These species, while they are amphibians, can’t live truly amphibious lives and remain in water throughout their life.

Many, if not most, amphibians have gills of some sort during their tadpole phase. During this stage of their lives, all amphibians are fully aquatic, and the most efficient way for them to breathe is to use gills. For example, American Bullfrog tadpoles have gills that they lose as they develop into adults.

While these gills are functionally the same as fish gills, they are structurally quite different. They consist of a single stalk of flesh lined with dozens or hundreds of small, blood-vessel-filled filaments that facilitate gas exchange. Each of these stalks can be moved around as an appendage, which stirs the water and helps prevent a build-up of oxygen-depleted water around the gills that could occur in still or stagnant water.

How Long Can Amphibians Hold Their Breath?

Since amphibians don’t rely entirely on their lungs or on air-breathing in general, they can hold their breath for an impressive amount of time. The exact amount of time will depend on the species, but 4-7 hours is typical for most frogs and many other amphibians. For some species, they can hold their breath even longer under ideal conditions.

Do Amphibians Breathe Air or Water?

Both! On land, amphibians breathe air. Underwater, they breathe through their skin by absorbing oxygen from the water. Their respiratory systems are unique in their ability to pull oxygen out of both air and water, and this versatility is one reason why amphibians, one of the oldest groups of vertebrates on the planet, are still around.

However, while their ability to breathe both underwater and in the air is incredible, their respiratory system does have its flaws. They aren’t as efficient at breathing air as reptiles, mammals, or birds, and they aren’t as effective at breathing underwater as fish.

This is part of why amphibians today tend to be smaller animals—it’s hard for them to grow any bigger with an inefficient respiratory system.

Can All Amphibians Breathe Underwater?

No, not all amphibians can breathe underwater. Some species are able to respirate through their skin when completely submerged, although they can still hold their breath for an impressive amount of time.