How do Amphibians breathe? – (Explained in Detail)
Introduction to Amphibians
Amphibians are the freshwater or semi-aquatic, air and water breathing vertebrate animals that are cold-blooded.
Their body is divisible into head and trunk. Neck and tail may be absent or present.
Popular well-known amphibians include frogs, toads, salamanders, caecilians, caudata, newts, etc.
They have four limbs of pentadactyle type, that is with each limb bearing 5 clawless digits. Some are limbless too.
Their skin is smooth or rough and is always rich in glands keeping it moist. Their special skin glands can also produce useful proteins.
They also have a bony endoskeleton.
Respiration in Amphibians takes place by lungs, skin surface, and through the buccal cavity lining.
They also use gills to breathe during their larval stages of development. Gills disappear in adults and can be present in some aquatic adults.
During their early stages of embryonic development, they usually live in water and when they grow and enter the adult phase they can survive in both land and water.
They are all cold-blooded. Meaning that their bodies can’t regulate their body temperature. In fact, they need to cool off and warm up by using their surroundings.
Adult amphibians are carnivores and predators. They eat a variety of food including spiders, beetles, and worms.
During the early stages of development the larvae of many amphibians mostly feed on the aquatic plants.
Breathing Vs. Respiration in Amphibians
Breathing is a biophysical process, whereas respiration is a biochemical process.
Biophysics applies the theories and methods of physics to explain the physical working of the biological body.
Whereas, the biochemical process explains the chemical processes and transformations happening inside the living organisms’ cells.
Breathing in Amphibians explains how the organism uses its skin, gills, lungs, and buccal cavity lining to inhale oxygen and exhale carbon dioxide by various biophysical or biomechanical methods.
So in simple words, breathing is a biophysical process that involves the exchange of gases through inhalation and exhalation.
Respiration in Amphibians explains how the complex organic compounds are broken down into carbon dioxide and water while releasing energy, all inside the cells.
So in simple words, respiration is a biochemical process to release energy (ATP) from organic compounds (like Glucose) which are then used for performing different physical activities.
Breathing is ‘external respiration’ and Respiration is ‘internal respiration’.
Breathing consists of two steps viz. Inhalation and Exhalation. Whereas, respiration consists of three steps viz. Glycolysis, Kreb’s cycle, and Electron transport chain.
Breathing doesn’t provide energy. On the other hand, respiration results in the production of energy.
How do Amphibians breathe?
The breathing and respiratory organs of amphibians include their lungs, skin, the buccal cavity lining, and of course their gills.
A majority of the amphibians breathe by means of gills during their tadpole larval stages, and by using their lungs, skin, and buccal cavity lining when they have become adults.
When in water, they use their skin and buccal cavity lining to breathe and respire. And, when on lands, they use their lungs to breathe and respire.
Gills are present at least during their early stages of larval development. And as the tadpole larva of the amphibian matures, the gills are absorbed by the body and replaces with its buccal cavity lining.
1. Using Their Skin: How do Amphibians breathe using their skin?
Amphibians use their moist skin to breathe. Their skin has numerous skin glands that secretes various proteins and mucus that helps keep the skin moist.
Skin is their most important and largest organ. Their skin is thin and allows the exchange of carbon dioxide and oxygen in and out of the body. Thus, helping in overall breathing and respiration.
They use their moist skin to breathe underwater. They don’t use their lungs to breathe underwater, or else if their lungs get filled with water, they can drown very easily.
It is also to be noted that it is very much important for them to keep their skin moist. So you’ll often find the moist skin ones in damp areas.
Or else, if their skin gets too dry, then they cannot breathe and will die very easily.
So, it is of utmost importance for them to stay wet in order for them to absorb oxygen. So they secrete mucus to keep their skin moist.
They use their skin to absorb dissolved oxygen into their skin when underwater, and remove carbon dioxide out through their skin that gets dissolved in the water. All this happens by simple diffusion-based on gradient concentration.
If the concentration of oxygen in the skin region is low then the surrounding water, then dissolved oxygen in the water gets escaped into the body of the amphibian through the skin surface.
Then the oxygen easily gets diffused into the blood and gets transported to the whole body. The released Carbon dioxide from the cells is now carried via the blood in the blood vessels to the outer skin surface.
Here, on the skin surface, as the concentration of carbon dioxide is greater than the outer surrounding water, therefore the carbon dioxide in the cells gets released and gets dissolved into the open water.
Also on land, they use their wet and moist skin, their buccal cavity lining, and also a pair of their lungs to breathe.
2. Using Their Lungs: How do Amphibians breathe using their lungs?
Amphibians use their lungs to breathe when they are on land.
Some amphibians can stay for longer periods on land by breathing through lungs, while others need to go underwater after some time.
The lungs of amphibians are very poorly developed and are simple saclike structures. They are not spongy types just like the higher mammals like us.
To breathe using lungs they use their nostrils and mouth to intake oxygenated air by inspiration.
The intaken air enters and leaves the mouth towards the lungs through the respiratory tract that connects the two lungs together, one at each end-branch of the tract.
On the surface of the lungs, there are cells that are connected with very thin blood vessels between which the exchange of gases takes place by diffusion.
The deoxygenated air that comes out of the lungs gets into the mouth through the respiratory tract by expiration.
To eliminate the carbon dioxide out from the lungs the nostrils need to be opened and the floor of the mouth needs to be moved up pushing the air out of the nostrils.
The lungs of most amphibians receive a large proportion of the total blood flow from the heart, due to which simple diffusion takes place and the exchange of oxygen and carbon dioxide between the lung surface and the blood takes place.
3. Using Their Buccal Cavity lining: How do Amphibians breathe using their buccal cavity lining?
Amphibians can also use the lining of their buccal cavity to exchange oxygen and carbon dioxide gas very easily by diffusion. The skin layer of their buccal cavity lining is very thin.
The location of the buccal cavity lining was the spot where the gills were present during the tadpole stage of the amphibians like frogs, etc.
This lining has numerous blood vessels through which the diffusion of oxygen in and carbon dioxide out of the blood and the buccal lining takes place.
Same like the breathing through the skin, the buccal cavity lining works almost in the same way.
They can also perform buccal respiration using the buccal cavity. Breathing occurs by lowering and raising the floor of the buccal cavity, during the course of which the air is being constantly sucked into the buccal cavity and transferred towards the lungs.
During exhalation, the air coming out of the lungs is drawn out through the external and internal nostril.
4. Using Their Gills: How do Amphibians breathe using their gills?
A tadpole is a larval stage in the life cycle of an Amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial.
The aquatic or semi-aquatic tadpoles have gills during their initial stages of development. Tadpoles are born with gills, just like a fish, so that they can breathe underwater.
Tadpoles have tiny external gill flaps that extract oxygen from water as it passes over them. Tadpoles exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills.
In very simple words, tadpoles open their mouths as they swim and take in water. As the mouth closes, the water gets transferred to the gills and eventually out through it.
Each filament of the tadpole’s gills contains a minute capillary network that provides a large surface area for exchanging oxygen and carbon dioxide.
This capillary network takes the oxygen from the water where it enters the bloodstream through the process of diffusion.
Tadpoles can also rise to the surface and take oxygen from the air and fill it in their mouth.
It is also to be noted that the tadpoles can also breathe using their tail surface. Their tail has a lot of blood capillaries in it that help to exchange the gases between the water and the body’s blood.
Do Amphibians breathe both on land and in the water?
Yes, by now it is very clear that amphibians can breathe both on land and in water.
The larvae live in water and breathe using their gills. On, the other hand the adults can live and breathe both on land and underwater for part of the time.
But, for how long they can breathe inside water and outside of water depends from species to species.
Just, for instance, frogs remain half of their time in the damp areas near the water bodies and another halftime underwater in the ponds, or in other stagnant water bodies.
On the other case, toads remain most of the time of the year out of water in both dry and damp types of places. They are only noticed to go inside water for breeding and laying eggs.
Amphibians are not marine animals so they are only known to live in land and freshwater only. Their larval youngsters, which are known as tadpoles, also don’t inhabit oceans.
Amphibians can’t live in marine or ocean water because, ocean water contains lots of salt in it.
And, we all know that amphibians must have moist skin in order to breathe and stay alive. So, if they try to live in ocean water their skin will intake too much salt while losing too much water due to osmosis.
Thus, this will lead to the drying up of their skin due to excessive loss of water, leading to their death.
So, all species of amphibians known to date are all freshwater species and none of them are marine.
Also, for the purpose of reproduction and laying of eggs most amphibians require freshwater, so the mostly terrestrial ones also need to go inside water for sometime during the year.
Some species have also developed ways to lay their eggs on land while keeping them moist.
While, a few of the species like the Crab-eating Frog (Fejervarya raja) can inhabit brackish (slightly salty) water, but there are no true marine amphibians.