Frogs are incredibly fascinating creatures and one of their most notable traits is their ability to live and breathe on land and in water. As a child, I learned how frogs breathe on land and in water, notably because of their metamorphosis.
Although frogs are not born with lungs, frogs develop lungs as a replacement for gills during the froglet stage of metamorphosis. Frogs use their lungs to breathe on land when necessary, but they primarily use their skin for breathing.
While how frogs breathe may differ depending on the frog’s species and their environment, all frogs go through similar metamorphic stages from when they are eggs to develop lungs to be able to breathe on land. Let’s have a look at how frogs develop lungs and use them in conjunction with their skin to breathe.
Frogs Develop Lungs at 16 Weeks of Age
All frogs undergo metamorphic changes as they mature including the development of their lungs at around 16 weeks of age. Since frogs live part of their lives in water and part of their lives on land, they need lungs to breathe. This is the case for arboreal, terrestrial, and aquatic frogs.
Here is a general idea of when frogs develop lungs:
|Frog Metamorphic Phase||Respiratory System||Age|
|Frog Egg||Skin||3 – 25 days|
|2 – 4 years|
Here is more detail about how frog lungs develop:
- Frog Egg: Gills begin to develop
- Young Tadpole: Gills continue developing. Tadpoles use their external gills after 4 weeks. The tadpole has no legs at this stage. Tadpoles breathe through their skin.
- Mature Tadpole: Tadpoles have legs at this stage. They breathe through their internal gills after about 4 months. Tadpoles start developing lungs near the end of the phase.
- Froglet: Froglets develop functional lungs, but aquatic frogs can only breathe on land for short timeframes.
- Adult Frog: Mature frogs can breathe on land using their lungs. But, aquatic frogs still use their skin most of the time.
Frogs develop lungs as they make the transition from fully aquatic and gilled tadpoles to amphibians capable of living on land. The formation of the lungs occurs during the final tadpole metamorphic phase, although how fast this occurs generally depends on the species. But, many subtle respiratory system developments take place throughout the initial metamorphic phases.
Frog Eggs Do Not Have Lungs
The frog life cycle begins with the frog egg or zygote, which gradually grows over time. Most female frogs can produce eggs in the thousands, with some species laying around 10,000 – 30,000 eggs at a time. The frog eggs are laid in clusters, often supported by aquatic vegetation near the surface.
Frog eggs absorb water from the surroundings to create a jelly-like substance, which coats the eggs and protects them during the initial development phase. The developing frogs feed off of the yolk supply during this phase, as the following body parts begin to form:
- Internal organs
- Internal gills
The time it will take for the egg to transform will generally depend on the frog species and environmental conditions, as frog eggs usually transform better within warmer temperatures. Most frog eggs take 3 – 25 days to transform into tadpoles, depending on the species and climate (CTNF).
Tadpoles Breathe Through Their Gills
Tadpoles result from successful metamorphic changes that occur within frog eggs, embodying the aquatic larval stage of all frogs. Depending on the frog species and the climate, tadpoles can take 14 – 16 weeks to develop even further.
They feed off the remaining yolk supply and are fully aquatic during the initial stages of this phase, but the gills are not fully developed. Thus, tadpoles use their skin to breathe. After some time, these tailed tadpoles would have developed a more functional respiratory system, protected by their short and ovular bodies. They can breathe in the following ways:
- Breathe through their external gills after approximately 4 weeks
- Breathe through their internal gills after approximately 4 months
Toward the end of the tadpole metamorphic phase, the tadpoles will begin to form frog-like body parts and features. These changes include the growth of the hind and front legs and frog-like facial features. The tail starts to get absorbed through apoptosis, and they start to develop lungs as they prepare themselves for living on land.
Adult Frogs & Froglets Have Lungs
Frogs no longer have gills once they reach the froglet stage and their gills have generally completely disappeared by the time they are 16 weeks to 3 years old depending on the species and climate.
Froglets are the result of successful metamorphic changes during the tadpole phase. Froglets will have no tail (although they may still have a tail stub that will disappear over time) and will have limbs, internal organs, and much more. Froglets have lungs and are able to breathe out of water.
It can take anywhere between 2 and 4 years for froglets to reach maturity and be able to reproduce, depending on the species and the environmental conditions. Mature adult frogs have fully developed respiratory systems, and their lungs are much stronger than froglets.
More About How Frogs Breathe
There is still plenty of complexity concerning frog respiratory systems since they cannot simply breathe in and out of the lungs like many other animals. Mature aquatic frogs only use their lungs for breathing when it’s necessary and generally stick to breathing through their skin when possible. However, most toads and tree frogs breathe through their lungs since they spend most of their time on land.
Frogs use their skin for breathing thanks to a process called cutaneous respiration. The process is possible since frogs have many blood cells in their permeable skin. Oxygen is diffused through the skin and absorbed into the blood vessels, and the same process is used to remove carbon dioxide from frogs’ bodies. This process is useful in all environments and hibernation since it can use oxygen in water or soil.
Since frogs do not have a diaphragm to store inhaled air, they will use the mouth and nostrils. Frogs will lower their mouths to expand the throat while the nostrils open up to receive oxygen. The oxygen will then be forced into the lungs through this process.
Although frogs can breathe using their lungs once they are mature, their lung capacity is still fairly limited. As a result, mature frogs generally only use their lungs where it is necessary by using their mouth and nostrils to force oxygen into the lungs, and they typically prefer to use their skin for breathing.
Learn more about how frogs breathe in the following guides on our blog:
- How Do Frogs Breathe?
- Can Frogs Drown?
- Can Frogs Survive Saltwater?
- Why Are Frogs Amphibians?
- Will Tap Water Kill Frogs?
- Why Do Frogs Come Out In The Rain?
- Frog Skin: Everything There is to Know
Common Questions About Frog Lungs
Do frogs have gills? Frogs no longer have gills once they reach the froglet stage and their gills have generally completely disappeared by the time they are 16 weeks to 3 years old depending on the species and climate.
how do frogs breathe? Frogs breathe through their skin, gills, or lungs, depending on their life cycle stage, the species, and their environment. Before metamorphosis into an adult frog, tadpoles breathe through their gills.
Do frogs absorb water through their skin? Frogs drink through their skin by absorbing moisture in humid air, rain, soil, and in the water around them. If frogs or toads need more water, they may absorb it through their “drinking patch” located on the surface of their belly that they press into wet areas like small puddles.