amphibians were probably the step that evolution took to colonize the earth's surface with animals. Until then, they were held captive in the seas and oceans, because the earth had a very toxic atmosphere. At a certain point, some animals began to come out. For this, adaptive changes had to appear that allowed the breathing of air instead of water. In this article on our site we talk about amphibian respiration. Do you want to know where and how amphibians breathe? We tell you!
What are amphibians?
Amphibians are a large phylum of tetrapod vertebrate animals that, unlike other vertebrate animals, undergo metamorphosis throughout their life that causes them to have several mechanisms to breathe.
Types of amphibians
Amphibians are classified into three orders:
- Order Gymnophiona, which are the caecilians. They are shaped like a worm with four very short limbs.
- Cadata Order. They are the urodeles or amphibians with a tail. Salamanders and newts are classified here.
- AnuraOrder. They are commonly known as frogs and toads. They are amphibians without tails.
Characteristics of amphibians
Amphibians are vertebrate animals poikilotherms, that is, their body temperature is regulated according to the environment. Therefore, these animals usually live in warm or temperate climates.
The most important characteristic of this group of animals is that they undergo a very abrupt transformation process called metamorphosis The reproduction of amphibians is sexual, after laying the eggs and after a certain time, some larvae come out of them that have little or nothing to do with the adult specimen and are of aquatic life. During this period they are called tadpoles and breathe through gills and through their skin. After metamorphosis, developing lungs, limbs and sometimes losing their tails (this is the case of frogs and toads).
They have a very thin and moist skin. Despite being the first animals to colonize the earth's surface, they are still closely linked to water. This thin skin allows gaseous exchange throughout the life of the animal.
Where do amphibians breathe?
Amphibians, throughout their lives, use various breathing strategies. This is because the environment in which they live, before and after metamorphosis, is very different, although they are always closely linked to water or humidity.
During their larval stage, amphibians are aquatic animals and live in freshwater areas such as ephemeral ponds, lagoons, lakes, rivers of clean and clear waters and even swimming pools. After metamorphosis, the vast majority of amphibians become terrestrial animals and, although some constantly enter and leave the water to stay moist and hydrated, others are capable of keep your body moist simply by protecting yourself from the sun.
So, we can observe four types of respiration in amphibians:
- Gill respiration.
- Mechanism of the oropharyngeal cavity.
- Breathing through the skin or integuments.
- Lung respiration.
How do amphibians breathe?
The way amphibians breathe changes from one stage to another, and there are also some differences between species.
1. Amphibian respiration using gills
After hatching and until metamorphosis, tadpoles breathe through gills on both sides of their heads. In the species of anurans, frogs and toads, these gills are hidden in gill sacs and, in urodeles, that is, salamanders and newts, they are totally exposed to the outside. These gills are very irrigated by the circulatory system, they also have a very thin skin that allows gaseous exchange between the blood and the environment.
two. Bucco-pharyngeal respiration of amphibians
In salamanders and some adult anurans, inside the mouth there are bucco-pharyngeal membranes that act as respiratory surfaces. In this respiration, the animal takes in air and holds it in its mouth, meanwhile, these membranes, highly permeable to oxygen and carbon dioxide, carry out gas exchange.
3. Amphibian respiration through the skin or integuments
Amphibians' skin is very thin and unprotected, so they need it to be always moist. This is because they can perform gas exchange through this organ. When they are tadpoles, respiration through the skin is very important and they combine it with gill respirationUpon reaching adulthood, it has been found that oxygen uptake is minimal but carbon dioxide expulsion is high.
4. Lung respiration in amphibians
During amphibian metamorphosis, the gills gradually disappear and lungs develop to give adult amphibians the possibility to step onto solid ground. In this type of breathing, the animal opens its mouth, lowers the floor of the oral cavity, and air enters. Meanwhile, the glottis, which is a membrane that connects the pharynx with the trachea, remains closed and, therefore, there is no access to the lung. This is repeated several times.
In the next step, the glottis is opened and, by a contraction of the chest cavity, the air in the lungs from the previous breath is expelled through the mouth and nostrils. The floor of the oral cavity rises and pushes the air into the lungs, the glottis closes and the gas exchange occursSome time usually passes between one respiratory process and another.
Examples of amphibians
Below we show you a small list with some examples of the more than 7,000 species of amphibians that exist in the world:
- Thompson's Cecilia (Caecilia thompsoni)
- Caecilia pachynema (Typhlonectes compressicauda)
- Mexican caecilian (Dermophis mexicanus)
- Tapiera snake (Siphonops annulatus)
- Ceylon caecilian (Ichthyophis glutinosus)
- Chinese giant salamander (Andrias davidianus)
- Fire salamander (Salamandra salamandra)
- Tiger Salamander (Ambystoma Tigrinum)
- Northwest salamander (Ambystoma gracile)
- Long-toed salamander (Ambystoma macrodactylum)
- Cave salamander (Eurycea lucifuga)
- Zig-zag salamander (Plethodon dorsal)
- Red-legged salamander (Plethodon shermani)
- Iberian Newt (Triturus boscai)
- Crested Newt (Triturus cristatus)
- Marbled Newt (Triturus marmoratus)
- Fire-bellied Newt (Cynops orientalis)
- Axolotl (Ambystoma mexicanum)
- East American Newt (Notophthalmus viridescens)
- Common frog (Pelophylax perezi)
- Poison dart frog (Phyllobates terribilis)
- San Antonio Tree Frog (Hyla arborea)
- Pumpy Tree Frog (Litoria caerulea)
- Harlequin Frog (Atelopus Varius)
- Common Midwife Toad (Alytes obstetricans)
- Green Toad (Bufotes viridis)
- Spiny Toad (Rhinella spinulosa)
- Bullfrog (Lithobates catesbeianus)
- Common Toad (Bufo bufo)
- Raider Toad (Epidalea calamita)
- Cane Toad (Rhinella marina)