14 ANIMALS THAT BREATHE THROUGH THE SKIN (CUTANEOUS RESPIRATION) - BIOLOGY - 2025

The animals breathe through the skin (dermal respiration) they are all those animals that have the ability to perform their respiratory process cutaneously. They therefore differ from animals that have pulmonary or gill respiration.

Among this group are amphibians (frogs, toads, salamanders), annelids (earthworms) and some echinoderms (sea urchins). However, some fish, snakes, turtles and lizards use their skin as a respiratory organ to a greater or lesser degree.

The skin of these animals is moist, quite thin and highly vascularized in its inner layers. These characteristics are essential in this type of animal to allow the respiratory process through this organ.

Additionally, most animals with this type of respiration have lungs or gills that provide an alternate surface for gas exchange and that supplements skin respiration. In fact, only certain types of salamanders, which have neither lungs nor gills, survive on skin respiration alone.

14 examples of animals that breathe through skin

Annelids

1- The earthworm

The earthworm is an animal that belongs to the annelid family. They are given this name due to the distinctive feature of their body being divided into ring-like segments.

To feed, it makes tunnels in the ground. By doing this, organic material passes through your digestive tract and then removes the waste in the form of excrement. This constant activity of the earthworm makes it possible to soften, enrich and aerate the soils.

This animal lacks special respiratory organs, so its breathing process is carried out by simple diffusion through its skin.

2- Leech

The leech is a flattened-bodied animal that has suction cups at each end of its body. Most species of this animal feed on blood that they suck from other organisms.

They breathe through their skin, although in some families (Piscicolidea) of these annelids the presence of small gills similar to lateral branches is observed on their body.

In the Gnatobdelida and Pharyngobdelida families, the presence of a red pigment known as extracellular hemoglobin is also observed, which carries 50% of the oxygen absorbed by these animals.

3- Korean or nereis worm

The Korean or nereis earthworm is a marine worm belonging to the annelid family, specifically the polychaete class. Its body is elongated, semi-cylindrical and with ring-shaped segments. It has four eyes and powerful claw-like jaws that help it catch its prey.

The nereis lacks specialized respiratory organs. Therefore, it breathes through the entire surface of its body, but more specifically through the flat, thin appendages that laterally border its body.

Amphibians

4- Axolotl

The axolotl or axolotl is a type of salamander from the amphibian group that is found almost exclusively in the region of the Valley of Mexico, specifically in the Xochimilco channel system. Although some species are also found in North America.

Like most salamanders, it has the appearance of a lizard. Their skin is smooth, glandular and moist. They are of different colors (brown, black, green, with spots, yellow).

Some pink and completely white specimens have been found (albino axolotls). It carries out its breathing process in three ways: gills, lungs, and skin.

5- Frogs

Frogs belong to the group of amphibians known as anurans. They are animals that undergo a process of metamorphosis from birth to adulthood.

In their early stages of development, they are known by the name of tadpoles and live exclusively in aqueous environments. At this stage, their respiration is gill and cutaneous.

Pulmonary and skin respiration occurs in adult animals. The two types of breathing alternate according to the time of year. For example, during winter, oxygen requirements are lower, therefore, the greatest uptake is through the skin.

On the contrary, during the summer, the demand for oxygen is greater and the uptake of it is done mainly through the lungs. However, the two forms of breathing work alternately to a greater or lesser extent.

6- Cecilia

The caecilian is a limbless (legless) amphibian shaped like a worm. Some do not have a tail and others have a rudimentary one. Some caecilians have rudimentary lungs that complement breathing through the skin.

However, recently, species have been discovered that completely lack lungs and whose respiration is entirely cutaneous. Caecilia live in humid tropics and in watery environments.

7- Jalapa false newt

The false newt jalapa is a type of salamander that belongs to the group of lungless salamanders. Its body is elongated, it has bulging eyes and a long tail. Because they lack lungs, their breathing is completely cutaneous.

8- Toads

Toads, like frogs, belong to the group of anurans. They differ from these in terms of their size, length of the legs, texture of the skin (rough in toads, smooth in frogs) and in their way of moving (frogs do it by making long jumps, toads do it by giving small jumps or walking).

Toads also present the same types of respiration as frogs throughout their development. However, in their adult state, and because their skin is drier, they are more dependent on lung respiration.

9- Triton

Newts are amphibians that belong to the same family as salamanders. Their body is thin and elongated and they have short legs. Its tail is long and flattened.

They tend to be smaller than salamanders and, unlike salamanders, spend most of their lives in water. Like most amphibians, they carry out much of their breathing through their skin.

Echinoderms

10- Sea urchins

Sea urchins are a class that belongs to the echinoderm family. They are generally balloon-shaped and have no limbs. Its internal skeleton is covered only by the epidermis.

They have movable spines around their entire body, which allow them to move around and provide a method of defense against predators. It has two types of respiration: branchial and cutaneous.

11- Sea cucumber

The sea cucumber belongs to the echinoderm family. Its body is elongated and soft, similar to that of a worm and lacks limbs. It has the mouth in the front part and the orifice of the anus in the back part.

Its size varies from a few millimeters to several meters. Several species have branched tubes close to the anus that help them breathe, although they also breathe through their skin.

12- Mediterranean Comatula

These animals belong to the species known as sea lilies and are part of the echinoderm family. Its body is shaped like a chalice, from which 5 arms project which in turn have smaller bifurcations.

The respiration process occurs through the contact of the integument with the aqueous medium, mainly by the undulatory movement of the ambulatory canal.

13- Ofiura

They are a class of animals that belongs to the echinoderm family. Its body is made up of a rounded and flattened central structure from which very thin and long arms emerge that present small branches. To move, it uses its arms moving them in an undulating way like snakes.

Like other echinoderms, they have incipient respiratory systems and most of the gas exchange occurs through skin respiration.

14- Tobacco Box

It is a type of sea urchin. Its body is covered by a shell of calcareous layers. Thin filaments (known as spikes) protrude through the pores of the shell to help them move and protect themselves. It has gill and cutaneous respiration.

Reptiles and Mammals with skin respiration

In some reptiles a certain degree of integumentary gas exchange can be seen, although this does not indicate that they are animals with skin respiration. Simply that, under certain circumstances, for some animal species skin respiration is an alternative for gas exchange.

Some of these reptiles are the sea snake (it releases about 40% of carbon dioxide through the skin), the musky turtle (it captures about 35% of oxygen and releases 25% of carbon dioxide from the skin), the green lizard. (20% oxygen and 15% carbon dioxide through the skin) and the Japanese turtle (15% oxygen and 10% carbon dioxide through the skin), among others.

In the same way, it has been found that even in some mammals, cutaneous gas exchange contributes considerable values ​​to the gas exchange rate necessary for the subsistence of the animal.

An example of this is found in the brown bat, which obtains approximately 13% of its oxygen requirement through its skin and eliminates about 5% of the carbon dioxide by this same means.

Some facts about skin respiration

The cutaneous respiratory process is carried out through the corporal integument which is the organ that externally covers the multicellular organisms (formed by the skin and the appendages or cutaneous attachments).

For this process to occur, it is necessary that the cuticle of the epidermis (which is the outermost layer of the skin) is moist and quite thin.

Skin moisture is achieved by the presence of glandular cells that are intercalated between the cuboidal cells of the epithelium. These cells produce mucus that covers the entire skin and provide it with the necessary moisture for gas exchange.

Another important characteristic that facilitates this type of respiration is the presence under the epidermis of abundant blood capillaries that contribute to gas exchange.

The process begins with the uptake of oxygen by diffusion through the skin. From there it passes to the blood vessels and through the blood reaches the cells where a new gas exchange takes place by diffusion.

The blood collects carbon dioxide gas that is released back into the environment through the skin. In this way the respiratory cycle is completed. In essence, the process is similar to other animals with more complex respiratory systems.

Animals with skin respiration live in watery habitats or in humid soils, which allows them to keep their skin lubricated, a condition that is essential for the respiratory process.

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