Skin Breathing Characteristics and Examples of Animals

The skin respiration it is a form of respiration in which gas exchange occurs through the skin and not through the lungs or gills. This process occurs mainly in insects, amphibians, fish, sea snakes, turtles and some mammals (Jabde, 2005).

The skin of animals that use cutaneous respiration is quite special. To allow gas exchange to take place, it must be humid so that both oxygen and carbon dioxide can pass freely through it..

Article index

• 1 Features
• 2 Cutaneous respiration in different classes of animals
  • 2.1 Amphibians
• 3 Reptiles
• 4 Mammals
• 5 Insects
• 6 Fish
• 7 References

Characteristics

The cutaneous respiration process is carried out solely through the skin. For this reason, the majority of vertebrate animals that use this type of respiration, the skin is highly vascularized in order to facilitate the process of gas exchange..

This exchange is highly important in amphibians and softshell turtles, which use mucous glands to conserve moisture in the skin (Marshall, 1980)..

Some amphibians have many folds in their skin that help increase their respiratory rate. Toads are known to take in water and breathe through their skin. They have three forms of respiration: cutaneous, pulmonary and through the lining of the mouth. This last type of respiration is the most used when they are in a state of rest..

Skin breathing is a type of breathing that does not require the lungs to take place. For this reason, there are species that lack lungs and can still survive thanks to the gas exchange carried out through the skin..

There are species that can exert both cutaneous and pulmonary respiration, however, it is estimated that in amphibians cutaneous respiration is responsible for taking 90% of the oxygen necessary to live.

Cutaneous respiration in the different classes of animals

Amphibians

The skin of all amphibian species is the organ most used to carry out the breathing process. Some species depend solely on skin respiration to survive.

This is the case of the plumed salamander of the family Plethodontidae. This family of amphibians completely lacks lungs, however, it makes up the largest group of salamander species in the world. (Zahn, 2012)

While amphibians are completely submerged in water, cutaneous respiration takes place through their skin. This is a porous membrane through which the air spreads between the blood vessels and everything that surrounds them..

Although cutaneous respiration is predominant in amphibians, it only helps toad survival during colder seasons.

Skin respiration requires constant moisture on the surface of the skin. When the toads are out of the water, the mucous glands in the skin continue to moisten the skin, which allows a process of absorbing oxygen from the air..

There are some special cases in the respiration of amphibians. For example, tadpoles, which breathe through gills, and desert toads, which tend to have dry skin, making skin respiration unfeasible (Bosch, 2016).

Reptiles

The scales that cover the reptile's body prevent, in most cases, a skin respiration process from taking place. However, there is the possibility of a gas exchange between the scales or areas where the density of scales is lower..

During periods of underwater hibernation, some turtles depend on skin respiration around the cloaca to survive.

Similarly, there are species of sea snakes that take approximately 30% of the oxygen they need through the skin. This becomes essential when they need to go underwater..

For sea snakes it is possible to carry out this process by decreasing the intensity with which the blood supplies the lungs and increasing the blood supply in the capillaries of the skin. For this reason, snake skin can sometimes appear pink. (Feder & Burggren, 1985)

Mammals

Mammals are known to be endothermic or "warm-blooded" species. They generally have a higher metabolic demand than exothermic or so-called "cold-blooded" vertebrate animals..

Similarly, the skin of mammals is thicker and more impermeable than that of other vertebrate species, which greatly prevents the skin from being the organ used to carry out the gas exchange process..

However, cutaneous respiration in mammals exists, but it occurs in a lower percentage. An example is bats, which take in oxygen through the highly vascular membranes located on their wings. Bats can take in about 12% of the oxygen they need through their wings.

Humans are among the mammalian species that take the lowest percentage of oxygen from the air through the skin. A human being can take on average between 1% and 2% of oxygen from the air, with which he could not ensure his subsistence (Ernstene & Volk, 1932).

Insects

In insects, gas exchange through the skin tends to be generous, but it is not the main source of oxygen uptake..

Most insects take in oxygen and release carbon dioxide through a tissue known as the cuticle, which is located in the outermost part of the epidermis of invertebrates..

There are some families of insects that do not have a defined respiratory system, so they depend completely on skin respiration to transport the hemolymph (similar to the blood in insects) from the surface of the body to the internal tissues.

Most terrestrial insects use a tracheal system to carry out gas exchange. However, in aquatic and endoparasitic insects, skin respiration is vital, since their tracheal system cannot supply the necessary oxygen on its own (Chapman, 1998).

Fishes

Cutaneous respiration takes place in different species of marine and freshwater fish. For aquatic respiration, fish mainly require the use of gills.

However, skin respiration represents between 5% and 40% of the total oxygen uptake from water, although all this depends on the species and the temperature of the environment..

Skin respiration is more important in species that take oxygen from the air such as jumping fish or coral fish. In these species, oxygen uptake through the skin represents 50% of total respiration.

References

1. Bosch, D. L. (7 of 2 of 2016). All you need is Biology. Retrieved from How To Breathe Without Lungs, Lissamphibian Style: allyouneedisbiology.wordpress.com.
2. Chapman, R. F. (1998). Cutaneus Respiration. In R. F. Chapman, The Insects: Structure and Function (p. 452). New York: Cambridge University Press.
3. Ernstene, A. C., & Volk, M. C. (1932). The Effect of Venous Congestion on the Rate of Carbon Dioxide Elimination and Oxygen Absorption. The Journal of Clinical Investigation, 387-390.
4. Feder, M. E., & Burggren, W. W. (1985). Cutaneous Gas Exchange In Vertebrates: Design, Patterns, Control And Implications. Biological Reviews, 1-45.
5. Jabde, P. V. (2005). Respriation. In P. V. Jabde, Text Book Of General Physiology (p. 112). New Dehli: Discovery Publishing House.
6. Marshall, P. T. (1980). Respriation, Gas Exchange and Transport. In P. T. Marshall, Physiology of Mammals and Other Vertebrates (pp. 88-89). New York: Cambridge University Press.
7. Zahn, N. (24 of 8 of 2012). Obtained from Salameandering Into Cutaneous Respiration: iheartungulates.com.