Cutaneous respiration

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Cutaneous respiration, or cutaneous gas exchange (sometimes called skinbreathing), [1] is a form of respiration in which gas exchange occurs across the skin or outer integument of an organism rather than gills or lungs. Cutaneous respiration may be the sole method of gas exchange, or may accompany other forms, such as ventilation. Cutaneous respiration occurs in a wide variety of organisms, including insects, amphibians, fish, sea snakes, turtles, and to a lesser extent in mammals.

Contents

Physical constraints

Gas exchange in cutaneous respiration is controlled by three factors: [2]

Taxonomic diversity in chordates

Fish

Cutaneous respiration occurs in a variety of marine, intertidal, and freshwater fish. For aquatic respiration, fish respire primarily via gills but cutaneous respiration may account for 5 to 40 percent of the total respiration, depending on species and temperature. Cutaneous respiration is more important in species that breathe air, such as mudskippers and reedfish, and in such species may account for almost 50 percent of total respiration. [2]

Amphibians

The prominent skin folds of Telmatobius culeus increase surface area for cutaneous gas exchange Telmatobius culeus.jpg
The prominent skin folds of Telmatobius culeus increase surface area for cutaneous gas exchange

The skin of amphibians is a major site of respiration in all species for which measurements are available. [2] Cutaneous respiration is the sole respiratory mode of lungless salamanders (family Plethodontidae) which lack lungs entirely yet constitute the largest family of salamanders. Cutaneous respiration in frogs and other amphibians may be the primary respiratory mode during colder temperatures. [3]

Some amphibians utilizing cutaneous respiration have extensive folds of skin to increase the rate of respiration. Examples include the hellbender salamander and the Lake Titicaca water frog. [2] Cutaneous respiration in hellbenders accounts for more than 90 percent of oxygen uptake and carbon dioxide excretion. [4]

Reptiles

Being covered in scales largely precludes cutaneous respiration in reptiles, but gas exchange may occur between scales or areas with reduced scales. Some turtles rely on cutaneous respiration from enteral respiration around the cloaca during underwater hibernation. [4]

In some sea snakes, cutaneous respiration can account for up to 30 percent of total oxygen uptake and is important when diving, during which blood is shunted away from the lungs and towards capillaries in the skin, in some cases causing the skin to turn pink. [2]

Mammals

Mammals are endotherms, ("warm-blooded") and have higher metabolic demands than ectothermic ("cold-blooded") vertebrates, and the skin is thicker and more impermeable than other vertebrates, which preclude the skin as a major source of gas exchange. However, small amounts of respiration may occur, and in bats, the highly vascularized wings may account for up to 12 percent of carbon dioxide excretion. [4] In humans and most other mammals, cutaneous respiration accounts for only 1 to 2 percent. [4] [2] A lot more respiration occurs through the skin in newborn marsupials. In the Julia Creek dunnart the newborns are extremely small, and 95% of their gas exchange happens via their skin. [5]

See also

Related Research Articles

<span class="mw-page-title-main">Amphibian</span> Class of ectothermic tetrapods

Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all tetrapods excluding the amniotes. All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura, Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems. Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this.

<span class="mw-page-title-main">Hellbender</span> Species of amphibian

The hellbender, also known as the hellbender salamander, is a species of aquatic giant salamander endemic to the eastern and central United States. It is the largest salamander in North America. A member of the family Cryptobranchidae, the hellbender is the only extant member of the genus Cryptobranchus. Other closely related salamanders in the same family are in the genus Andrias, which contains the Japanese and Chinese giant salamanders. The hellbender is much larger than any other salamander in its geographic range, and employs an unusual adaption for respiration through cutaneous gas exchange via capillaries found in its lateral skin folds. It fills a particular niche – both as a predator and prey – in its ecosystem, which either it or its ancestors have occupied for around 65 million years. The species is listed as Vulnerable on the IUCN Red List of Threatened Species due to the impacts of disease and widespread habitat loss and degradation throughout much of its range.

<span class="mw-page-title-main">Skin</span> Soft outer covering organ of vertebrates

Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.

<span class="mw-page-title-main">Salamander</span> Order of amphibians

Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela from the group Caudata. Urodela is a scientific Latin term based on the Ancient Greek οὐρά δήλη: ourà dēlē "conspicuous tail". Caudata is the Latin for "tailed ones", from cauda: "tail".

<span class="mw-page-title-main">Lung</span> Primary organ of the respiratory system

The lungs are the main organs of the respiratory system in many terrestrial animals, including all tetrapod vertebrates and a small number of amphibious fish, pulmonate gastropods, and some arachnids. Their function is to conduct gas exchange by extracting oxygen from the air into the bloodstream via diffusion directly across the humidified airway epithelia, and to release carbon dioxide from the bloodstream out into the atmosphere, a process also known as respiration. This article primarily concerns with the lungs of tetrapods, which are paired and located on either side of the heart, occupying most of the volume of the thoracic cavity, and are homologous to the swim bladders in ray-finned fish.

<span class="mw-page-title-main">Gill</span> Respiratory organ used by aquatic organisms

A gill is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a large surface area to the external environment. Branchia is the zoologists' name for gills.

<span class="mw-page-title-main">Tetrapod</span> Superclass of the first four-limbed vertebrates and their descendants

A tetrapod is any four-limbed vertebrate animal of the superclass Tetrapoda. Tetrapods include all extant and extinct amphibians and amniotes, with the latter in turn evolving into two major clades, the sauropsids and synapsids. Some tetrapods, such as snakes, legless lizards, and caecilians, have evolved to become limbless via mutations of the Hox gene. Nevertheless, these limbless groups still qualify as tetrapods through their ancestry, and some retain a pair of vestigial spurs that are remnants of the hindlimbs.

<span class="mw-page-title-main">Respiratory system</span> Biological system in animals and plants for gas exchange

The respiratory system is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly, depending on the size of the organism, the environment in which it lives and its evolutionary history. In land animals, the respiratory surface is internalized as linings of the lungs. Gas exchange in the lungs occurs in millions of small air sacs; in mammals and reptiles, these are called alveoli, and in birds, they are known as atria. These microscopic air sacs have a very rich blood supply, thus bringing the air into close contact with the blood. These air sacs communicate with the external environment via a system of airways, or hollow tubes, of which the largest is the trachea, which branches in the middle of the chest into the two main bronchi. These enter the lungs where they branch into progressively narrower secondary and tertiary bronchi that branch into numerous smaller tubes, the bronchioles. In birds, the bronchioles are termed parabronchi. It is the bronchioles, or parabronchi that generally open into the microscopic alveoli in mammals and atria in birds. Air has to be pumped from the environment into the alveoli or atria by the process of breathing which involves the muscles of respiration.

<i>Amphiuma</i> Genus of amphibians

Amphiuma is a genus of aquatic salamanders from the United States, the only extant genus within the family Amphiumidae. They are colloquially known as amphiumas. They are also known to fishermen as "conger eels" or "Congo snakes", which are zoologically incorrect designations or misnomers, since amphiumas are actually salamanders, and not fish, nor reptiles and are not from Congo. Amphiuma exhibits one of the largest complements of DNA in the living world, around 25 times more than a human.

<span class="mw-page-title-main">Excretion</span> Elimination by an organism of metabolic waste products

Excretion is elimination of metabolic waste, which is an essential process in all organisms. In vertebrates, this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks after leaving the cell. For example, placental mammals expel urine from the bladder through the urethra, which is part of the excretory system. Unicellular organisms discharge waste products directly through the surface of the cell.

<span class="mw-page-title-main">Plethodontidae</span> Family of amphibians

Plethodontidae, or lungless salamanders, are a family of salamanders. With over 500 species, lungless salamanders are by far the largest family of salamanders in terms of their diversity. Most species are native to the Western Hemisphere, from British Columbia to Brazil. Only two extant genera occur in the Eastern Hemisphere: Speleomantes and Karsenia.

<span class="mw-page-title-main">Aquatic respiration</span> Process whereby an aquatic animal obtains oxygen from water

Aquatic respiration is the process whereby an aquatic organism exchanges respiratory gases with water, obtaining oxygen from oxygen dissolved in water and excreting carbon dioxide and some other metabolic waste products into the water.

<span class="mw-page-title-main">Gas exchange</span> Process by which gases diffuse through a biological membrane

Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.

In physiology, respiration is the movement of oxygen from the outside environment to the cells within tissues, and the removal of carbon dioxide in the opposite direction to the surrounding environment.

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<span class="mw-page-title-main">Amphibious fish</span> Fish that can leave water for periods of time

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<span class="mw-page-title-main">Nose</span> Organ that smells and facilitates breathing

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<span class="mw-page-title-main">Fish gill</span> Organ that allows fish to breathe underwater

Fish gills are organs that allow fish to breathe underwater. Most fish exchange gases like oxygen and carbon dioxide using gills that are protected under gill covers (operculum) on both sides of the pharynx (throat). Gills are tissues that are like short threads, protein structures called filaments. These filaments have many functions including the transfer of ions and water, as well as the exchange of oxygen, carbon dioxide, acids and ammonia. Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide.

<span class="mw-page-title-main">Fish physiology</span> Scientific study of how the component parts of fish function together in the living fish

Fish physiology is the scientific study of how the component parts of fish function together in the living fish. It can be contrasted with fish anatomy, which is the study of the form or morphology of fishes. In practice, fish anatomy and physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in the living fish.

Enteral respiration, also referred to as cloacal respiration or intestinal respiration, is a form of respiration in which gas exchange occurs across the epithelia of the enteral system, usually in the caudal cavity (cloaca). This is used in various species as an alternative respiration mechanism in hypoxic environments as a means to supplement blood oxygen.

References

  1. Tattersall, Glenn J. (2007), Aird, William C. (ed.), "Skin Breathing in Amphibians", Endothelial Biomedicine, Cambridge: Cambridge University Press, pp. 85–91, ISBN   978-0-521-85376-7 , retrieved 2021-03-16
  2. 1 2 3 4 5 6 Feder, Martin E.; Burggren, Warren W. (1985). "Cutaneous gas exchange in vertebrates: design, patterns, control and implications" (PDF). Biological Reviews. 60 (1): 1–45. doi:10.1111/j.1469-185X.1985.tb00416.x. PMID   3919777.
  3. Johnson, Peter H. Raven, George B. (2002). "Respiration". Biology (6th ed.). Boston: McGraw-Hill. pp.  1053-1070. ISBN   0073031208.{{cite book}}: CS1 maint: multiple names: authors list (link)
  4. 1 2 3 4 Kardong, Kenneth V. (2002). "The Respiratory System". Vertebrates: Comparative Anatomy, Function, Evolution (3rd ed.). Boston, MA: McGraw-Hill. p.  403. ISBN   0072909560.
  5. Skin structure in newborn marsupials with focus on cutaneous gas exchange