Cutaneous respiration, orcutaneous gas exchange (sometimes calledskinbreathing),[1] is a form ofrespiration in whichgas exchange occurs across theskin or outerintegument of an organism rather thangills orlungs. Cutaneous respiration may be the sole method of gas exchange, or may accompany other forms, such asventilation. Cutaneous respiration occurs in a wide variety of organisms, includinginsects,amphibians,fish,sea snakes,turtles, and to a lesser extent inmammals.
Gas exchange in cutaneous respiration is controlled by three factors:[2]
Cutaneous respiration occurs in a variety of marine, intertidal, and freshwater fish. Foraquatic respiration, fish respire primarily viagills 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 asmudskippers andreedfish, and in such species may account for almost 50 percent of total respiration.[2]
The skin ofamphibians is a major site of respiration in all species for which measurements are available.[2] Cutaneous respiration is the sole respiratory mode oflungless 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 thehellbender salamander and theLake Titicaca water frog.[2] Cutaneous respiration in hellbenders accounts for more than 90 percent of oxygen uptake and carbon dioxide excretion.[4]
Being covered inscales largely precludes cutaneous respiration in reptiles, but gas exchange may occur between scales or areas with reduced scales. Some turtles rely on cutaneous respiration fromenteral respiration around thecloaca during underwater hibernation.[4]
In somesea 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 areendotherms, ("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 theJulia Creek dunnart the newborns are extremely small, and 95% of their gas exchange happens via their skin.[5]
{{citation}}: CS1 maint: work parameter with ISBN (link){{cite book}}: CS1 maint: multiple names: authors list (link)