Cutaneous respiration

Cutaneous respiration, or cutaneous gas exchange, 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, excluding humans.

Gas exchange in cutaneous respiration is controlled by three factors:

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.

The skin of amphibians is a major site of respiration in all species for which measurements are available. 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.

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. Cutaneous respiration in hellbenders accounts for more than 90 percent of oxygen uptake and carbon dioxide excretion.

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