Skin Protects From Dehydration

Biological Strategy

Granulated file snake

AskNature Team

Image: David Clode / Unsplash / Free non-commercial use

Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

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Protect From Loss of Liquids

Water is essential to life. Liquids, mostly water, make up 70 to 90% of all living systems, and the loss of even a small percentage can mean the difference between life and death. Living systems must maintain a proper liquid balance, which is especially difficult in dry conditions. To do so, they must control the movement of liquids across their boundaries. Living systems do this using structures or waterproof materials to prevent or slow liquid movement. For example, when humans receive a cut, they must limit blood loss. Scattered throughout the bloodstream are lens-shaped structures that serve to plug the wound.

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Reptiles

Class Reptilia (“creeping”): Lizards, crocodiles, turtles, snakes

Reptiles retain some of the key characteristics that first enabled vertebrates to live permanently on land. They have dry skin covered in scales made of keratin that help prevent water loss. (Amphibians still need to stick close to water to keep their skin moist.) Many reptiles reproduce by laying eggs that are watertight and have a yolk, so eggs can develop on land while staying moist and nourished. Reptiles are also ectotherms, meaning they don’t produce their own body heat. This means they burn through energy much more slowly than “warm blooded” creatures of the same size. It also means that they need to keep warm to keep active, which is why you might see them spending a seemingly inordinate amount of time simply basking in the sun.

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The skin of file snakes protects from dehydration because it is hygroscopic, absorbing moisture from the air.

Image: Nelly de Rooij / Wikimedia Commons /

Chersydrus granulatus

“The granular skin of Acrochordus is hygroscopic and imbibes water which moves rapidly over the body surface through interscalar channels. Consequently, the integument is easily wetted to bear a superficial aqueous film = 5.4 mg water per cm² of skin surface. Although file snakes are aquatic, they can become entrapped in drying ephemeral pools and have been observed on tidal mud flats where they are potentially exposed to intense heat and dehydration. Superficial water films, therefore, have a potentially important biological role in reducing dehydration of skin or body while extending the time available for terrestrial sojourns between areas of water.” (Lillywhite and Sanmartino 1993:99)

Last Updated September 14, 2016

References

Journal article

Permeability and Water Relations of Hygroscopic Skin of the File Snake, Acrochordus granulatus

Copeia | 26/04/2006 | Harvey B. Lillywhite, Veronica Sanmartino

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