Nasal Turbinates Reduce Water Loss

two northern elephant seals with prominent noses bark near the ocean in california

Biological Strategy

Northern elephant seal

AskNature Team

Image: Mike Baird / Wikimedia Commons / CC BY - Creative Commons Attribution alone

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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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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The nasal turbinates of the northern elephant seal reduce water loss via countercurrent heat exchange.

During the breeding season northern elephant seal males go without food and water for three months and weaned pups may fast for 2-3 months. Their only source of water is that produced by metabolizing their fat stores. Therefore, like animals in arid environments, they must conserve water by minimizing water loss.

Respiration can be a significant cause of water loss. Species like the elephant seal, penguin, reindeer, camel, kangaroo rat have a particularly effective so-called temporal counter-current exchange mechanism in their nasal passages that minimizes the amount of water lost from the respiratory system. The nasal turbinates are important structural and functional components of this mechanism. This is a series of boney, shelf-like structures in the nasal passageway covered with a well-vascularized layer of moist tissue and mucus. Inhaled air passing over this surface is warmed and moistened, and the surfaces cool due to evaporation. When the animal exhales, warm, water-saturated air from the lungs passes across the cooled nasal turbinate surfaces and water condenses out of it, staying within the nasal passages rather than being lost to the outside air. Those species with the highest percentage respiratory water recovery (e.g., 92% in the elephant seal compared to 24% in the sheep), have the most complex nasal turbinate structure. The key features of the more elaborate nasal turbinates are their very large surface area and the short distance from that surface to the middle of the airstream.

Designs of nasal turbinates in marine mammals like the elephant seal may offer inspiration for the design of more effective human-constructed water and heat recapturing systems.

Image: Mike Baird /

Last Updated February 13, 2018

References

“Elephant seals fast completely from food and water for 1-3 months during terrestrial breeding. Temporal countercurrent heat exchange in the nasal passage reduces expired air temperature (Te) below body temperature (Tb). At a mean ambient temperature of 13.7 degrees C, Te is 20.9 degrees C. This results in the recovery of 71.5% of the water added to inspired air. The amount of cooling of the expired air (Tb – Te) and the percentage of water recovery varies inversely with ambient temperature. Total nasal surface area available for heat and water exchange, located in the highly convoluted nasal turbinates, is estimated to be 720 cm² in weaned pups and 3140 cm² in an adult male. Nasal temporal countercurrent heat exchange reduces total water loss sufficiently to allow maintenance of water balance using metabolic water production alone.” (Huntley et al. 1984:447)

Journal article

The contribution of nasal countercurrent heat exchange to water balance in the northern elephant seal, Mirounga angustirostris

Journal of Experimental Biology, 113: 447-454 | 01/11/1984 | A. C. Huntley, D. P. Costa, R. D. Rubin

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Reference

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