Blood Cells Protect From Dehydration

Biological Strategy

Dromedary camel

AskNature Team

Distribute Liquids

Liquids include water, as well as body fluids such as blood, gastric juices, nutrient-laden liquids, and more. To survive, many living systems must move such liquids within themselves or between locations. Because of their properties, liquids tend to disperse unless they are confined in some way. To address this, living systems have strategies to confine fluids for transport, and to overcome barriers such as gravity, friction, and other forces. Some of these same barriers also provide opportunities. Trees and giraffes face the same challenge: how to move fluids (water and blood, respectively) upward against gravity. But their strategies are quite different. The tree moves water using capillary action and evaporation, possibly due to water’s properties of polarity and adhesion. The giraffe’s tight skin provides pressure to assist in blood circulation. and keep blood from pooling in the legs.

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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 red blood cells of the dromedary camel protect it from dehydration because the oval-shaped cells can circulate even in thick blood and can significantly expand during rehydration.

The dromedary camel is incredibly well-adapted to hot, arid climates. The camel can go days without drinking water, surviving extreme dehydration and safely losing 40% of its body weight in water. This ability is, in part, due to uniquely oval red blood cells (which carry oxygen). The long axis of these oval cells is oriented with the flow of blood, enabling the cells to cross over the smallest of blood vessels, even when blood thickens during times of dehydration.

Additionally, the camel’s red blood cells are capable of expanding up to 240% of their original volume without rupturing; most animals’ cells can expand only 150%. This makes it possible for the camel to drink the necessarily large amount of water to recover from dehydration.

Last Updated September 14, 2016

References

“Camelid erythrocytes are small…and elipsoid^18,19,56,58 and circulate in larger numbers than in other mammalian species. The small size and shape result in a lower packed cell volume (PCV). Camelid erythrocytes are oriented with the long axis in the direction of the blood flow; this makes it possible to traverse small capillaries, resulting in fewer problems of sludging when the viscosity of the blood increases during dehydration.” (Fowler 2010:407,411)

“Even after severe dehydration, the camel is able to drink sufficient water at one session to make up the deficit. This amount of water would cause severe osmotic problems in humans or other animals. In the camel, water is absorbed from the stomach and intestines slowly, allowing equilibrium to be established. The erythrocytes are able to avoid osmotic problems by swelling to 240% of their initial volume without rupturing… In other species, erythrocytes can swell only to 150%…” (Fowler 2010:28)

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