Use of Concentration to Discover Why Camels Can Go Weeks Without Water

 

There are many reasons why camels can survive the desertís arid conditions:

  1. Instead of wasting water on disposing urea, their bodies recycle part of it. The nitrogen can be used to make amino acids, the building blocks of protein.
  2. Although they are warm-blooded, they still adjust their body temperature to the environment from about 37 to 40oC.
  3. Their fat is concentrated in their hump(s), so they have less insulation throughout the rest of the body. Contrary to popular belief, a camel does not store water in its hump(s) or anywhere else.
  4. Whereas the blood of most water-deprived mammals becomes thicker, leading to poor circulation and dangerously high body temperatures, a camelís blood vessels retain most of their water. How was this discovered?

 

In the 1950ís, Knut Schmidt-Nielsen and his wife injected a harmless dye in to a camelís bloodstream. They waited a while for the dye to distribute itself evenly. Then they took a blood sample and measured the concentration of the dye. Then the camel went 8 days without drinking in the desert heat. Although it lost a lot of weight (over 40 litres of water), the concentration of the dye in the blood revealed that the blood had only lost about 1 litre of water. In other words the rest of the water had been lost from tissues.

 

This is the kind of calculation that the Nielsens used:

 

Suppose that the original concentration of the dye had been 0.0495 g/L in 100 L* of blood. If the concentration of the dye had then increased to 0.0500 g/L, using C1V1 = C2V2,

0.0495(100) = 0.0500V2, would reveal V2 to be 99 L, a change of only 1 L.


*How did they know that the camel had a 100L of blood? Let's say they had originally injected 8.0 mL of 619 g/L of dye. After even distribution of the dye(before the camel went 8 days without drinking), the concentration became diluted to 0.0495 g/L, then C1V1 = C2V2,(0.0080) = 0.0495(0.008+V2), would reveal V2 to be about 100 L.

 

Reference:

 

Scientific American. The Physiology of the Camel. December, 1959.

Picture from George Holton, The National Audubon Society Collection/Photo Researchers