Question

What is an adaptive feature of the nephron in a desert mammal, like a camel?

Answer 1

Camels have evolved to be able to survive in the desert. Large, flat feet - to disperse their weight on the sand - are one of their adaptations. The top of the body is covered in dense fur for shade, and the rest of the body is covered in thin fur to allow for simple heat dissipation. To maximise heat dissipation, a wide surface area to volume ratio is used.

Complete answer:
Camel nephrons have a well-developed Henle's loop, and the quantity of juxtamedullary nephrons in the kidneys is very high, about 35 percent (in man this number is about 15 percent ). Because desert mammals have a hard time finding water, they must excrete a small amount of water. They have the ability to create urine that is extremely concentrated.

The Henle's loop of juxtamedullary (=adjacent to the medulla of the kidney) nephron extends deep into the medulla, as seen in the accompanying diagram. This explains why the medulla of a camel's kidney is thicker than that of other mammals, but it is best developed in kangaroo rats, another desert species.

Water conservation is aided by Henle's loops of juxtamedullary nephrons and counterflowing blood arteries, known as vasa recta.

Blood travels up the ascending limb of Henle, which is water-resistant. Along this stretch, solutes can leave the filtrate and enter the bloodstream. Water from the filtrate is reabsorbed along the descending limb, but not the solutes. The longer Henle's loop, the more solute will be reabsorbed, and hence more water will be eliminated from the filtrate.

Camels have large feet that make it easier for them to move on the sand. Their enormous feet allow them to walk on sand without sinking. Camels have broad lips, which allows them to chew prickly desert plants without pain.

Note: The camel has a unique kidney and gastrointestinal tract. The kidney of a camel can concentrate urine more than seawater, but less than that of a desert rat. Because the camel's pee can concentrate more than seawater, salty water will not injure the animal.