The African elephant is known for its thick, wrinkled skin. But look closer, and you'll see a complicated network of tiny crevices that remind the skin of the mighty mammal of cracked mud or damaged asphalt.
The purpose of these cracks is no secret. An elephant has no sweat or sebaceous glands, so it covers its skin in water or mud to stay cool. The micrometer-wide cracks in his skin save 10 times more moisture than a flat surface and help the animal regulate its body temperature. They also help mud cling to the skin, which protects against parasites and sun rays.
Now, a team of researchers believe that they have discovered that these cracks bend as a result of stress on the skin, do not shrink. Their statement, published in Nature Communications on Tuesday, may even include clues to the treatment of a common human genetic skin disorder.
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Michel Milinkovitch, an evolutionary biologist at the University of Geneva in Switzerland, knows a little about crackling animal skin. In 201
This idea got a boost when Dr. Milinkovitch's team examined elephant skin samples under a microscope. They found that just under the thick top layer was a bottom layer of papillae, the same kind of small prominences found on the human tongue. These projections form a huge screen of prickly peaks and valleys. This seemed to support their assumption about the formation of the cracks.
"We thought," Oh, it's a simple story, "he said. "If we shrink something that is bound to such a geometry, the cracks will appear in the lower valleys."
But when they did computer simulations of the growing elephant skin, they found that the skin did not rupture as they had expected. Shrinkage alone would not explain the skin pattern of an elephant.
Further examination of the skin tissue revealed that dead skin cells from elephants resemble those of people who suffer from ichthyosis vulgaris, a disease that occurs in every 250 people and prevents the onset of skin. In humans, the condition for which there is no cure causes thick, dry dandruff on the surface of the skin that is normally treated with moisturizers.
But for African elephants, sticking to this dead skin seems to be beneficial: The lack of hair loss causes the skin to build up as the elephant ages, eventually bending over the optic disc and breaking, giving the animal the opportunity to stay cool.
"When the skin peels off, it never becomes thick enough to create tension in the small valleys of this elevation lattice, and the tears would not develop," Dr. Milinkovitch. "In humans, that's not a helpful problem."
Further research is needed to determine if the lack of skin excretion in elephants has a genetic basis with human ichthyosis vulgaris. But the confluence of conditions could suggest a way forward for the treatment of the disease.