Animal aqueduct

Natural History, Nov, 2007 by Stephan Reebs

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Cuddly they're not, but the Texas horned lizard and the Australian thorny devil share more than just prickles. They boast the same remarkable adaptation to their arid homelands: scale-covered skin that captures water and carries it to the animal's mouth, enabling it to drink when raindrops hit its back or even, in the thorny devil's case, when its belly meets damp sand. Recently, a team led by Wade C. Sherbrooke of the American Museum of Natural History in New York figured out how this weird plumbing system works.

Using advanced microscopy, the investigators discovered minute ducts beneath the base of the skin scales. The hair-fine ducts connect to form a network that covers the lizard's body and opens up in the corner of the mouth. Sherbrooke and his colleagues think that water, pulled by capillary action, slips under the scales and spreads through the interconnected ducts. The animal, apparently by moving its tongue and jaws in a particular way, can draw the water into its mouth and take a sip.

As their names suggest, the Australian thorny devil and the Texas horned lizard live on opposite sides of the world and are not closely related, and so the water-transporting skin that cloaks both species is a striking example of convergent evolution. (Zoomorphology)

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