There’s plenty of air in the tiny spaces between grains of sand; the problem for sand-burrowing animals is how to get that air into their lungs while keeping the sand out.
Narrow nostrils help, but other clever adaptations are also needed. The Colorado Desert fringe-toed lizard, for instance, is equipped with a respiratory U-bend that traps sand before it can reach the lungs, while the sandfish, a burrowing skink from North Africa and the Middle East, has a particularly wide section of respiratory tract.
This slows down the stream of inhaled air, allowing any sand particles to fall onto a layer of sticky mucous, which is then coughed up, keeping the lungs entirely sand-free.
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