The sandfish lizard spends most of its life buried in the sand—emerging only to eat, poop, and make love. This lifestyle helps the lizard evade the sweltering desert heat in the Middle East and North Africa, but it causes another problem: inhaling sand particles. Yet when scientists looked into the respiratory tract and lungs of five dead lizards, they couldn’t find a single grain of sand. They couldn’t find an obvious filter in the lizard’s respiratory system, either. Puzzled, the scientists attached sensors to the chests of living lizards and studied their breathing patterns. They found the lizards breathe out with about 60% more intensity inside their sandy burrows than when they are aboveground, which might allow them to expel sand particles from their nostrils. The scientists also estimated a 70% drop in the speed of inhaled air when it hits the widest section of the lizard’s respiratory tract. This likely means that as the air slows down, sand particles fall and get trapped in mucus and cilia that line the section, the scientists report today in the Journal of Experimental Biology. From there, some particles are blown out during exhalation and others are swallowed, after which they pass through the digestive tract and out of the body. At least, that’s the latest theory, supported by the fact that the lizards’ guts were full of sand.
Read our COVID-19 research and news.