Sand bubbler crabs (or sand-bubblers) are crabs of the genera Scopimera and Dotilla in the family Dotillidae. They are s…

Sand bubbler crabs (or sand-bubblers) are crabs of the genera Scopimera and Dotilla in the family Dotillidae. They are small crabs that live on sandy beaches in the tropical Indo-Pacific. They feed by filtering sand through their mouthparts, leaving behind balls of sand that are disintegrated by the incoming high tide.

Basically, the tiny balls are a byproduct of the crabs' snacking. They don't eat the sand, but they do feed it through the bottom of an adapted mouth of sorts, filtering out all of the micronutrients that the high tide has brought in and dumped on the beach since their last feeding session.

In each burrow, the crab waits out the high tide in a bubble of air.

- @science -