The next time you walk barefoot on the beach, and let the wet sand squish between your toes, think about this: You might be walking through the homes of thousands of tiny creatures.
These aren’t the little crabs that we see scuttling in and out of their burrows, though -- they’re even smaller: snails, worms, and other organisms that are smaller than the head of a pin.
These creatures live just below the surface, between the grains of sand. This environment stays damp even when the tide is out. It also provides protection from the summer Sun, and it maintains a fairly constant salinity. All in all, a comfortable home for a tiny creature.
And plenty of them take advantage. One study on an Arctic island found as many as a million of them in the top inch of a patch of beach about the size of a kitchen table. And another found about five million in the same volume of a Texas beach.
Biologists have identified more than a thousand species that live in this environment, and hundreds more may await discovery. Many of them are types of worms -- flat ribbons, “hairy” tubes, or little curlicues. Others are crustaceans that look like shrimp or little armored tanks. Many of them are food for larger crabs and fish.
One of the oddest of the sand dwellers is the water bear. Its plump body has four pairs of legs, each with four to eight sets of claws. If a water bear dries out or undergoes other stresses, it curls up and goes into a near-death state. It can survive for years.
Copyright 2007, The University of Texas Marine Science Institute