Atlantic razor clams (Ensis directus) don't have the muscles to plow more than 1 or 2 cm into the sea floor. Yet somehow they're able to dig themselves 70 cm deep at up to a centimeter per second. The trick, new research reveals, is that the clams surround themselves with a pocket of quicksand. To make the discovery, researchers built a thin, rectangular tank and filled it with clear glass beads 1mm in diameter. They then placed the razor clams inside. When the animals contracted their shells, the surrounding "sediment" started to cave in. By pulling their shells in even closer, the clams drew surrounding water into the spaces between the beads. The resulting water-bead mixture reduced the resistance clams encountered while digging, researchers report online today in The Journal of Experimental Biology. Engineers are busy building small burrowing robots that mimic the clam's motions for use on autonomous underwater vehicles. The goal is to use them as anchors that dig themselves in and out of the sea floor, eliminating the need to use motors that would drain battery life while keeping the instrument stationary in the water.
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