The digging motions of a razor clam.
The soft, pale foot of a six-inch long razor clam burrows through sand at an impressive rate of four body lengths per minute (video). When scientists put muscles in the razor clam to the strength test though, they found that its foot was only 1/10 as strong as it would need to be to dig so fast. What gives? The sand, literally.
Instead of relying on brute force, the burrowing razor clam turns the sediment around itself into quicksand, according to a study published in the Journal of Experimental Biology. And as Hollywood has taught us well, it’s easy to sink in quicksand.* The razor clam pulls its shell up, creating a vacuum that sucks water into the space surrounding its body. Quicksand is just sand with enough water between all its particles so that it no longer holds any weight, making it easy for the razor clam to tunnel down. Although most (big) pools of quicksand are created by earthquakes or flowing water, the razor clam’s small scale strategy is quite effective. In fact, the little buggers are so fast that recreational clam digging actually takes some practice.
*The human body is actually too buoyant to sink beyond the armpits in quicksand. So no, you can’t die of drowning in quicksand but you can get stuck and die of dehydration. Comforting thought, right?
Image via Winter et al. / J. Experimental Bio
Sandfish lizards jostle back and forth, bending their bodies into a slithery S-curve to swim through the sands of the Sahara. Like scorpions and several other native desert species, they long ago mastered the difficult art of moving through the myriad grains of a sandy expanse to escape predators or the blistering African sun. And now physicists are close to cracking their secrets.
Daniel Goldman’s team has been trying to figure out just how the sandfish lizards do it for years now; in 2009 they built a robot to simulate the creature’s slithering motion. This time, for a study in the Journal of the Royal Society Interface, the scientists tried to model the physics of an animal knocking around so many grains of sand and see how the lizards burrow with such efficiency.
The team found sine-wave-like movement allows the lizard, and their robot, to push forward in sand, but creating computer models for the experiments proved problematic. Simulating all of the tiny sand grains required a lot of money to purchase time on powerful computers. So, the team performed the same experiments using 3-millimeter-wide glass beads instead of sand. “We wanted something easy to simulate that had some predictive power. We got lucky, because it turned out [the lizard and robot] swim beautifully in the same way through larger glass beads,” Goldman said. [Wired]