Giant, single-celled sea creatures confound by rolling across the ocean floor:The grape-like animal, tentatively named the Bahamian Gromia, is actually a single-celled organism, fully one inch long. But what makes it really fantastic is that it moves -- very slowly -- by rolling itself along the ocean floor...."We watched the video over and over," Johnsen said. The trails couldn't be the result of currents because they went in several directions at the same spot, and sometimes they even changed course. And they weren't the result of rolling downhill. In fact, one trail was found that went down into a small depression and came back up the other side.
"We argued about it forever," Johnsen said. "These things can't possibly be moving!" But they are, at a rate too slow to be captured on the sub's video. Johnsen guesses they move maybe an inch a day or less.
The distinctive trail that the Gromias leave is identical to mud tracks found in the fossil record, which throws a big wrench into one long-standing argument in biology. The fossil tracks pre-date the so-called "Cambrian explosion" 530 million years ago, which was a blossoming of multicellular life and complex body plans from what had previously just been simple, blobby life forms. Many paleontologists and evolutionary biologists have argued that such a trail couldn't possibly have been made by a simple organism, meaning complex body plans were around before the Cambrian explosion. But the Gromia show that simple blobs can indeed move and make tracks in the light, silty bottom.
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