These curious creatures were first discovered in the Arabian Sea thirteen years ago. Recently, scientists with NOAA have discovered the same creatures in deep sea Little San Salvador, Bahamas, near where I learned to dive last year.
The “Bahamian Gromia,” as these single-celled organisms have come to be called, are special because of their mechanism of movement. They slowly, almost imperceptibly, roll themselves along the sea floor. Duke biology professor, Sönke Johnsen, speculated that the gromia does, indeed, self-propel, but was unable to determine how.
Johnsen noted, “We watched the video over and over, 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.”
The controversy over these animals is due to a discrepancy in the fossil record. The trail left by the gromia as they roll around matches recorded fossilized mud tracks. Scientists who examined these fossils, which predate the “Cambrian Explosion” when multi-cellular organisms began to emerge, believed that multi-cellular organism must have come into existence earlier because the tracks could not have been made by uni-cellular organisms. The gromia prove this notion false.
The gromia can be likened to a “thick balloon,” with most cell organelles close to the surface and a liquid-filled center. Most likely, the gromia take in sediment and symbiotic bacteria decompose their food for them. Little else is known about these creatures because attempts at a captive study have failed due to their frailty.