In the late 1980s the researchers observed that sea lilies could, in fact, move from place to place---Baumiller had put some in a flow tank and noticed that they changed position from day to day, and Messing had noticed the same thing during dives with a submersible off Jamaica and Grand Cayman Island. Both researchers saw sea lilies using their feathery arms to crawl, dragging their stalks behind them, but the scientists wondered what induced sea lilies to relocate in nature. Physical disturbance, overcrowding or predation all were possible factors, but compelling evidence for any of these explanations was lacking.
Then, while going through hundreds of hours of video shot during submersible dives made more than a decade ago, the researchers came across footage that offered an explanation for why sea lilies might get up and go. The videos showed sea urchins lurking in gardens of sea lilies, some of which appeared to be crawling away from the predators. In some photos, the sea floor around the urchins was littered with sea lily appendages, like table scraps left from a feast. What's more, the sea lilies were moving a hundred times faster than previous observations had suggested.
Further studies by Baumiller, Messing, and Rich Mooi of the California Academy of Sciences suggested that sea urchins don't eat bits of dead sea lilies that they find on the ocean floor but rather bite pieces right off their prey, giving sea lilies plenty of incentive to shed their stalk ends and flee.
"It's the lizard's tail strategy," said Baumiller, who is also a curator in the UM Museum of Paleontology. "The sea lily just leaves the stalk end behind. The sea urchin is preoccupied going after that, and the sea lily crawls away." And the speed at which they move---three to four centimeters per second---suggests that "in a race with a sea urchin, the sea l
Source:University of Michigan