A video has caught an underwater animal, which looks like a flower, practically jogging along the ocean bottom.
The stalked crinoid spends most of its time sitting and catching food with the flowerlike wheel of feathery arms that have earned it and its relatives the nickname sea lilies. Scientists had known for decades that stalked crinoids sometimes move—but barely. They had been clocked at speeds no greater than 0.6 meter per hour.
Now, however, a video from a submersible dive off Grand Bahama Island reveals a speed demon, says Tomasz Baumiller of the University of Michigan in Ann Arbor.
A stalked crinoid pulled itself along the bottom briskly enough for a viewer to notice. Baumiller and Charles Messing of Nova Southeastern University’s Oceanographic Center in Dania Beach, Fla., measured its pace at 140 m per hour. Baumiller presented the video in Salt Lake City on Oct. 16 at the annual meeting of the Geological Society of America. (To view the video, click here.)
“People were speechless,” says William I. Ausich of Ohio State University in Columbus. “It adds a whole new dynamic to understanding a very important group of animals.”
Crinoids, which are relatives of starfish and sea urchins, once had achieved such abundance and diversity that paleontologists refer to the period 350 million years ago as the age of crinoids. Today, only two main forms remain.
Two decades ago, Baumiller and Messing independently documented movement by some stalked crinoids. Baumiller observed creeping stalks in a lab. Messing, among other observations, dove in a submersible to plot positions of individual crinoids in an ocean-bottom garden and returned months later to find that they had shifted.
“The movement was so slow that no one got terribly excited,” says Baumiller.
The researchers suspected that crinoids flee from hungry sea urchins. So, Baumiller and Messing joined forces with an urchin specialist, Richard Mooi of the California Academy of Sciences in San Francisco.
Looking through hundreds of hours of archived video documentation of submersible dives from the 1990s, the researchers found the sprinting crinoid at a depth of about 400 m. In the video, it lies on the bottom and pulls itself along with its arms, “like a soldier’s elbow crawl,” says Baumiller.
Carlton Brett of the University of Cincinnati describes the locomotion as “knuckle walking.” He says that the speed was indeed a surprise, but that it fits into emerging scenarios suggesting that competition between crinoids and their predators influences each creature’s evolution.
