It's a flower? It's a jellyfish? It's a mushroom? No, it's a worm!
Not the wriggly, dirt-loving variety, but a delicate, gelatinous denizen of the deep sea, where 85 percent of life is still unknown to science—long the case for this frilly pink-and-yellow member of the acorn worm genus Torquaratoridae.
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Before 2005 only two species of acorn worm from the deep sea had ever been described. Now an international group of scientists led by Karen Osborn, an associate curator at the Smithsonian Institution, has turned up at least nine new species thriving in the Pacific and Atlantic oceans.
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Deep-sea acorn worms evolved from their much better known shallow-water cousins, which spend their lives more the way one might expect from a worm: burrowed in the mud and sand. The gelatinous bodies of the deep-sea worms are acutely lacking the strong muscles of their burrowing ancestors.
That adaptation made perfect sense once the researchers realized they're not hoisting mud and sand all day. These critters live on the sediment, not in it, leaving telltale trails in the soft mud as they feed (below, left).
What Osborn and her colleagues find particularly fascinating is the way deep-sea acorn worms get around. When they grow tired of one feeding ground, they don't crawl across the seafloor or tunnel through it. Instead, they hitch a ride on deep-sea currents.
In video captured by remotely operated vehicles (ROVs), Osborn and her colleagues have watched the worms make lift off by contorting or curling their bodies and by producing a mucus balloon. To sink back to the bottom, the worms release ballast (either mucus or poop) or simply straighten out their bodies (above, right).
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Since 2000 Osborn and her colleagues have made nearly 500 observations of of deep-sea acorn worms, shooting video and grabbing samples whenever they could, wherever the ROVs happened to be (usually studying geological features such as hydrothermal vents or volcanic ridges).
“So much remains to be learned about the deep oceans, yet we are changing this largest of earth’s habitats faster than we are studying it,” Osborn told Discovery News. “The diversity discovered here is only the 'tip of the iceberg' for deep-sea acorn worms."
IMAGES:
Deep-sea acorn worm Torquaratoridae. (Courtesy David Shale)
A second species of Torquaratoridae uncurls from its coiled drifting posture into the straight sinking posture (Courtesy MBARI Tiburon)
Deep-sea acorn worm Tergivelum clears a spiral track as it feeds on the soft upper layer of the seafloor sediment. (Courtesy David Shale)
A third species Torquaratoridae. (Courtesy David Shale)
Tags: Animal Behavior, Biodiversity, Oceanography, Zoology
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