It’s bright orange and yellow and about as long as your finger. It lives underwater in a limestone tube with an opening at the tip about as wide as a pencil eraser. It glues its home to hard surfaces and stays for the rest of its life. It’s a species of worm-snail that may never have been seen before, and somehow it turned up in an artificial reef in the Florida Keys.
On land, its table manners would not seem so polite. It shoots strings of mucus from its mantle — a footlike appendage hanging out of the tube’s opening — in slow motion, like some warped, weirdo, saltwater version of Spider-Man. It releases the strings into the current, forming a snotty web that it holds on to with its equivalent of a toothy tongue, trapping plankton and other ocean debris. Then it reels in whatever it has trapped, along with the snot.
In a study published Wednesday in PeerJ, scientists have identified this new species of worm-snail. They’ve named it Thylacodes vandyensis after the General Hoyt S. Vandenburg, a sunken, retired naval ship where tens of thousands of the snails live. If they spread elsewhere, the worm-snails could damage the region’s living coral.
The Vandy, as divers have nicknamed it, is among a number of large, retired ships sunk in the Florida Keys National Marine Sanctuary to provide new homes for ocean creatures and alternative diving spots.
Researchers like Rüdiger Bieler, a curator at the Field Museum in Chicago and the lead author of the paper, monitor these artificial reefs to see what’s settling in. In 2014, during two 20-minute dives, he and his colleagues found three of these worm-snails. Now there are thousands.
Dr. Bieler thinks the worm-snails could indicate what kind of marine life is settling into the reefs. To make a terrestrial comparison: “Are we getting the native butterflies back, or are we just seeing feral cats?” he wonders. “It’s a new species, but we’re still not 100 percent sure where it’s coming from.”
The closest relatives of the previously undescribed worm-snails are native to the Pacific Ocean. He speculates that these mollusks stowed away on a ship before taking advantage of the uninhabited artificial reefs: “There’s this brand-new real estate where there are nonlocal species, few predators and very little competition.”
Monitoring these creatures on the Vandy could help prevent their spread to natural reefs, where they could do great damage. Similar worm-snails found in the Pacific and the Red Sea have been found to slow coral reef recovery by killing coral tissue and chasing off fish with a bioactive compound in their mucus.
“When you have them in the living reef,” Dr. Bieler said, “there’s always this kind of death zone around them.”