​Drifting acorn worm with externalized ovaries: Allapasus aurianticus observed by the remotely operated vehicle Tiburon drifting in a deep-sea current just inches off the sea floor at 3000 m. For more info see: Journal of Morphology. Morphology of a New Deep-Sea Acorn Worm (Class Enteropneusta, Phylum Hemichordata): A Part-Time Demersal Drifter with Externalized Ovaries
Nicholas D. Holland, Linda A. Kuhnz, and Karen J. Osborn

Photograph courtesy David Shale

Sporting a bright fuchsia hue, this new species of acorn worm was recently found some 8,850 feet (2,700 meters) deep near the Mid-Atlantic Ridge. The colorful creature is one of more than 12 new species and at least 4 new genera of worms discovered during two recent deep-sea expeditions, scientists have confirmed.

The research has shed new light on acorn worms, formerly known as a homogeneous group called shallow-water burrowers, said Karen Osborn, an evolutionary biologist at the Smithsonian Institution's National Museum of Natural History in Washington, D.C.

"The shallow-water worms pretty much all look the same," said Osborn, who co-authored a new study—published November 16 in Proceedings of the Royal Society B—showing the worms live in deep waters worldwide.

"But at some point, one of these shallow-water guys got into deep water, and they've changed their morphology to deal with the unique challenges of that deep-sea habitat."

For instance, the deepwater worms have extremely long "lips" that help them snag prey in a place where food is scarce.

"So now we have this group of deep-sea species that look[s] totally different and behave[s] differently [than the shallow-water worms]—leaving their burrows behind."