New Species of Naked Bone-Eating Worms in Antarctica

Eating at Home

Photograph courtesy Deep Slope Expedition 2006, NOAA/OE  

Whale falls such as this one, pictured off the California coast in 2004, make for tempting living conditions if you're a bone-eating worm.

They colonize the skeleton, dig deep with "roots" to suck up nutrients, and even reproduce amidst the wreckage. (Related: "'Zombie' Worms Mate Inside Whale Bones.")

It's possible that dolphin or seal carcasses could also host Osedax worms, said study co-author Dahlgren. "[But] no one has seen them on naturally occurring bones of groups other than [whales]." (Related: "Dead Whale Contains a Bounty of Life.")

Dolphin or seal bones are smaller than whale bones, he added, so they are more readily disturbed or dispersed than big whale carcasses are. That could affect whether Osedax species would colonize them.

But Dahlgren and another researcher, Robert Vrijenhoek of the Monterey Bay Aquarium Research Institute, have set out cow bones as experiments to see if the worms would settle on them—they did.

"So yes, they can definitely inhabit or use other types of bones," Dahlgren said. "But we are not sure about the extent of that in nature."

Published August 13, 2013

Field of Worms

Photograph courtesy Thomas Dahlgren  

Several individuals of a new species of bone-eating worm, Osedax antarcticus, stick up from a whale bone researchers left on the seafloor off the coast of the West Antarctic shelf.

Bone-eating worms have been found only in the oceans surrounding Japan, California, Scandinavia, and now the Antarctic, said Uni Research's Dahlgren. But it's possible that wherever you find whale falls, you'll also find bone-eating worms.

Published August 13, 2013

Where Are the Worms?

Photograph courtesy Thomas Dahlgren  

In addition to laying out whale bones on the seafloor to see what colonized them, the researchers also placed pieces of wood to see what made a home there.

Shipworms—which are actually mollusks—are the bane of many a mariner's existence. The organisms bore into the wood of ships and other wooden structures, like piers, destroying them in the process. (Related: "Viking Shipwrecks Face Ruin as Odd 'Worms' Invade.")

Shipworm larvae behave a little like bone-eating worm larvae in that both need to colonize habitats that are only around temporarily, and that can be hundreds of miles or kilometers apart, the study authors write.

But when the researchers set out pieces of wood along with the whale bones, they found a complete absence of shipworms. "We kind of expected them to be there," said Dahlgren.

Instead, hydroids (pictured), which are related to corals and jellyfish, settled on the planks.

Dahlgren and colleagues speculate that perhaps circulation patterns prevent shipworms from other parts of the world from colonizing the ocean around Antarctica.

Published August 13, 2013

'Naked' Worms

Photograph courtesy Thomas Dahlgren  

The palps (pictured) on Osedax antarcticus—which function like lungs in gas exchange—lack the extensions seen on other Osedax species. Researchers call these "naked" palps, and both new species sport them.

"It's a little bit too early to speculate on the ecological meaning of this, but that's an important find," said Dahlgren.

Other Osedax species have naked palps, but there doesn't seem to be any other commonality, either in terms of depth or geography, between them.

Published August 13, 2013

Close-Up

Image courtesy Adrian Glover  

A high-resolution electron micrograph of Osedax antarcticus allows researchers to study all the nooks and crannies of this new species, from the palps (upper left) to the rest of the body.

The second newfound species, O. deceptionensis, was found in only 69 feet (21 meters) of water, surprising the researchers.

"[This] is quite astonishing because the Osedaxes we know are deep-sea," said Dahlgren.

This finding expands the depth range for bone-eating worms from about 9,400 feet (2,800 meters) to 69 feet (21 meters).

Published August 13, 2013

Jaws

Image courtesy Adrian Glover  

A high-resolution electron micrograph shows details of the jaws on a male Osedax antarcticus. These jaws alert researchers to the fact that the new species are in fact related to polycheate worms—which are related to a group that includes earthworms.

But the new Antarctic finds have reworked this family tree. Previous studies, one of which was co-authored by Dahlgren, showed the bone-eating worms as more closely related to the group of worms that live at hydrothermal vents.

With a larger genetic sample—made possible by the discovery of these two new species—it now looks like bone-eating worms are more closely related to a group of mud-dwelling worms called frenulates, Dahlgren said.

These thread-like worms are fairly common, he said, but not much is known about them. "They're extremely thin, so as soon as you try to dissect one, it breaks," he said. "So it's a big challenge to study them."

Published August 13, 2013

Send in the Males

Photograph courtesy Thomas Dahlgren  

Male bone-eating worms are much smaller than females. The males of some species—two Osedax antarcticus are pictured here crawling on the trunk of a female—are so small that they can live inside the female, acting as sperm donors.

Published August 13, 2013

See Previous Bone-Eating Worm Discoveries

Photograph courtesy Greg Rouse, MBARI

Published August 13, 2013