Tiny Zombie Worms Are the Beavers of the Deep

These deep-sea worms carve habitats out of whale bone.

Published May 15, 2017

Osedax worms, also known as zombie worms, have a taste for the macabre. After all, they eat bones. Specifically, whale bones that have sunk to the bottom of the sea. (Though they’ll also eat cow bones, if they happen to sink their way.) Resembling clusters of floppy, hot-pink feathers, these mouthless worms drill into skeletons, set down roots, and release acid that breaks down the bone so that they can absorb the luscious fat inside.

New research shows that this novel adaptation has effects that reverberate throughout the marine ecosystem. A recent study by a team led by Joan Alfaro-Lucas of Brazil’s University of São Paulo reveals that by boring into whale bones, Osedax worms create habitats for a wide array of species.

Alfaro-Lucas knows this because he spent a year sorting through the creatures found in the backbones of an Antarctic minke whale skeleton. The vertebrae—the only remains of the whale, which had fallen to a depth of over four kilometers off the coast of Rio de Janeiro—were collected by researchers using the submersible HOV Shinkai 6500.

In the lab, Alfaro-Lucas noticed that there was something strange about the whale vertebrae: four were more heavily pocked with holes than the other five. The more degraded bones were also embedded with Osedax, while those that were more intact were Osedax-free.

The team found that vertebrae that had Osedax worms living inside had three times as many colonizers as well, mainly roundworms and bristle worms. Osedax-filled vertebrae also contained twice as many total species, including rare ones that were absent from the other bones.

“We think that these holes and degraded areas can be used by other animals as a shelter, a place to feed on inner bone compounds, and an entrance to inner bone matrices,” says Alfaro-Lucas.

The findings suggest that Osedax are ecosystem engineers, creatures that create, transform, or destroy habitats—essentially, the Brahmas and Shivas of an ecosystem. It’s what beavers do when they dam streams, making ponds that attract more diverse birds and reptiles than the flowing streams did. Elephants do it, too, by digging pits, knocking down trees, and even creating shelter for the frogs that choose to call blobs of elephant dung home.

Part of what distinguishes the already peculiar Osedax worms is that the ecosystem they modify consists of sunken bones. According to Nicholas Higgs, deputy director of the Marine Institute at England’s Plymouth University, who was not involved in the study, whale skeletons resemble island habitats for the creatures that colonize them.

“They’re really interesting model animals for understanding dispersal in the deep ocean,” says Higgs. “Once whale skeletons are broken down by the Osedax, once they’re gone, those populations will die out and the only way they carry on is by their larvae drifting and finding another carcass.”

Hopefully, for them, Osedax will get there first.