Whale-Eaters Surprise Scientists

-A member of a species likely new to science, the Osedax yellow-collared worm feasts on whale bones in 2008. Named for the thin yellow ring that runs around the base of the worm's feathery structures--thought to be used for respiration--the species lives below 3,280 feet (1,000 meters).

The first known Osedax worms, which tend to feed on whale remains, were first scientifically described in 2004. A short five years later, new types of the bone-eating worms are turning up as fast as scientists can study them. (See "New Worms Eat (and Eat and Eat) Only on Dead Whales.")

So far, scientists have confirmed five Osedax species, which live between 82 feet to 9,842 feet (25 to 3,000 meters) deep in the Pacific and Atlantic Oceans. And in November researchers from the Monterey Bay Aquarium Research Institute revealed evidence of 12 more potentially new species, including the yellow-collar, all found in the undersea canyon off Monterey, California.


All the potential new bone-eating worms announced in November by Monterey Bay scientists were found on whale carcasses the scientists dragged out to sea. Whale bones, like this skull pictured 1.1 miles (1,800 meters) underwater in 2006, present a remarkable feeding opportunity for bone-eating worms, but the feast isn't for everyone.

While female worms can readily attach to the bone and begin feeding, male worms are too small to do so. Instead, they tend to dwell inside gelatinous tubes surrounding the bodies of females and do little more than produce sperm.



At roughly two millimeters long, the bone-eating worm species pictured above in 2009, is among the smallest known.

The minuscule Osedax variety, which has yet to be formally named, has "probably been overlooked in the past because they are nearly invisible," said marine biologist Robert Vrijenhoek, who led the Monterey Bay Aquarium Research Institute study. The worms' bodies are transparent and lack the showy, feathery, plumes that make many of their bone-eating kin comparatively easy to spot.



An Osedax orange-collar worm--another of the potential new species announced in November 2009--releases barely visible, speck-like eggs in Monterey Canyon in 2008.

"We are really lucky at the Monterey Bay Aquarium Research Institute to have robotic submarines equipped with high-definition cameras that can capture images like this at 1,000 meters [0.6 mile] depth," study leader Vrijenhoek said.



The newfound undersea worms--such as this still-unnamed variety pictured after it had been separated from its bone perch for study in 2009--likely eat by absorbing bone nutrients through their bulbous roots.

"They have no anus, no mouth, no digestive tract that we can detect, so we think the roots are the only ways for them to feed," Vrijenhoek said. Under normal circumstances, when embedded in bone, the roots are invisible.



As yet unnamed--but nicknamed Osedax spiral--this potentially new species of worm lives in mud near bones, rather than directly on bones. When the Monterey Bay team excavated the worms, the researchers found that their long roots penetrated buried bone shards.

"This is particularly exciting to us, because it suggests an answer to the question of why [there are] so many species of bone-feeding worms," Vrijenhoek said. "They appear to be filling different roles in the bone-consumption process. We never expected to find this level of diversity among these animals."