Magazine article Science News

Gutless Wonder: New Symbiosis Lets Worm Feed on Whale Bones

Magazine article Science News

Gutless Wonder: New Symbiosis Lets Worm Feed on Whale Bones

Article excerpt

Deep-sea researchers have discovered an oddball worm that uses a previously unknown type of symbiosis to feed on whale skeletons--even though the worms have no mouth or gut.

Some other worms from the deep have no digestive systems but depend on live in bacteria for nourishment, explains Robert Vrijenhoek of the Monterey Bay Aquarium Research Institute in Moss Landing, California. The whale bone-raiding worms, in the newly named genus Osedax, likewise rely on symbiotic bacteria. The microbes, from the order Oceanospirillales, reside in green, rootlike growths at a female worm's base. However, the symbionts in female Osedax target an unusual food source--lipids from whale bones that have fallen to the ocean floor--Vrijenhoek and his colleagues report in the July 30 Science.

"We know of no other animal symbiont able to extract lipids," says Vrijenhoek.

The males play out an entirely different nutritional tale. More than 100 tiny males can live inside the sheath that surrounds the female's elongated body. The males don't appear to be parasitic and probably feed off yolk left over from early development. Vrijenhoek rates the males as "little more than larvae."

While females can grow to the size of an index finger, a robust male reaches only 0.3 millimeter in length. "It's the most dramatic sexual dimorphism among worms and may be among the most dramatic in the animal kingdom," says Vrijenhoek.

He and his colleagues discovered Osedax during a 2002 research cruise in Monterey Bay. …

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