image: This is a female Osedax, or "boneworm," living on fish bone. view more
Credit: Greg Rouse
A new study led by a scientist at Scripps Institution of Oceanography at UC San Diego is painting a more complete picture of an extraordinary sea worm that makes its living in the depths of the ocean on the bones of dead animals.
Discovered fewer than 10 years ago off Monterey, Calif., but since identified in other oceans, the flower-like marine "boneworms," or Osedax, have been documented mainly living upon whale carcasses that fall to the ocean floor, leading some scientists to argue that Osedax specializes in whale bones. But Scripps Professor Greg Rouse, along with colleagues at Occidental College and Monterey Bay Aquarium Research Institute (MBARI) wondered: Do Osedax boneworms also live on the bones of non-mammals?
To assess the question, the researchers carried out an experiment, which is described in the April 13 online edition of Biology Letters, a Royal Society journal. The team employed MBARI's remotely operated vehicles Ventana and Doc Ricketts to deploy tuna and wahoo bones, as well as shark cartilage inside wire cages at approximately 1,000-meter (3,280-foot) depth off Monterey, Calif. When the researchers retrieved the cages five months later, they found Osedax living on the fish bones, although the shark cartilage had already been eaten by unknown organisms.
"We weren't sure that Osedax boneworms would be able to settle on fish bone and to grow to maturity and breed. When it actually turned out that we could establish all these things it was very satisfying," said Rouse. "That we actually found three different Osedax species living on the fish bones was a further bonus. The finding shows that Osedax boneworms are not whale bone specialists, but are arguably generalists and able to exploit a variety of vertebrate bones."
The finding also lends support to a hypothesis they have previously proposed that Osedax and its bone-eating lifestyle may have evolved millions of years ago during a time known as the Cretaceous period, well before the dawn of marine mammals.
"These bone-eating worms may have expanded their feeding niche several times to exploit the bones of large marine vertebrates as they successively colonized the world's oceans from land," say the authors in the paper.
The scientists say Osedax's ability to exploit non-mammalian bones could be an ancestral trait: "We suggest that whalebones are but one in a long series of food sources that Osedax has exploited and continues to exploit."
"Our experimental studies at MBARI have identified 17 species of Osedax from various depths in Monterey submarine canyon," said MBARI's Bob Vrijenhoek, a paper coauthor. "We now know that the worms are capable of subsisting on a variety of bones from cows, pigs and seals, but this new discovery of Osedax on fish bones forces us to take a fresh look at their nutritional limits and evolution."
The team now plans to further study the possible use of shark remains by Osedax and describe and further understand a host of new species of boneworms they have discovered off Monterey. They also plan to study how the worms actually eat into bone.
In addition to Rouse and Vrijenhoek, coauthors of the study include Shana Goffredi of Occidental College and Shannon Johnson of MBARI.
Funding for the study was provided by the David and Lucile Packard Foundation (through MBARI) and Scripps Institution of Oceanography.
The public can help name a deep-sea worm newly discovered by Scripps scientists, in association with MBARI, as part of Birch Aquarium at Scripps' World Ocean Day celebration. Beginning May 1, the public can submit suggestions for the animal's common and/or Latin name through aquarium.ucsd.edu. The aquarium staff will choose five submissions and ask the public to vote for their favorite. The name will be announced during a special 2 p.m. kelp tank dive show on World Ocean Day, June 8.
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About Scripps Institution of Oceanography
Scripps Institution of Oceanography at University of California, San Diego, is one of the oldest, largest and most important centers for global science research and education in the world. Now in its second century of discovery, the scientific scope of the institution has grown to include biological, physical, chemical, geological, geophysical and atmospheric studies of the earth as a system. Hundreds of research programs covering a wide range of scientific areas are under way today in 65 countries. The institution has a staff of about 1,400, and annual expenditures of approximately $170 million from federal, state and private sources. Scripps operates robotic networks, and one of the largest U.S. academic fleets with four oceanographic research ships and one research platform for worldwide exploration. Learn more at scripps.ucsd.edu.
About UC San Diego
Fifty years ago, the founders of the University of California, San Diego, had one criterion for the campus: It must be distinctive. Since then, UC San Diego has achieved the extraordinary in education, research and innovation. Sixteen Nobel laureates have taught on campus; stellar faculty members have been awarded Fields Medals, Pulitzer Prizes, McArthur Fellowships and many other honors. UC San Diego—recognized as one of the top ten public universities by U.S. News & World Report and named by the Washington Monthly as number one in the nation in rankings measuring "what colleges are doing for the country"—is widely acknowledged for its local impact, national influence and global reach. UC San Diego is celebrating 50 years of visionaries, innovators and overachievers. www.50th.ucsd.edu