Strange worms discovered
2004-07-30 08:42
Washington - Two strange new species of worms, without eyes or stomachs or even mouths, have been discovered living on the bones of dead whales in California's Monterey Bay.
"Who knows what we can learn here," researcher Robert Vrijenhoek said. "There are many things left to discover in this world. Some we find by accident ... and some we find because we look in places that few people have explored before, as in much of our work in the deep oceans."
In this case, it was a bit of both because the unexpected discovery was made about 2 820 metres below the surface.
Lead researcher Greg Rouse of the South Australian Museum added: "Deep-sea exploration continues to reveal biological novelties" such as this "remarkable" worm.
Vrijenhoek, of the Monterey Bay Aquarium Research Institute in Moss Landing, California, said the worms, ranging from 2.5 to 6.3 centimetres long, have colourful, feathery plumes that serve as gills and green "roots" that work their way into the bones of dead whales. Bacteria living in the worms digest the fats and oils in the whalebone.
Bone eating
The researchers named the worms, a new genus, Osedax, which is Latin for bone eating. Their findings are reported in Friday's issue of the journal Science.
"The worms provide insight into the cycling of carbon that reaches the bottom of the ocean. A dead whale delivers the equivalent of 2000 years of 'marine snow' drifting to the bottom ... where carbon is fixed into organic molecules," Vrijenhoek said. Marine snow is made up of bits of dead fish and other matter than settle to the floor of the sea, feeding many creatures there.
He added that the "worms turn whalebone lipids (fats) into worm eggs and larvae that are carried away from the carcass to produce new worms or to be eaten and dispersed by other animals. This discovery adds to the limited knowledge we have about what happens to organic carbon on the bottom of the ocean".
The worms found eating the whale bones were females.
"Initially we were puzzled why every worm was a female," Vrijenhoek said. He said Rouse took some worms to his laboratory for study and discovered tiny male worms living inside the females.
There were as many as 50 to 100 males within each female, Vrijenhoek said.
The males still contained bits of yolk, as if they had never developed past their larval stage, but they also contained large amounts of sperm.
The female worms, regardless of size, were full of eggs, the researchers noted.
At a loss
"These worms appear to be the ecological equivalent of dandelions - a weedy species that grows rapidly, makes lots of eggs, and disperses far and wide," Vrijenhoek said.
He said a whale carcass may last for decades before it is fully consumed. The carcasses, termed whale fall, tend to be found along migration routes so that eggs dispersed from one whale-eating worm may find another carcass nearby.
At first the researchers - who were actually studying clam ecology - were at a loss to determine what kind of creature they had found.
"They have no mouth, no guts, no obvious segments like all worms are supposed to have," Vrijenhoek said. They looked a lot like little miniature versions" of the strange worms discovered living around hydrothermal vents in the oceans. These vents are cracks in the ocean floor where very hot, mineral-rich water bubbles out from the earth's crust.
So the team extracted DNA from the new worms and discovered they were indeed related to the giant vent worms. The vent worms have colonies of bacteria allowing them to live off sulfides released from the vents, while the new worms have bacteria that digest fats from bones.
The new whalebone worms were divided into two species, and the researchers concluded that the most recent common ancestor lived roughly 42 million years ago, about the same time whales themselves first evolved.
The scientists named the two species of Osedax "rubiplumus" for their red feathery gills and "frankpressi" in honour of Frank Press, a former president of the National Academy of Sciences.
- AP