Scientists Puzzle Over Strange Deep-Sea Worms
Katrina Phillips
In early 2002 researchers at the Monterey Bay Aquarium Research Institute (MBARI) made an exciting discovery – a new species of worm never before seen. The worms were found deep in a canyon of Monterey Bay off the coast of California 2 ,3,5. However it is not the depth at which they were found that make these worms “strange”, it is the bizarre way they live. These worms have no mouth or stomach and only live in colonies on bones of decaying whales. Plus, all the individuals of the colony seem to be female 2,3,5. How can an animal feed with no mouth and reproduce with no males?
This is a compiled image of the whale on which Osedax was discovered in February 2002, taken by the ROV Tiburon at a depth of 2,891m. The dark red colonies of Osedax can be seen on the rib bones.
Image from http://www.mbari.org News 1.
Scientists have found that these whale-bone worms, given the name Osedax, have a similar feeding strategy to hydrothermal vent worms, which also have no mouth or stomach. Both species house bacteria that process nutrients for the worms 2,3,5. The bacteria in the vent worms oxidize sulfur released from the vents and the bacteria in Osedax break down the fats from the whale bones. How do they get to these fats inside the bone? The worms produce root-like extensions that bore into the bone to allow their bacteria direct access to the nutrition within. 2,5
Close-up of a female Osedax taken by Australian marine biologist
Greg Rouse. The green “roots” can be seen at the base of the worn.
So how does Osedax colonize so effectively without males? It turns out that while the males are not readily seen as part of the colony, they are there – inside the females 2,3. Young colonies of females do not show signs of males inside them but after a few months developing on the bones males begin to be observed. The older, larger females contain more males than the younger females – some house over 100 males 4,5! The microscopic males never leave the safety of the females they inhabit which are 2-7 cm in length. It is still unknown, however, exactly how the males fertilize the females, where the males come from in the first place, and how they get inside the females 2,3.
Scientists are eager to study Osedax, but it is difficult to stumble across a whale carcass in the ocean, even when looking for one. The worms have been observed in only a few other places, like off the coast of Sweden, though their distribution could be world-wide. In an effort to learn more about these unique creatures, the MBARI researchers have been dragging beached whale carcasses back out to the bay, attaching tracking devices to them and sinking them so that they can be easily found and studied at a later time. Whale carcasses studied to date have all been colonized by Osedax though larvae have not been found in the water or in the sediment. Researchers have also tested the whale bones themselves, before they are visibly colonized, and have found no trace encysted worms 5.
So it remains a mystery as to where Osedax comes from. How do the worms find whale bones in the middle of the deep-sea? There is still much to be learned from Osedax and hopefully their discovery makes one thing very clear – we have not yet discovered all that the oceans have to offer. Further exploration will no doubt yield more species never seen or described before, not only worms but other invertebrates and possibly vertebrates as well. The first live giant squid caught on tape was only in 2005, and never actually seen in person. Who knows what else could be out there…
References:
1 Fulton-Bennett, Kim. (2002) Whale falls—islands of abundance and diversity in the deep sea.http://www.mbari.org/news/news_releases/2002/dec20_whalefall.html [accessed 9 April 2005]
2 Fulton-Bennett, Kim. (2004) Whale carcass yields bone-devouring worms
http://www.mbari.org/news/news_releases/2004/whalefall.html [accessed 9 April 2005]3 Kane, Daniel. (July 2004) The bizarre case of the bone-eating worms
http://www.msnbc.msn.com/id/5549064 [accessed 9 April 2005]4 Rouse, G. W.; Goffredi, S. K.; Vrijenhoek, R. C. (2004) Osedax: Bone-Eating Marine Worms with Dwarf Males http://www.sciencemag.org/cgi/data/305/5684/668/DC1/1 [accessed 9 April 2005]
5 Jones, Joe. Project Manager/Senior Research Technician Monterey Bay Aquarium Research Institute. 2006 University of South Carolina Marine Science Seminar Series: Tales of the Deep.
