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Noted by Kevin Stewart:
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'Zombie worms' found off Sweden

18 October 2005

A new species of marine worm that lives off whale bones on the sea floor has
been described by scientists.
The creature was found on a minke carcass in relatively shallow water close to
Tjarno Marine Laboratory on the Swedish coast.

Such "zombie worms", as they are often called, are known from the deep waters of
the Pacific but their presence in the North Sea is a major surprise.

A UK-Swedish team reports the find in Proceedings of the Royal Society B.

Adrian Glover and Thomas Dahlgren tell the journal the new species has been
named Osedax mucofloris, which literally means "bone-eating snot-flower".

"They look like flowers poking out of the whale bone. The analogy goes a bit
further because they have a root system that goes into the bone," Dr Glover, a
researcher at London's Natural History Museum, told the BBC News website.

"The part of the animal that is exposed to the seawater is covered in a ball of
mucus, so they are quite snotty. That is probably a defence mechanism."

Global distribution

Scientists have recently begun to recognise the importance of "whale fall" to
ocean-floor ecosystems.

When the great marine mammals die and drift down to the sea bed to decay and
disintegrate, they provide a food resource for a host of different organisms.
Finding these locations to study is not easy, though.

In October 2003, Glover and Dahlgren sank the remains of a dead, stranded minke
whale in 120m of water and monitored what happened to the carcass over a period
of months using remotely operated vehicles.

In August 2004, the team was able to recover a bone from the skeleton.

To their astonishment, it hosted a type of marine worm previously only thought
to exist at great ocean depths - down to almost 3km in the Pacific on the bones
of gray whales.

Glover and Dahlgren say there are remarkable similarities between the worm
species, despite being separated by two ocean basins and more than 2,500m in the
water column.

Hunting impact

Osedax worms are about 1-2cm in length.

They root themselves to the whale bones which they then plunder for oils with
the help of symbiotic bacteria. The worms' flower-like plumes pull oxygen from
the water.

Their reproductive system is extraordinary - certainly in the case of the
Pacific Osedax.

"The female Pacific worms keep males inside their tube as a sort of little harem
that fertilises eggs as they are released into the water column," explained Dr
Glover.

"We're not sure what's happening with the reproductive biology of the Swedish
worms yet. We've only got females; we haven't found any males. It's a bit
weird."

Scientists have established that all of the Osedax species so far identified
appear to be closely related to vestimentiferan tubeworms, which are found only
at the volcanic cracks in the ocean floor called hydrothermal vents.

This has given rise to the theory that whale falls may act as "service stops",
or hopping points, that allow some lifeforms to move around the ocean floor.

What concerns researchers is that the commercial hunting which so devastated
whaling populations would also have severely curtailed this activity by reducing
the incidence of whale fall.

It may even have led to the extinction of some bottom-dwelling organisms that
depended on this rare but concentrated nutrient supply.

Glover and Dahlgren, who is affiliated to Goteborg University, intend to study
their North Sea worms further in the laboratory.

http://news.bbc.co.uk/2/hi/science/nature/4354286.stm