Science Interviews

Interview

Sun, 27th Mar 2011

Planet Earth Online - Bone Eating Worms

Nick Higgs, University of Leeds

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Diana -   Another source of energy for deep sea species is the bodies of whales and other animals that fall to the sea bed.  Nick Higgs, from the University of Leeds, researches whale fossils, which show tell-tale signs of a much smaller creature that could hold the key to why there’s a gap in the evolutionary record of whales.

" alt="Osedax roseus from whale-1018." />Nick -   They’re called Osedax worms which means “bone devour” in Latin.  They range in size from about the size of your finger to maybe the size of one of your joints.  They look more like little palm trees really.  They have what we call roots that grow into the bone and dissolve it away, and eat the bone, and then they have this long trunk that sticks up out of the bone, and out of that trunk are four palps which are kind of like palm tree branches, but they're bright red to pink and those are the gills of animal.  Those are how it gets oxygen out of the water.

Sue -   They sound quite beautiful actually, but the way you describe them, they sound extremely destructive.  Have you found evidence of these worms in whale fossils?

Nick -   Some scientists have, yes, from fossils in Washington state in the USA and we’re currently investigating some other fossils from Italy.  There are some exciting signs, but it requires a bit more work.

Sue -   When you went down to Kent, you got the call, you went to see the stranded sperm whale, what did you get out of it?  What did you want from it?

Nick -   Well we were going down to get some bones that we could put on the seabed to try and find some of these Osedax worms, and we came back successfully with a whole flipper which has got several nice bones in it that the worms like.

Sue -   The flipper is currently at the Natural History Museum before being deployed, but inside Leeds University’s Palaeontology Lab clean room, Nick can study other animal bone samples where Osedax worms were also found...

...Several jars here.  The sort that you would expect to see a lot of chutney in, “sponge-like” in appearance...

Osedax frankpressi from whale-2893.Nick -   This was from an elephant seal carcass that was put down in the same area that they had previously sank the whale carcasses, to see if these worms would also like the bones of other animals as well.  We’re starting to think that they might have a much bigger impact on the fossil record of not just whales, but any marine vertebrate.

Sue -   Well let’s take a couple of these jars back in, out of the clean room, away from the noise of the fume cupboard, and into the lab.  What am I looking for?  I'm not going to see any worms in this am I?

Nick -   No.  You may just see some of their tubes hanging out of the bone because they tend to dry up in the alcohol.  They don't quite look as magnificent as they do in real life, but can you see here this kind of parchment-like bits sticking out of the bone?  Those are the tubes.

Sue -   This tiny little tube.  Almost look like sort of rolled up spider’s webs.

Nick -   Yeah.  They've decomposed because they've been in the jar for so long.  You can see there are several small holes on the bone and I don't know if you can just tell if I change the light slightly.  There's a kind of mottled colour to the bone surface.

Sue -   I can see that, yes.

Osedax rubiplumus from whale-2893.Nick -   That's the extent of where they bored away the bone underneath the surface.  So all that black area is where the bone has been eaten away.

Sue -   Why is it so important to know the effect that your bone-eating worms have on a whale?  Is it purely so that you know that you've got the correct age of a whale fossil or is it more basic than that?  Do they have such an effect on it that you can't necessarily tell what the creature is or when it was from?

Nick -   Exactly.  Within 10 years, they may be able to eat away whole bones.  So in which case, we’d have no record of that whale ever existing whereas in some whales, like the one I'm investigating in Italy, a lot of the bones were found and couldn’t really be properly described because they were so mangled and partially destroyed by these worms.  What I'm really interested in is figuring out whether the gaps in the fossil record of whales may be caused by these worms.  There's a significant period in the evolution of whales when they become ocean going, when they move away from shallow habitats, and we get this gap in the record which is incredibly tantalising because at the next stage after this gap, you start to see what we know as the ancestors of modern whales, the toothed whales and the baleen whales.  But there's this tantalising gap when they started moving out into open water which is exactly when the carcass would’ve started arriving in the Deep Sea.

Diana -   Nick Higgs from the University of Leeds, who’s hoping to discover whether Osedax worms are responsible for the gap in the fossil records of whales.

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