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Scientists Find Elusive Giant Sulfur-eating, Shelled “Worm”

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Scientists Find Elusive Giant Sulfur-eating, Shelled “Worm”

Apr 17, 2017
A three-foot shelled “worm” that looks like a unicorn’s horn? It just goes to show that the great blue planet we live on still holds some surprises. Naturalist Margo Haygood from the College of Pharmacy at the University of Utah tells the tale of how she and her colleagues came upon the odd beast and what it has taught them about the diversity of life on Earth. Learn more here.

Episode Transcript

Interviewer: Scientists have found an animal that's unlike anything you've heard of before, up next on The Scope.

Announcer: Examining the latest research and telling you about the latest breakthroughs. The Science and Research Show is on The Scope.

Interviewer: I'm talking with Dr. Margo Haygood, a research scientist at the University of Utah. Dr. Haygood, describe for our listeners what you and your team have found.

Dr. Haygood: This is a very large animal that looks like an elephant's tusk, probably more than anything, except that it can be either straight or kinked. And inside that white shell is a very long, slippery creature that looks like a giant worm but it's actually a relative of a clam.

Interviewer: And this is big, right? How big are these?

Dr. Haygood: So some of them can get to be taller than me, more than six feet long.

Interviewer: And they're just lying on the sand or where did you find these?

Dr. Haygood: So these animals live in the mud and they're in the mud vertically. And like all clams, they have siphons that carry water across their gills and through their body. And those two siphons stick up out of the sand.

Interviewer: So you just see these little two things sticking out.

Dr. Haygood: Right. And then if you dig it up you have this huge animal.

Interviewer: So why were you looking for this animal in the first place?

Dr. Haygood: Well, these shells had been entering collections in Europe for a couple of hundred years. And it had the fact that they were, these clam-like creatures had been discovered. But no one had ever seen or studied the living animal. And because it's so unusual and so different from its relatives, we wanted to have a look at the living animal and see if we could understand more about how it lives.

Interviewer: How did you get wind of where these shipworms might be in the first place?

Dr. Haygood: Well, that's an interesting story. As I said, one of my colleagues went to a place that had been published by scientists and didn't find them. We knew they had to be there somewhere, and it turned out that one of the younger members of the team was watching television one day and there was a little mini documentary about these strange animals in a fairly remote part of the Philippines. And she reported it to us and we looked at it and we said, "By golly, that's our animal."

And so that allowed us to then make contact with scientists in that region who were very cooperative in helping us to locate the animals and then to actually bring live animals to Manila, to the University of Philippines to our well-equipped laboratory to be able to do the research.

Interviewer: And is that kind of the fun of this for you, kind of the expedition, the search to find something that no one has ever seen before?

Dr. Haygood: Well, for a biologist who's interested in these bivalves, it's like a unicorn. And so, of course, we were looking for it. Of course, we wanted to find it. And we knew before we even began the project in the Philippines that we had hoped to find this animal. And so it was just an incredibly exciting piece of luck when we were able to locate a population.

Interviewer: And what have you learned about it? I mean it has some features that are very unusual. I mean, for example, how on earth does it eat if its mouth is way inside the shell?

Dr. Haygood: Yes. So these animals are members of a group that are commonly called shipworms that live in wood, and they drill and eat the wood. However, these animals are living in sediment and the shell is closed at the end where the mouth is which is the end that's deep in the sediment, so it's very mysterious. How are they making a living? They can't be eating in that situation.

So we looked to see if they might have . . . because there are other large animals that use chemical energy via bacterial symbionts. We looked to see if that might be true in these animals as well. And we found that their digestive tract is very reduced and they have an enormous gill that runs the entire length of the animal. And the gill is where bivalves typically have bacterial symbionts.

And the gill of this animal is full of bacteria that can use the chemical energy that's in the sediment to make food, just the way a plant uses light energy to make food and feed the animal.

Interviewer: So the digestive system of this shipworm is pretty small then, and the bacteria is doing all the eating for it basically.

Dr. Haygood: Right, right. So the digestive system hasn't completely disappeared, but it's very reduced and much simpler than in its wood eating cousins.

Interviewer: And do you think that's helped make this relationship with the bacteria? Do you think that's helped to make this shipworm what it is, given the features that it has enabled it to live where it lives? What is this symbiotic relationship allowed this animal to do, do you think?

Dr. Haygood: Well, the rest of the family use, they eat wood and they use bacteria that can break down wood in order to release the sugar that is the foundation of the cellulose in the wood, so that they can eat that as their food. So a typical shipworm couldn't live in a muddy sediment like this. There would be no food for it.

So what this animal has done is it has switched from these wood eating bacteria to these bacteria that are using chemical energy, which is a very unusual situation, to the type of symbionts completely like that. But it's allowed it to invade a new habitat.

And that's what we see in general in the evolution of symbiosis, that when a host adopts a symbiotic partner, a bacterial symbiotic partner, it allows it to thrive in a new habitat where it couldn't before.

Interviewer: So this was made possible by a collaboration with other investigators and other teams of scientists, right?

Dr. Haygood: So the Philippines is the epicenter of marine biodiversity in the world. And so our project there is to study mollusks in general, snails and clams and other sorts of marine animals. And so this work was a very small part of that and required a big team of Filipino scientists and American scientists working together.

Interviewer: And is that part of the fascination for you to discover something new that's kind of been out there in the world but we just haven't been able to look at it very carefully?

Dr. Haygood: Well, I think that scientists love discovery. There's that moment when whether it's a laboratory result or something in the field, where you're seeing something that no one has ever seen before. And that is just so exciting, it's transient. You get that reward very infrequently. But those moments, they keep you going all your life as a scientist.

Interviewer: So what are discoveries like this show you? I mean I guess things are much more . . . there's a lot more out there than we realize.

Dr. Haygood: Well, to me, one of the exciting things is, we think of this planet as being well explored. But when you're talking about the marine environment, there is so much more to discover. And even pretty conspicuous, large, amazing, peculiar animals like this can still be new to science. And we also see that on land as well, although it's less common. So I think there's plenty more room for exploration and we should not believe that we know all there is to know about the biology of our planet.

Announcer: Interesting, informative, and all in the name of better health. This is The Scope Health Sciences Radio.

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