Planet Earth - polychaete worms

To understand the sheer variety of life in the seas you have to study all of it from the tiniest bacteria to the largest fish, and then there's the stuff in the middle, such as bristle or polychaete worms. Leticia Gunton studies these polychaete worms at the Natural History Museum's Darwin Centre in London. Now, the worms can reach up to three metres long but as Sue Nelson discovered when Leticia brought out some of her collection there are plenty at the other end of the scale as well.

Leticia Gunton: These worms are from the Whittard Canyon which is an underwater canyon in the North East Atlantic, so it's just South West of Ireland.

Sue Nelson: How big, large is this canyon?

Leticia Gunton: It's pretty big. It starts at a depth of 200 metres and goes down to 4,000 metres. These samples were actually collected from 3,500 metres. The canyon is about two kilometres long.

Sue Nelson: It's funny though that from such a huge structure you should be interested in such tiny worms.

Leticia Gunton: Small worms - well actually in the deep sea most of the organisms are tiny because of the amount of food; there's not much food down there so organisms have adapted to that by becoming very small.

Sue Nelson: So let's have a look at these tiny little polychaete worms under the microscope.

Leticia Gunton: I'm putting under the microscope now, so I will just turn this on; the lights come on and let me get this into focus.

Sue Nelson: They're almost like thin white worms but not so smooth all along in their bodies, slightly disjointed all most, or is that part of the process?

Leticia Gunton: Well, actually, polychaetes are related to earth worms that you find in your gardens. Earth worms have little heads on them for movement as well and so do these polychaete worms and, yes, they are quite small, longish, they're all this colour but they weren't this colour to beginning with they were actually more vibrant colours, it's just the preserving process which makes them all this-

Sue Nelson: It's bleached them out a bit.

Leticia Gunton: Yeah.

Sue Nelson: So why are you interested in these particular worms?

Leticia Gunton: Well polychaetes are actually very abundant in the deep sea. I'm looking at species diversity in the deep sea so I want to understand why there's lot of species in a certain place. I'm working on submarine canyons, underwater canyons and underwater canyons are thought to be hot spots for species diversity and to need to properly understand this I'm looking at the polychaete worms in particular to find if there are lots of polychaete worms found in these underwater canyons. At the moment, yes, I've found there are lots of polychaete worms in underwater canyons.

Sue Nelson: And are there lots of different species of these worms, in particular, and is there much known about them?

Leticia Gunton: I think it's 12,000 species of polychaete worms identified. That's quite a few, identified so far, so the one's I'm looking at and to be honest they're probably all unknown species a lot of them, which makes it quite hard for me when I want to understand species diversity if I'm finding lots of species that are unknown.

Sue Nelson: To my eye they all look very similar under the microscope, particularly when they've lot their colour, how do you tell the different species apart?

Leticia Gunton: With polychaetes they obviously have setae, so the setae are the little hairs going all along down the side of worm, so you can look at the setae and also the prostomium which is the like the head end, so you can see the different shapes of that.

Sue Nelson: Now, one of the ways in which you must compare what you've got here with what you've got already in the Natural History Museum must be with the collections.

Leticia Gunton: Yes, the collections are a really fantastic resource that I have here, I'm very lucky. I think there are 8,000 polychaetes in the collections.

Sue Nelson: Well I think then that we ought to go down to the collection.

Leticia Gunton: Yes, let's go.

Sue Nelson: It feels as if we're going into an air lock.

Leticia Gunton: Yes, it's very high security here.

Sue Nelson: Past two automatic doors.

Leticia Gunton: Yeah two automatic doors and as you noticed in here it's actually a bit cooler.

Sue Nelson: Yes, gosh, quite considerably.

Leticia Gunton:That's to help with the preservation of the specimens down here.

Sue Nelson: Now, it's filled with what look like giant filing cabinets.

Leticia Gunton: Yes, and if I actually open this one here which says polychaeta, polychaete worms that I'm specialising on, and we have all the type specimens and the voucher specimens.

Sue Nelson: Lots of different shaped jars, glass jars here, all sorts of sizes. How many worms are in that because they are so much bigger than the ones that we've looked at which was the size of a hair, whereas these are more maggoty size.

Leticia Gunton: There should just be one in here - they are type specimens. It's actually from a Challenger exhibition-

Sue Nelson: And so you would take this one, say, up to your lab, look under it and compare with what you've actually got.

Leticia Gunton: Yeah, exactly that, to see if it was the same species.

Sue Nelson: And what do you do when you have found a species that you can't find here in the Natural History Museum collection?

Leticia Gunton: Well, so in my deep sea biology ones there are a lot of species that won't be here so what we do is we describe it, like you have to write down all the features, morphological and now actually it moving more towards molecular so you would probably sequence it and then get the sequence information, the DNA from that to come up with a new species.