Meet the Scientist Who Studies How Polychaete Worms Wriggle Through the Ocean

The lessons invertebrate zoologist Karen Osborn learns from the tiny worms may have robotic implications

A pink and yellow worm is covered in several tangled strands of string-like gills.
Cirratulidae polychaete worms are covered in tangled strands of external gills. Some researchers refer to them as "hair worms." Karen Osborn

Squirming throughout the ocean are thousands of different polychaetes – short, segmented worms covered in leggy protrusions. With over 10,000 species, they are as diverse as they are bristly. These critters can be found at all ocean depths and temperatures – no matter how extreme – and come in a variety of colors.

One of the largest collections of these wriggly worms in the world is housed at the National Museum of Natural History. The museum even marked July 1st as International Polychaete Day to honor the birthday of longtime Smithsonian polychaete expert Kristian Fauchald.

Fauchald’s successor at the museum today is Karen Osborn. As the curator of polychaetes, her lab serves as the museum’s research hub on these spiny critters.

This World Polychaete Day, Meet a SI-entist who studies the evolution and movement of these delightfully bizarre sea creatures.

As a research zoologist and the museum's curator of annelid worms, Karen Osborn is fascinated by how polychaete worms wriggle through the water column. Karen Osborn

Polychaetes are not critters many people hear about every day. What about them captured your interest as a researcher?

Polychaetes are one of the more visually interesting animals. They come in so many different shapes and sizes and colors and they do so many interesting things. Some of them you can't even tell that they're worms, some look like mice, some look like Vienna sausages, and some look like spaghetti. And many the marine ones come in beautiful colors—some are iridescent, or have these beautiful gold scales on them. They're just immensely fascinating, all the different kinds of them.
Polychaetes, a suite of marine segmented worms, come in a variety of colors and shapes. Some sport fleshy flaps or fan-like feathers while others sprout like Christmas trees. Karen Osborn

They are also so unknown. We probably haven't even described half of the species out there. So, there's a huge diversity of these beautiful, interesting worms that we haven't even got a clue what they're doing, who they are, or how important they are in their habitat. There's a lot to learn out there. And that makes it really exciting because everybody who works on something is contributing to new knowledge.

For instance, one of the worms that we're working on right now has these incredible eyes. There's several undescribed species in this group, and nobody has really ever looked at what their eyes are capable of or how good their vision is. They probably have vision that's as good as a squid—which is about as good as our vision.

What questions about polychaetes guide your research at the museum?

I have a couple of different projects that are focused on polychaetes. One of the projects is looking at how different kinds of polychaetes swim. There are a bunch of polychaetes that live in the open ocean, and they're all pretty different from other polychaetes. I'm interested in how they survive there, and how they've adapted to swimming around their entire life.

We're doing a lot of work with their swimming mechanics, which is fun to try to tease apart. We’re trying to build a model of how they swim so we can play with the shapes, sizes and movement and see how each changes their ability to swim.

One of my other projects is looking at the diversity of midwater polychaetes. Most midwater polychaetes look nothing like other polychaetes, so it's very hard to say which group they are most closely related to. To tell how far they've come and what's changed, it's useful to understand who their common ancestor was.

I'm interested in how animals survive in the midwater and why midwater animals are so dramatically different from all other animals, even from their closest relatives. The only way you can reasonably ask questions like that is if you know their evolutionary history.

We don't usually associate worms with good eyesight. But Alciopid polychaetes sport large, complex eyes that rival those found in octopuses and humans. Their bulging eyes are so large that they can be twice the width of their body. Karen Osborn

What’s interesting and unique about the way polychaetes get around?

We know a little bit about how polychaetes swim from previous studies in the 60s and 70s, and this was before they could do the kind of modeling we can do these days. What they figured out basically suggests that holopelagic polychaetes – or polychaetes that spend their entire lives in the open ocean – should be very poor swimmers. They shouldn't be able to swim very fast and they shouldn't be very maneuverable.

But when we watch them swim with remotely operated vehicles (ROV), we see that they're really fast and really maneuverable. Some can actually outswim our ROVs – one that's just a couple of inches long can outrun our big robot. How are they possibly doing that? Nobody knows how they do it, and so figuring that out has been fun.

What can we potentially learn from researching polychaete movement?

You can apply knowledge of their movement to robotics. There's a lot of interest these days in soft robotics, which is basically robots made out of soft materials. For example, they might want a robot that can swim up an artery and then come back without turning around or damaging the tissue that near.

There are a lot of potential applications for what we’ve learned about the mechanics of how polychaetes move that could be applied to how robots are built to do various things – whether those robots get used on Mars, inside of our bodies, in sewer pipes, underwater exploration, or the various different things that they use robots for these days.

As an inhabitant of the perpetually dark mesopelagic, or twilight zone, region of the deep sea, Tomopterid polychaete eject glowing yellow mucus to deter predators. Karen Osborn

This interview has been edited for length and clarity.

Meet a SI-entist: The Smithsonian is so much more than its world-renowned exhibits and artifacts. It is a hub of scientific exploration for hundreds of researchers from around the world. Once a month, we’ll introduce you to a Smithsonian Institution scientist (or SI-entist) and the fascinating work they do behind the scenes at the National Museum of Natural History.

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