The Small Jelly Creatures That Link Up And Swim In Corkscrews

IRA FLATOW: This is “Science Friday.” I’m Ira Flatow. Later in the hour, Why do some people age more quickly than others? We’ll talk with a scientist who is working to answer that question by developing a molecular index. Plus, the Biden administration is planning to ease restrictions on cannabis. Could that change how scientists study its effects? We’ll meet a team of researchers in Colorado who have found creative ways to work around strict rules on researching cannabis.

But first, I want to spend a little time with some jelly creatures you might not be familiar with called salps. I had never heard of them either. They’re small, transparent, and barrel shaped. They are sometimes confused with jellyfish, but they are so much more complex. They have nervous circulatory and digestive systems, including a brain, heart, and intestines. Wow.

Salps link themselves together in long chains. And each night they journey from the depths of the ocean to the surface to feast on algae. But how exactly do they swim so efficiently? Joining me to talk more about her work studying salps swimming patterns is my guest, Dr. Kelly Sutherland, associate professor of biology at the Oregon Institute of Marine Biology, at the University of Oregon in Eugene. Dr. Sutherland, welcome to “Science Friday.”

KELLY SUTHERLAND: Thanks so much. It’s good to be here.

IRA FLATOW: I never heard of a salp before. Can you fill us in what one is and what makes them so special?

KELLY SUTHERLAND: Yeah, most people have never seen a salp because they live far from shore out in the open ocean. So they’re really adapted to live out in the open ocean. And in order to study them, we have we’ve developed new techniques to be able to meet the animals where they are out in the open ocean. So we’re often going out on boats, and we have custom cameras that we take down to be able to see how these animals swim and move.

Jellies, like salps, are everywhere. And they are often dominant members of open-ocean ecosystems. But we’ve really underestimated how many are out there and what they’re doing.

IRA FLATOW: All right, describe what they look like and how they move about and what they do.

KELLY SUTHERLAND: Yeah. So they look kind of like a pearl necklace. So imagine a long pearl necklace, and imagine that necklace is moving in a spiral or in a corkscrew shape through the ocean. So that’s how some of these animals move.

If it’s a pearl necklace, Each. One of those pearls is an individual organism. So these are colonies of organisms that are interlocked together into these long chains. And they coordinate their behaviors in order to move through the water. So they’re actually swimming using jet propulsion.

So each one of those individuals is about the size of a jelly bean. And the whole chain might be a couple feet long, in the case of the species that we were studying. Each one of those individuals is like a little tube that pulls water in through the front end, and then it squeezes its body and ejects water out the back end. So it’s creating a little jet. And each one of those little individuals along the chain is making its own little jets. And together, collectively, those Jets propel the animal, or the colony, in this case, through the water.

IRA FLATOW: And so they have to coordinate, I imagine, right?

KELLY SUTHERLAND: They do, yes. So one of the things we’ve been interested in is how they’re coordinating those Jets. So we know that individual jellyfish, the jellyfish that you probably think of if imagine a jellyfish, those jellyfish swim by jet propulsion. And it turns out that they are some of the most efficient swimmers on the planet. So it’s a very effective way of moving through the water.

But now imagine that you have a bunch of little jet propellers that are all strung together. And it really opens up all sorts of possibilities in terms of how these animals can now move and maneuver. And it confers additional advantages over the single jetters. Because now you can have more complex maneuvers. And the whole animal can glide really smoothly through the water because at any given moment, one of those jets– or multiple Jets, really, are being activated.

IRA FLATOW: And from the videos I’ve seen, they don’t move in a straight line. They sort of corkscrew through the water, right?

KELLY SUTHERLAND: Yes. So this species of salp is unique in that we found that it was swimming in these corkscrews. We are often scuba diving at nighttime because we want to see these organisms as they come up during their daily vertical migrations. It’s very dark. We use flashlights to be able to visualize the animals.

And we see these long snakelike chains coming up in these big corkscrews, or helices. So they have this really unique way of swimming. The shorter chains, actually, instead of corkscrewing, they spin. So they’re spinning around an axis. And then the longer ones are corkscrewing.

And when we saw this, I mean, besides it just being really stunning and beautiful to see, it’s a really unique way of moving. So helical swimming is something that actually shows up a lot in nature. But all of the previous descriptions have been with microorganisms, so things like bacteria or single-celled algae that swim in a corkscrew. This is a very different case. So instead of a tiny little organism moving in this helical pattern, we have a much larger colony that’s using jet propulsion. So it’s using a very different mechanism to swim in this huge corkscrew.

IRA FLATOW: And you’re saying they journey every night from the depths of the ocean to the surface?

KELLY SUTHERLAND: Yes. So every single night, there’s billions of plankton that swim up to the surface of the ocean. It’s the largest migration on the planet. And we don’t really appreciate it as land dwellers. We don’t think about the fact that the ocean covers 75% of the planet. And a lot of the animals that live in the ocean are undertaking this daily migration, where they swim from deep water up to the surface at night to feed under the cover of darkness.

And then before the sun comes up again in the morning, they swim back down to depth. And it’s really important in terms of energy cycling in the ocean. You have this huge movement coming up and then going back down on a daily basis. And there’s a lot of open questions about how these organisms are able to undertake these long-distance migrations.

It’s kind of the equivalent of you or me running a marathon every single day in terms of their body size. So it turns out that there’s a lot of these animals that migrate that are relying on multiple coordinated units. And we just haven’t really studied very much how this works.

IRA FLATOW: All right, so let me ask you this question, then. If they’re up at the surface, why are you going down so deep in the ocean to find them?

KELLY SUTHERLAND: Yeah, good question. So when we’re out there diving, we are often diving over really deep water. So, for example, we’ve been diving off the Kona Coast of the Big Island of Hawaii, and we go just a little ways off shore. And we’re diving over 8,000 feet of water. So we’re in very deep water, but we’re usually only going about 30 feet deep or so because the organisms are– they might be deep during the day time. They’re ascending towards the surface at night. So we’re meeting them as they journey up to the surface. And so that means that we don’t have to dive deep to be able to observe them and learn about their movements, which is convenient.

IRA FLATOW: Well, you are studying and learning about their acrobatic moves. So why has it taken not just you, but everybody so long to study them?

KELLY SUTHERLAND: Yeah, that’s a great question. So these gelatinous animals like salps are everywhere. And every time I go diving, I’m really struck by– I get down there, and I start to look around. And all around me, I see lots of gelatinous animals. And as a scientific community, we’ve really been underestimating how many of them are there. And that’s because of the techniques that we use. That’s because of the methods we’re using to study them.

So often, as oceanographers, we go out, and we use big nets that we pull through the water. And they just completely destroy something as fragile as a jellyfish. Jellyfish are mostly water. I mean, some of them, some species, you look at them, and they disappear before your eyes. So many of them are very fragile.

And we’ve got to do two things. We have to get to where they are. So in the case of salps that live out in the open ocean, we can’t just dive from shore. We have to get far enough off shore in deep water to be able to observe them. And so that’s been one of the challenges. But the second challenge is we really need to get underwater, either as divers, or we need to use tools that we can take down to visualize them.

IRA FLATOW: Yeah. And you said before that you take a special camera down with you. What is so special about it?

KELLY SUTHERLAND: Yeah. So we’ve actually developed a number of different camera systems. And all of them allow us to see movements and body shapes and colonial architectures in three dimensions. So we have a camera system that’s– we call it a stereo camera system because it has two cameras that act like our eyes.

So our eyes allow us to see things, to perceive things, in three dimensions. Similarly, if you have two cameras, you can get a three-dimensional view of how something is moving through the water. We also have cameras that are a bit like underwater microscopes that allow us to just see really good detail on some of these animals.

And then in some cases, we are very carefully collecting animals. So we collect them by hand in jars. So when we’re diving, we carry around little bags of jars, and we sneak up on the animal and poke it into the jar.

And then back on shore, we do sometimes collect measurements in the lab, but we do so usually within hours of collection. And one of the techniques that we’ve developed is a laser scanning system, where we scan the whole animal, or the whole colony in this case, so that we can see what its three-dimensional shape looks like. So part of understanding this helical swimming pattern required us to really understand the shape of the animals and also, how they interlock together, in order to form that helical shape.

IRA FLATOW: That is cool. Isn’t it always amazing just how much we don’t know about the open ocean?

KELLY SUTHERLAND: It’s true. It is. There’s so much. I’m going to be busy for a long time. There’s so much that we don’t know. And I feel really grateful that I’m able to get underwater with these animals that so few people get to see. They’re really beautiful.

IRA FLATOW: We’re grateful that you have taken time to talk with us today. This was truly fascinating. It was great.

KELLY SUTHERLAND: Yeah, fun for me, too.

IRA FLATOW: Dr. Kelly Sutherland, associate professor of biology at the Oregon Institute of Marine Biology. That’s at the University of Oregon in Eugene. Thank you for being with us today.

KELLY SUTHERLAND: Thank you.

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