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Lightning Strikes Twice
For the Science Curious: Welcome to the Seattle Aquarium’s podcast where we get to spend a little extra time with the experts who appear during our Lightning Talks broadcasts.
Speakers are given a chance to expand beyond the ideas introduced in their 5 minute talks.
Lightning Strikes Twice
Whale barnacles with John Zardus
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Stick with us for a fascinating discussion on whale barnacles! Citadel professor of marine biology John Zardus joins us to talk about some of the best traveled animals in the ocean (despite their lack of legs or fins). John was a speaker at Lightning Talks: Whales (season 6, episode 2). Watch the original talk here.
Find more of John Zardus's work here.
Hello, and welcome to Lightning Strikes Twice, the Seattle Aquarium's podcast where we get to spend a little extra time with the experts who appear during our Lightning Talks broadcasts. My name is Amy Olson. My pronouns are she, her, and I'm a research scientist at the Seattle Aquarium. And I'm joined today with Carrie Garand.
CariHi, everyone. My name is Cari Garand, my pronouns are she, her, and I'm an interpretation supervisor as well as a diver at the Seattle Aquarium. I am excited today to welcome back our guest, Dr. John Zardus. John is the head of the biology department and a professor of marine biology at the Citadel, the Military College of South Carolina. His expertise is in the biology of invertebrate larvae, molecular evolution, deep sea biology, and the biology of symbiosis. In particular, the association of barnacles with both whales and turtles. Welcome, John. So happy to have you with us today.
Dr. John ZardusThank you. Great to be back.
AmyWe last heard from John during Lightning Talks Whales, and you can check that out along with all of our previous Lightning Talks on the Seattle Aquarium YouTube channel. Now, John, I think that you ended your Lightning Talk right before the last of the big red button and where the lightning actually strikes, which is great. That's amazing. Five minutes is not enough time to talk about anything. So now that we do have a little bit of space, is there anything that you had to cut out of your talk and anything you want to share with our listeners now?
Dr. John ZardusWell, I guess one thing I would just have people try to do is think like a barnacle. Now, I don't mean that literally because I I don't think there's a lot of profound thought going on with barnacles.
CariI was real curious as to what that meant. I was like, ooh, think like a barnacle. Okay, so not literally.
Dr. John ZardusNot literally. My idea though is just try to visualize sort of lifestyle they have and what it takes to survive. So think about it, they don't move around, you know, they're just sitting stuck in one place. Their food has to come to them. They can't really go out and get it. So, you know, one of the big important things that a barnacle needs to think about, it's mostly reproduction and feeding. And there's lots of interesting things to talk about in regards to that.
AmyThe cool thing about the barnacles on whales is that they're not, I mean, they're stuck on the whale, but they are traveling far, far distances compared to the barnacles that we see on our local beaches.
Dr. John ZardusYeah, and that's so a general trend that we see with barnacles that are epizoic, that live on other animals, is that they are actually really lazy. The laziest barnacles in the world. And that's because they don't have to do anything to get food. They just stick their fan of cerei out and filter feet in the water as the current rushes past. And in fact, um, I've done some experiments in the lab where I have raised adult barnacles in a chamber with flow. And we were trying to figure out what the maximum flow rate was, the minimum. And it turns out if you have zero flow, they die.
AmyOh no.
Dr. John ZardusThey won't even feed. So they are totally reliant on their hosts for the motion that gives them their food. You know, it hasn't been tested in every species that lives on other animals, but I'll bet you that's a pretty common theme among these ones that are adapted for living on mobile hosts.
CariThat's so interesting. At first, I was like, okay, so what you're telling me is if I was going to be a barnacle, I want to be a barnacle that lives on a whale because I'd have it made. But then if it really that intimate connection between the two, you're so reliant on that kind of host whale to get you everything you need. So choice is really important when you're a barnacle deciding to settle. And in your lightning talk, John, you talked a bit about the process that a barnacle goes through and some of the unknown around how a barnacle is even like that whale, that whale right there. That's the whale that I'm going to settle down on. Can you just talk us through that a little bit more? Or if you have any more tidbits to share around some of the ways that, you know, as a barnacle is going through its planktonic stages and development of life, how do they know it's time? It's time to settle. This is my moment.
Dr. John ZardusYeah, no, great question. And I would love to know some of the answers, but I'll tell you what I know. So barnacles are interesting because they have these multiple larval stages. You know, think of like a caterpillar turning into a butterfly. A barnacle has seven larval stages. So think of like seven caterpillar stages, and then they metamorphose to the adult once they find the appropriate place to attach. So during those seven stages, they are swimming in the plankton, feeding, growing. They cannot attach until they get to that final stage. So they can't bypass any of those earlier stages, or they're not going to make it. It's the final stage only where they're able to attach, and that's called the Cyprid. And the Cyprid has two antenna, antennules they're called, hollow ducts from their head that they secrete glue through. And so what they'll do is they'll come to a surface, and the tips of their antennals have fine little hairs, and they probe the surface, looking, we think, probably looking at chemistry and texture, maybe ionic charge. There's some other properties that of things they may be looking at. And once they've identified an appropriate spot, then they secrete glue through these antennules and are stuck permanently. So if you're a barnacle that lives on a whale, you're only going to release glue once you have encountered the surface of a whale. And it in some cases it has to be the right species of whale. It's not just any.
CariSome are only associated with particular species, right? So they really have a specification of where they're going to glue. And we had a really wonderful question come in from somebody who was watching your lightning talk. I feel like this has got to be another fellow barnacle nerd out there that wants to know is there a scientific term for barnacle glue? Does it have a special name?
Dr. John ZardusMost often it's referred to as barnacle cement. But I have to tell you, the word cement, glue, adhesive is quite fraught. You have the biologists using it, you have the construction engineers, chemists, and not everybody uses the same words in the same way. So glue is perfectly fine, although I think biologists mostly say cement. Oh my gosh.
CariI feel like we've opened up a can of a can of worms around common names. I don't know if that resonates with you, Amy, as a as a research scientist. I feel like I'm always like, Are we talking about the same thing? Yeah, are we talking about the same thing? Or like is the way I'm describing this, is that right? But thank you for clarifying that for us. So we can use barnacle glue, we could use barnacle cement, but depending upon who we're talking to, we might want to be careful and make sure that we're talking about the same thing.
Dr. John ZardusYeah. Just a little technicality. Glues tend to work by drying out.
AmyOh.
Dr. John ZardusAnd cements tend to work, depends on who you talk to, by creating a chemical reaction that causes precipitation and formation of a new compound.
CariInteresting.
Dr. John ZardusSo that does seem to be what barnacles are doing. So they're using a biological cement. They secrete it as a liquid, and it's not drying out because they live in the water, right? But it is cause there is some chemical reaction and it's creating little cross fibers within it that help strengthen it and hold it together.
AmyWow.
CariLittle engineers of the ocean. Okay, this is why barnacles are amazing. I really would love to take like a pre and post survey of this podcast to be like, how many people at the end of this podcast are now barnacle enthusiasts? Barnacles, they are just simply amazing. I just think of them in one way. Barnacles feel like these things that are attached to rocks or whales and they're just kind of there. But I think we're we're talking to the right person here to figure out all the other hidden, the hidden wonders of the barnacles today.
AmyWe did have another really interesting question from a listener. They were wondering how many layers of barnacles are possible on top of each other. And some of the photos you showed, it looked like there were there were multiple layers of barnacles. So how does that work?
Dr. John ZardusYou can get these kind of uh, I don't know, condominium structures of multiple barnacles stacked on each other. That is more common on barnacles that live on the rocky shore, probably, than what you would find, say, on whales. If you think about it, the most of the whale barnacles are living in the skin, and that is the substrate that they are adapted for attaching to. So if they can't get access to the skin, they're not going to be able to attach. So a whale barnacle can't live on top of another whale barnacle. But a rocky shore barnacle could do that, and you can get these little apartment buildings stacked up. How many? I suppose theoretically, it's limitless as long as the ones underneath are able to reach out and feed. If they totally get covered, then they would die. The problem is as you stack up higher and higher, you get more drag and waves and things floating in the water will come and knock them off. So a bigger stack is going to be more susceptible to falling off. So maybe there's some optimum, right? But I'll bet you're probably more than one or two layers thick is more than that is uncommon.
AmyYeah, and thinking about drag, you mentioned during your lightning talk that I think one whale had about a thousand pounds of barnacles. I can't imagine as a whale dragging around that much baggage.
Dr. John ZardusYeah, that's a lot. So that was that was measured from humpback whales, and they in particular seem to be heavily barnacled, more so than other species of whales.
CariI'm so glad you brought up humpback whales because I feel like you're leading us into this other I thought was really interesting question that I never really thought about. And it was particularly, have you ever seen a humpback without barnacles? And I would even extend that to there's quite a few whale species that are known to have associated barnacles with them, but within those species, like a humpback or a gray white whales, you know, do we see them sands barnacles ever? Do they uh are they ever just told naked, smooth-skinned whales? Naked whales!
unknownNo.
Dr. John ZardusNaked whales. Yeah, you know, I trying to think about it. I'm not sure that I have seen one without barnacles. If anything, my guess would be at the fringes of their range. Maybe you would find whales that have fewer barnacles. That would just be a guess. But one thing too is when people look at humpback whales, sometimes they're seeing little bumps in the whale's skin that are called tubercles that sort of look like barnacles, but it's really part of the whale. So it's easy to mistake a barnacle for a tubercle. And yeah, from photos from a distance, you can't always tell for sure. I know other species of whales who sometimes have barnacles and sometimes don't. You often find naked southern right whales and things. Yeah, but the humpbacks, they seem to be the ones that have the most barnacles, and yeah, for the most part, you most of them have them. Yeah.
CariI can't even like I was just trying to think gray whales specifically in my mind. I was like, what would a gray whale even look like without all of that? It just seems like something I've never even seen a photo of. So interesting to to think about that it it is likely kind of always existing. It's like if you have barnacles, you have barnacles, and if you don't, you don't.
Dr. John ZardusWell, and it then there's could be a seasonality to it as well. What we don't really know is when do the whales pick up the barnacles and when do they lose them. We think a lot of the barnacles are only living about a year. So the idea is we think that most of them are picking up the barnacles when they go to their breeding grounds or to their calving grounds in warmer waters in the winter, and that they're picking up small the larvae then are attaching. But then maybe later in the year the barnacles have fallen off. So you might find a naked barnacle late in the year. Sorry, a naked whale late in the year.
AmyYeah, I was wondering when a whale is born in these calving grounds, they they are obviously going to be born without any barnacles. And I wonder if maybe the whales from their mother, the barnacles could reproduce, and that's how they get some larvae. But I also like to think of it in my own mind, which is probably not the case at all. Like they have to be a certain age, like teenagers, and it's kind of like when you start to get acne because your hormones are changing, and so the teenage whales start to get barnacles.
Dr. John ZardusYeah. Yeah, you know, I don't know of any studies that have looked at barnacles on different aged whales. That's an interesting thing.
AmyHere's your next project.
CariI was gonna say next research project already, already set out there. All right. Why don't we take a little bit of a break? We are just gonna pause for a quick moment and we will be right back uh with John for some more audience questions and maybe some of our own as well.
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AmyAnd we're back. So let's take a look at some more of our excellent audience questions. John, we had someone ask, do barnacled whales have a better immune system relative to non-host whales? Which I thought was a really interesting question.
Dr. John ZardusYeah, that is a really great question, actually. And we don't know a lot about that. So I actually had a student who worked on a project with dolphins, where she compared the inflammation levels in dolphins with and without barnacles. And she couldn't see much of a difference. So we have an idea that maybe these barnacles are doing something that evades the host immune system. It's not causing an inflammatory response, which is a typical response. Maybe there's some sophisticated chemical camouflage going on that the whales or the dolphins don't even really know that the barnacle's there. It's a really interesting question because you know, most organisms that these aren't parasites in the typical sense of taking nutrition, but they do penetrate into the host and it's not serious damage, but they're doing something that's a little bit negative. And you would expect the host to respond with some reaction, and we're just not seeing that. And that's a really interesting thing, uh, just in general, and we don't know how the barnacles are accomplishing that. And what's interesting is there aren't too many other things that live on whales and especially on dolphins. So somehow the barnacles have come up with some clever little trick to allow them to live on this substratum. And it and it revolves around the immune system in some way.
AmyDo you think that the whales benefit in uh some other way having these barnacles other than their immune system?
Dr. John ZardusI uh a few ideas have been posed. Uh perhaps it helps in what we call disruptive camouflage. By having barnacles kind of randomly placed, it breaks up the you know, the image of the organism, and so maybe it provides some sort of camouflage. But yeah, I don't know. I mean, they've been evolving together for I don't know, over 30 million years, and so they may have co-evolved in some way that we don't yet recognize that is a benefit to the whales.
AmyYeah, you mentioned in your lightning talk that they might, I don't know if they intentionally use them as kind of like a defense, maybe when they're clashing.
Dr. John ZardusThat's right. So males could uh yeah, a well-armored male might have a better chance against another whale in combat.
AmyBarnacle armor.
Dr. John ZardusYeah.
CariI love how much I learn on these podcasts. I'm just sitting here like, wow, with every new piece of information my love of barnacle grows. As both of you were talking about that. I was thinking about this information that we can also gain from barnacles, essentially, like how that relationship with the whale can help us to also understand what's happening with some of these whale populations and species. And you had talked about measuring isotopes and isotopic signatures in the shell that the barnacle secretes and makes. And that might tell us some information. And so some listeners to the Lightning talk were wondering about do you measure isotopes in the barnacle shells? Kind of like you might measure that in teeth and humans. And you tell us a little bit more about like what is the information we're getting from doing that type of research?
Dr. John ZardusYeah, so it's not something I've personally done, but it has been attempted. So the idea is different water around the globe has different temperatures and different chemical signatures, and as the shell is formed, it incorporates isotopes of the ions around it. And we do know that temperature in particular can affect the isotopic ratio in the shells. And so if an organism is traveling, say a host is traveling from warm water to cold water during the migration season, you can see that change in the isotopic signature in the shell. And so it is one way to see, hey, uh, did this host maybe spend a lot of time or a short amount of time in the war in warm water versus cold water? It's kind of a coarse way to track where they have been all across many months. So it's a good integrative tool, you know, over a long stretch of time. Mostly for migration.
AmyAnd do they commonly measure, is it carbon and nitrogen are the two that I hear about in the Sea Otter world about stable isotope analysis?
Dr. John ZardusYeah, it's mostly carbon, carbon and nitrogen.
CariWell, Amy, do we want to switch gears a little bit? I feel like we have some kind of interesting questions that, well, and some that were general questions that came in from our audience, just wanting to know a little bit more. Which one do you want to ask, Amy?
AmyLet's see. I think we should talk about the media. This one was a really interesting question of how the portrayal of whales in popular media might help or hurt your work.
Dr. John ZardusYeah, interesting. So I think that people probably initially have kind of a negative reaction to barnacles, especially barnacles living on other animals, right? So, oh my goodness, this poor whale is covered in barnacles. It must be suffering. So yes, maybe I have a little bit of an uphill battle sometimes, trying to, you know, fight for the barnacle. Um, I get that. It's totally legitimate. But we do have to remember that these species have been evolving together for a long time. And we don't necessarily know everything about the association. And yeah, the pluses and minuses to having barnacles to not having barnacles. The media perception is probably that barnacles are bad and they need to be gotten rid of. I have talked to aquaria and veterinarians and encouraged them, you know what, if the barnacles aren't causing a problem that you can immediately see, you should probably just leave them be, because they're, you know, part of the natural system. So I would say, yeah, there's probably a little bit of perception that barnacles are bad, but I think I'm able to convince people that no, they're part of the natural system. We need to think about them too.
AmyYeah, in fact, I'm thinking about images of whales that I've seen in, you know, children's books and on the media. And you probably have said this in your head, that whale should have barnacles, but it doesn't, you know.
Dr. John ZardusRight. Oh, yes, for sure. And you know, sometimes I'll see a barnacle drawn, and it won't be quite anatomically correct.
CariBut uh well, I I feel like this is the perfect segue into everybody listening who's like a hundred percent, like I know exactly how you feel. And maybe this is somebody who's really excited about science, research science as a career, about conservation, whether that is for barnacles or whales or whales with barnacles. Any advice for folks that are in that early career phase or maybe exploring a different shift or a pivot in their career? What would you recommend for anybody who's interested in getting into? This kind of work.
Dr. John ZardusYeah, I would say one of the big things is just getting some experience in the field. If you can figure out some way to shadow someone or follow along on some sort of field excursion, we we tend to think we know more than we really do about some of these systems. And it's really easy to be an armchair scientist and to maybe work in the lab. And I'm not denigrating that. That's obviously something we need to do. But I find that a lot of times once you get out on the field, like you know, even me, I've been out there for a while. I'll see things that I have never thought of before. And when you see it in the natural system and how it's really working in the natural world, I think that gives us an opportunity to understand the system better. So if if say conservation is what you're really after, understanding how the animals work and how they live in their environment. We can have all the ideas that we think how they do it, but going out and watching them is really important. And hone your skills of observation to be a keen observer and to be curious and to just ask those wild questions that no one has ever asked before. And yeah, sometimes they're they don't lead to anything, but once in a while we get something new and exciting. So follow your passion and keep your eyes open. I love that.
CariAmy, I just feel like I saw for people who can't see, which is everyone, because this is a podcast. Like, Amy, your smile, like you just like you were like curiosity asking questions. Could see, I can see how much that that connected. Yeah, as another person in the research field. Anything you want to add to that, Amy, I'll ask you that question too.
AmyYeah, I definitely want to second what John said about getting some experience out in the field. In my opinion, the field is always the best place to be. I'd much rather be there than in the lab or on the computer doing analysis and writing. I'd say for young career or students, even, spend some time if you're able to volunteering for organizations or projects. You know, there's often a lot of grad students that need help with their programs. So reach out to folks. And also if you meet someone and you think that is my dream job, I want to study barnacles on whales, but you know, reach out to that person and see if you can get them to chat about their own, their own journey and what experience they have so that it can help guide if you're making a decision about going to grad school or who you're gonna study with or whatnot. You know, ask people about their path there because not everyone has the same path of where they came from and where they got to now. Many of us have very meandering, kind of braided river-like paths to where we are. And so most people are generally welcoming the conversations and and giving some advice.
CariYeah, I think getting people to talk about what they're excited about is not difficult. Exactly.
AmyAnd definitely staying curious, asking questions. There's so much of the world that we don't know and don't understand.
CariI kept thinking, I'm like, we don't know what we don't know sometimes. And the only way to figure that out is to be in it, to make those observations, to start asking questions, to figure out what questions we might need to be asking. Yeah.
Dr. John ZardusWell, speaking of questions, John, is there anything else that we haven't addressed yet that you really wanted to share with our listeners about barnacles and whales? I could talk a little bit about some of the stuff I'm working on right now that is kind of you know at the forefront of the barnacle world. So one thing I'm really interested in are the larval stages of barnacles and how they operate. So the adult barnacle attached to whatever surface we're talking about, we kind of have a feel of what they do. Not a lot, right? They sit there and feed. But how they got there and the forces that are involved in the selection that they made to attach to that particular site, I find really fascinating. So, how do they find their hosts? You know, I'm pretty sure chemistry is a real fundamental part of it. But so I've been looking at the larval stages of the barnacles, and one thing we have recently discovered is that the last larval stage can swim really fast. So Usain Bolt can run as fast as 6.4 body lengths per second. So let's scale this to body length. Okay. So he's the fastest human on the planet. Cheetahs can run 23 body lengths per second. Barnacle Cyprids 35 body lengths per second in the water.
CariWow.
AmyWhat?
Dr. John ZardusYeah. So we're doing some high-speed videography of the swimming. I'm actually working with a colleague at the University of Washington in Seattle on this. And looking at their how they beat their appendages, how fast and what order, and just looking at the whole kinematics of the thing. And then the the question is, why do they need to be so fast? And maybe for something that needs to find a whale. I mean, they can't, you know, they're they're sprinters, they can't do that for a long distance. But when they're close to a host, they might need to move, you know, lightning fast to get in there and attach. So, anyhow, that's kind of a neat finding that we're just we just have recently found. The other thing I'm uh really interested in is using the DNA of barnacles to tell us about patterns in nature. And one question I have is how are the barnacle populations connected genetically? So, you know, we do this with all sorts of species, we do with humans. If you do 23andMe, you can throw your DNA on a map and see how close, you know, who your closest kin, and what part of the world do you have relatives, things like that. Well, we can do that with barnacles. And so I have a funded project right now where we're collecting barnacles from sea turtles from around the globe. So we have 22 locations globally where we're col we're going up to the turtles and collecting barnacles from them and then extracting the DNA from the barnacles and looking at what we call population connectivity. So are the barnacles completely reliant on the sea turtles to carry them about? And are their populations exactly coordinated with the sea turtle populations? We know they have a larval swimming spage, something might be happening there, and they might have a completely different connectivity pattern than the turtles. So this global connection of these barnacles using their DNA is something that really has me interested right now.
AmyThat's fascinating. Job security is all the things that we don't know about whale barnacles. So if you're listening and you want to get into sciences, this is one of those fields that, you know, we could use more folks.
CariStart asking more questions about barnacles. I I kind of want to sneak in one more question. I think we have time because going back to the beginning of our podcast today, you know, I share just how excited I am to be able to talk about barnacles. I've learned so much about barnacles today. I'm wondering, John, what was your moment of like, wow, barnacles? Because it is clear that you are passionate about barnacles, you are still asking all these really interesting things, doing all sorts of amazing research on different aspects of barnacles and their life cycle. Was there a moment in time for you that was like, this is my connection to barnacles? And I just find them to be ceaselessly fascinating. You have to admit, barnacles are kind of like an odd, it's an odd choice compared to, you know, the the the sea otters of the world and the the fuzzy, you know, the charismatic megafaunas, people like to say sometimes. So what what first got you hooked on the barnacle?
Dr. John ZardusYeah, well, okay, so primarily I am a marine invertebrate zoologist. So I love invertebrates to begin with. And it wasn't that barnacles were just the thing that I wanted to do. I loved all invertebrates. And I think it the moment, though, for the barnacle was I took a graduate course in larval ecology where we looked at uh the different invertebrate groups and the larvae they produced, how they swim or don't swim, how they seek out places to attach. And I just started thinking about the barnacles. I'm like, wait a minute, what about those barnacles that live on other animals? That's a very specific place. How do they do that? And it really was just that simple question. How do they do that? And you know, I've been working on it ever since, 25 years.
CariWow, that's amazing. Amazing. You took the words out of my mouth, Amy. I was like, that's amazing. I love it. I just love it. Well, unfortunately, that that is it for this episode of Lightning Strikes Twice. John, thank you so much for being here. We really appreciate being able to spend this time with you learning more, not just about barnacles, but barnacles on whales. This is the whales lightning talks we're talking about in the first place. But if people are still just wanting to know a little bit more, is there anywhere you want to direct them where they can find you or check in on research that you've been doing?
Dr. John ZardusI'm at the Citadel, which is in Charleston, South Carolina, and I'm chair of the biology department. So you can just email me directly if you like. There's no like a barnacle website that I could send you to, unfortunately. But I'm happy to share any information that I have and direct people where, you know, where their interests lead them. And I really appreciate this chance to be on the program and to, you know, give a plug for the lowly barnacle.
AmyCari's right there with you.
CariI really, yeah, I I don't know. I mean, I do know what it is about barnacles, but I won't, I won't continue. Well, I won't go down my rabbit hole of barnacle excitement. But thank you so much, John, for just, you know, being so willing to help answer questions for folks. And thank you all to the listeners for joining us today. Please do keep an eye out for our next regular lightning talks. And remember that you can watch past episodes on the Aquarium's YouTube channel. And I think it is even more important today, it feels to really resonate on this particular episode of the podcast to please stay curious.