South Pole 10. Parasitology and Elephant Seal Lice

In this episode of South Pole, host Clark Marchese interviews Dr. Soledad Leonardi, a parasitologist at the National Research Council in Argentina, about her research on the fascinating interactions between elephant seals and seal lice in Antarctica. They discuss the coevolution of these species, the role of seal lice in disease transmission, and how these parasites have adapted to the extreme conditions of the Southern Ocean. Dr. Leonardi also shares insights into how climate change could impact this delicate relationship and the broader Antarctic ecosystem. Tune in to learn about the unique challenges and discoveries in studying one of the few marine insects in the world.

Episode Guest: Dr. Soledad Leonardi

Browse Dr. Soledad Leonardi’s publications here

Follow Dr. Soledad Leonardi on X 

More information about the National Research Council Argentina here

Episode Transcript  and more information on the Pine Forest Media Website

Follow Pine Forest Media on Instagram @pineforestmedia

Hosted, produced, written, and edited by Clark Marchese 

Cover art and PFM logo by Laurel Wong. 

Theme music by Nela Ruiz

Transcript:

[00:00:09.920] - Clark

Hello, and welcome to another episode of South Pole, the podcast that explores all things Antarctica. I am your host, Clark Marchese, and today we are talking about the fascinating world of parasite host interactions, elephant seals and marine license.

[00:00:40.340] - Clark

We are going to do an episode on elephant seals at some point, but today is not that day. They are only tangential because today we are interested in the lice that lives on and burrows into their thicken fur coats. Our guest for today is Doctor Soledad. Leonardi, a researcher at the National Research Council in Argentina. Doctor Leonardi is a parasitologist who focuses on the interactions between seals and seal lice, and her research explores the coevolution of these two species, disease transmission and how parasites have adapted to the extreme conditions of the antarctic environment and the deep Southern Ocean. Today, we'll focus on how coevolution shapes the interactions between seals and seal lice. In the episode, we'll discuss how coevolution shapes the interaction between seals and seal lice, how the lice have adapted to the process of molting, how they can survive when seals dive 200 meters below the surface of the ocean, and how they have lined up their reproductive schedules with one another. With that, let's go ahead and get started. All right. Well, doctor Leonardi, welcome to the show. The first question I have is if you could just introduce yourself and tell. Us a bit about your research.

[00:02:06.430] - Dr. Soledad Leonardi

Yeah, thanks you, for invite me. I'm Soledad Leonardi. I'm a researcher at the National Research Council in Argentina. I live in Porto Madrid in Patagonia. My research focuses in the co evolution process of lice from seals and sea lions.

[00:02:25.930] - Clark

So today we're talking about parasites and not the Oscar winning film from South Korea. We are talking about seal lice. As a scientist, what sorts of approaches do you take in studying this type of insect?

[00:02:38.680] - Dr. Soledad Leonardi

Yes, well, I'm a parasitologist, so I study the relation between parasites and hosts that are closely related, especially in the case that I'm studying that there are these parasites that were present already when the actual penipeds were terrestrial carnivores, you know, so they go together in the evolution. Colonizing the sea is a process that involves both the lice and the actual pinnipeds. So it's a very interesting question because most of the parasites of these antique animals, extinct when the pinnipeds colonize the sea, will survive.

[00:03:23.180] - Clark

Okay, parasitologists, that's such a cool ology. And another ology word I've seen associated with your work is evolutionary biology, which is a broad based approach that looks at how species originate, change and diversify over time. And I guess you just gave us a great example. As the seals moved into the marine environment, the lice were able to adapt and evolve with the seals, but some other parasites were not.

[00:03:45.940] - Clark

I'm curious if you can tell us why it's important to study biology from this evolutionary point of view.

[00:03:52.380] - Dr. Soledad Leonardi

I think that is because it's a way to understand our world is the basis of any biological study, to understand evolution and the processes, especially, I think, in this context of climate change, that everything is changing so fast. I think that is fundamental to understand the evolutionary processes.

[00:04:14.050] - Clark

So seal lice, that's a very specific niche and very interesting from what I've read so far. What made you interested in studying seal lice in the first place?

[00:04:23.530] - Dr. Soledad Leonardi

Well, in fact, first I was interested in the host, because seals and sea lions are amazing. And then I discovered that they were infested with lice. And I started reading about lice, and it's very curious because there is very little information about sea lice, but they are so amazing too.

[00:04:47.690] - Clark

And so these species are technically an insect, if I'm correct, but they live partially in the marine environment, which we do not see often. Can you tell me a little bit about that?

[00:04:57.610] - Dr. Soledad Leonardi

Yeah, because as everybody knows, insects are the most successful group of animals in earth. Both evolutionarian ecology are the most abundant and the most diverse group of animals. They are present everywhere except in the biggest environment that is the sea. And it's very curious because a group of animals will adapt to so many conditions are absent in the deep of the sea. Most of the species live on the surface of the sea. So the only species that actually live under the sea and are exposure to truly marine conditions are salinity, low concentration of oxygen.

[00:05:36.730] - Clark

Are the lice, do you seal lice exist only in the southern Ocean ecosystem. Or are they throughout the rest of the world?

[00:05:43.890] - Dr. Soledad Leonardi

They're present in every species of seals in the walrus and sea lions are present in other species of penny pups.

[00:05:51.490] - Clark

Okay. And to understand the evolutionary biology of these two species, have they always been able to thrive in the marine environment. Or is that something that came along some point throughout the revolution?

[00:06:01.610] - Dr. Soledad Leonardi

No. Many years ago, they were a kind of a carnivore, similar to another or something like that. And they evolved in these marine forms in a process that took a lot of years to colonize the marine environment. With the particularity that make the difference between other species of marine mammals and dolphins or cetaceans. Pinipers remain with the terrestrial period in their life cycle, you know, they need to go offshore to reproduce, to rest, to mold. This particularity is that made possible, that lies survive, because they need also this time assure this process that is called coevolution.

[00:06:44.980] - Clark

Okay, we have another vocab word. Coevolution is the process by which two or more species reciprocally influence each other's evolution through sustained interaction. Now, this interaction can be mutually beneficial sometimes, or it can be what we call antagonistic interactions, such as predator prey or in this case, parasite host.

[00:07:03.460] - Clark

Maybe we should also define parasite host dynamics. This happens when one organism, the parasite, lives on, or in another, the host.

[00:07:11.070] - Clark

And sustains itself at the host's expense. But then, since we're talking about the.

[00:07:16.440] - Clark

Interaction between species, can you tell us a bit about the interaction between seals and seal lice?

[00:07:22.460] - Dr. Soledad Leonardi

Well, in fact, this is curious because elis use the seedless host, so the seed provides the environment in some way for lice. We are studying if lice, because this particular group of lice are hematophagous insects. That means they eat blood. No, they are blood feeders. It's a characteristic from hematopois insects that they can transmit diseases. So we are studying if impact cell license also act as specters of some diseases to seals.

[00:07:58.920] - Clark

We just did actually have an episode on wildlife diseases with antarctic birds and we've seen, I guess in the worst. Case scenario, some mass mortality events. So can you tell us perhaps just how important seals and pinnipeds are to the antarctic ecosystem?

[00:08:15.100] - Dr. Soledad Leonardi

Yeah, they are considered top predators. They are on the top of food webs together with killer waves. So there also, we call them sentinels of the state of the environment, because if we can detect that something is wrong or is changing with these animals, it's a clue that is changing the entire environment, because in this chain or in this web that is connected since krill to seals, any change in this, well affect the final, that is the top predators.

[00:08:53.560] - Clark

Are we seeing that the seal lice are having a negative impact on the ability of seals to fulfill their ecosystem function?

[00:09:00.600] - Dr. Soledad Leonardi

Well, we don't know. It depends if they actually can transmit some diseases. It's very interesting because last year, for example, there was this epidemic of avian flu that cause a lot of death, especially in Patagonia, silions and elephant seals. And we don't know, for example, if lice are infected with this kind of virus. But in this context of climate change and that the diseases that appear, maybe lice play a particular role, we don't know yet.

[00:09:37.010] - Clark

Okay. And I guess it's only fair since I asked about the seals. So do the seal lice play any important role in the ecosystem?

[00:09:46.020] - Dr. Soledad Leonardi

Yes, I defend the parasites, you know, because the people think that parasites are something that are wrong or that cause the damage or diseases. But in fact, if we think about it, being a parasite is most common than being a free living animal. You know, if we think that every animal on earth are infected, but at least one species of parasites is most common and most abundant, the parasites. So they are a fundamental component in nature. Maybe we can understand because we see the parasites as something that are wrong because they cause diseases on us too, you know, but for nature, there's a mainly component.

[00:10:34.580] - Clark

Okay, interesting. Well, you know, you won't find any.

[00:10:37.340] - Clark

Speciesism on this podcast. There's a couple questions I want to ask you about some articles that you published. One worked on investigating how sea lice are responding to molting. So first, can you maybe tell us what molting is and then also what you discovered about seal lice and what they do during that process?

[00:10:55.960] - Dr. Soledad Leonardi

Now, one of the main features of mammals is that they are covered by hair. Hair is something that they need to change, especially in seals. And there are different kinds of molting. The particular case of elephant seals is that they remove not only the hair, but also the first layers of the skin. So imagine that if the loaves live on the surface, they can disappear with the skin, you know, so the light from elephant seals have the particularity that they borrowed the skin and put under the skin to be protected during this molding.

[00:11:38.380] - Clark

Okay, so that's another example of coevolution. Even if it's a bit creepy, but we will still defend the parasites where we can, I guess. The other article I want to ask. You about discussed the coevolution of seals and seal lice having to do with their reproductive cycles. Can you explain what this article worked on?

[00:11:55.710] - Dr. Soledad Leonardi

Yes, because lice can survive underwater, but there is a main restriction that is related with the fact that eggs don't survive underwater. So for reproduction, lice need to stay enough time ashore to warranty the development of eggs. This time is the same that use the host to reproduce, so there is a coordination between them. When the hosts go ashore to reproduce is the window of time in which lice can do it, too.

[00:12:27.850] - Clark

Okay, that's fascinating, and I guess I'll ask the same question. Is this a recent behavior, or have we seen this happening for a long time?

[00:12:36.210] - Dr. Soledad Leonardi

No, I think that is a consequences. It's a consequence of this coalitionary process is the key that allow the lice can survive. They only survive in species that remain with a terrestrial face in the reproductive cycle, you know, because, for example, baleens or whales and dolphins also have a territory lesion. And maybe the terrestrial forms were infested with lice, but they evolved and completely marine mammals, so they lost the hare. And if they have some lice species, they die unstint, you know, during this process.

[00:13:20.270] - Clark

What other kinds of things do we still need to look into? Are there any other burning research questions when it comes to seal ice?

[00:13:26.910] - Dr. Soledad Leonardi

Well, we are studying now, for example, an elephant seal can reach more than 2000 meters diving. And it's a lot of pressure, you can imagine. And they also depend several months at sea. So lice remain so much for so long without oxygen to breathe. So we are studying how it's possible to see lice to survive under these conditions. And we found, for example, that they can actually obtain some oxygen from the seawater.

[00:14:01.890] - Clark

Wait, like fish do?

[00:14:03.330] - Dr. Soledad Leonardi

Yeah, we don't know the mechanisms they are using to do that, but it's something that we are working now.

[00:14:11.140] - Clark

I'm also curious because climate change is a process that's going to put a lot of species under pressure to adapt quickly. I'm wondering, are there any current or future concerns with how seal lice, or the relationship between the species will evolve as temperatures rise?

[00:14:25.180] - Dr. Soledad Leonardi

Another interesting thing about lice is that because they are insects, there are many changes that we can see now in lice that we use as a proxy of some situations that are living, the marine mammals, the seals, especially in the context of climate change. So maybe we can use some information from lice to understand what is happening with seeds in a process that maybe take a lot of years to see the consequences on seals.

[00:14:58.040] - Clark

Okay, I guess that's just another area we just have to watch this space. Well, as we start to close out the episode, I want to ask if there's anything else you want to add that we didn't mention either about seals, seal ice or research in Antarctica more broadly.

[00:15:11.040] - Dr. Soledad Leonardi

Another thing that is important that I think related to antarctic research, it related with how difficult is to woman to make antarctic science. So when I traveled to Antarctica before my child, it's a lot of work to women that continue working in Antarctica because they feel work take a long time, their month working in a very isolated place in the world. So it's complicated. And here is a little thing that I want to comment that is, well, we are argentinian scientists and we are living a very particular situation now in Argentina because we are with a government that is making cuts in the budget and is against the science. So it has been complicated to make science in Argentina now. Also, the argentinian and antarctic research program is in risk under this government. So I think to remark the importance of the government support to these programs.

[00:16:25.410] - Clark

Well, thank you for sharing that and I guess in that effort, where can people find you and follow your work?

[00:16:31.140] - Dr. Soledad Leonardi

Well, they can follow me on Twitter where I share our last research on news and our work in general.

[00:16:41.980] - Clark

Okay, well, listeners will be able to find that in the episode description. And with that, I want to thank you so much for your time today. Thank you for teaching us about seal lice and also for your very important research.

[00:16:53.100] - Dr. Soledad Leonardi

Thank you for inviting me. It was a pleasure.

[00:17:04.710] - Clark

You've been listening to South Pole. You can find more information about this weeks guest and links to their work in the episode description. Cover art for the show was done by Laurel Wong and the music you're listening to was done by Nela Ruiz. I am your host, Clark Marchese, and this episode was produced and engineered by me. So if you found it interesting, send it to someone you know. South Pole is part of a larger network of sciency podcasts called Pine Forest Media. We've got one on plastic, one on drinking water, and a couple new ones coming out soon. You can find more information about us in the episode description as well or@pineforestpods.com. We are also on Instagram at tikTokineforestmedia. And if you love the show and you want to support science communication like this, a five star rating across platforms and a review on Apple Podcasts is one of the best things you can do to help us reach more people and for the entire network to grow. All right, thank you to all of you who have made it this far and we'll talk soon.