 Aloha and Happy St. Patrick's Day. Welcome back to another episode of A Likeable Science here on Think Tech Hawaii, where each week we examine how our science impacts our own lives, we explore why we all should care about science, and we discover more things to love about science. I'm your host Ethan Allen. As many of you know, I sometimes tell what I call a science campfire stories, tales of unusual animals, plants, or scientists. Sometimes I just spend a few moments talking about these. Today's show is sort of an odd example of how these science campfire stories come to be. My guest today, Rachel Wade, has spent the last several years studying a most unusual animal, an animal that actually captures and uses the energy from sunlight just as plants do. So in honor of St. Patrick's Day, Likeable Science is going green. Welcome to Likeable Science. Rachel, good to have you on the show. Thank you so much for having me. Well, I'm very excited you're here, and let's just start with just a little bit of background. You are a botanist, but you're studying a slug, which as most of us biologists know, is not a plant. Right. So tell us a little bit about how you got involved in this. Sure. So I am a psychologist by trade, so not psychologist, but psychologist, which is someone who studies algae. And since my undergrad, I was always very interested in the interactions between invertebrates and marine animals and the algae they interact with every day. And it was actually the lab manager in my advisor, Dr. Alice in Sherwood's lab, that noticed there was this slug that was very, very common in areas that were mostly dominated by an invasive alga. And we knew that not many things ate this invasive alga. Actually, we didn't know of anything that did. And so we were very curious, what is this slug eating? And what we, when we started to look at the slug, we realized that it was bright green. And looking at a little bit more, we realized that it belongs to this special group of slugs that once they feed on the algae, they sequester and basically enslave the chloroplast from the algae they eat. So just from these humble beginnings of curiosity in the field, my PhD was essentially born to look at the diversity of algae that we can find from those chloroplasts taken in by the slugs. Ah, so you pull the chloroplasts out of the slugs in some way, look at them and can tell what algae they came out of. And so you can tell, is it really eating all the invasive algae or is it selectively picking up other algae that are less common? Exactly. And bottom line is it is eating the invasive algae at least to some extent. Yes, yes. So that's more of a more recent finding. For my masters, I looked at just the diversity and I remember I was very hesitant to get their results back because I thought they're probably eating one thing. They're eating the most abundant thing which may be this invasive or may not be. And they were eating this huge diversity of algae, many of which were new to Hawaii. And so that was really, really exciting. But what we noticed from our preliminary results right away was that they were primarily eating these algae that are very small, so not the ones that are very abundant. These ones that are very difficult to see just even with the trained eye to find in the field. And so we decided to do a little bit of a feeding study and see if there was a preference going on there. Our data suggested there might be. And so we did a nice little feeding study and what we found is that they are preferentially eating these really tiny what we call cryptic, so very difficult to ID with just looking at the algae species. And again, many of which were new to Hawaii or putative new species. So we have a picture here of the slug. Right. So what you'll notice, you see a kind of slit down the back of the slug. And this is due to peripodia that's basically just flaps that these slugs have evolved. And these are very, very important. So it's been shown that these peripodia evolved and have allowed the long term sequestration and retention of these chloroplasts. So for example, there are other species of slugs that do this. We call it kleptoplasty or stealing plastids. But they may only hold on to their chloroplasts for a few days. And they don't have these nice flaps to cover those sequestered chloroplasts. But slugs like Placo brinkus, which is what I study and pictured here, are able to basically fold themselves up like a taco. And by doing that, they're behaviorally shading their chloroplasts, protecting them from too much exposure to the light, which then lengthens the time that they can keep them photosynthetic, which means they'll keep making sugar and food for the slug longer. Okay. So I mean, this is an intriguing phenomenon, right? Because the slug gets these chloroplasts by eating the algae, right? And somehow then in its digestive system, it doesn't degrade it. The chloroplast degrades a bunch of other things, the cells, the algal cells of the chloroplasts that run, but somehow then allows or transports the chloroplasts out to its own skin, right? Right. So specific parts of its skin? Yes, it is very specific parts actually of its digestive system that are stored more superficially on the on the back surface of the slug. So these slugs only feed on what we call syphonous algae. What I mean by that is, even though they can grow to be a meter in length, they are a single cell, which makes it very easy for digestion. So these slugs use a single tooth to pierce the cell wall. And then they have what's called a radula, which is essentially a straw that they used to suck out the cellular contents. And then from there, they have special little extensions of their gut, kind of like our lungs that take up oxygen that engulf the chloroplasts and then filter them into these special extensions of their digestive system. It is very sophisticated because then they must use the rest of the cellular, the cytoplasm all to get the other energy they want. But they're being very efficient about the whole thing. It's very efficient, yes. Very intriguing because particularly in light of the new, the biotech people who are now all working on getting sort of artificial photosynthesis going, right? You know, the slugs figured out how to how to co-opt the plant. Exactly. Very, very neat. So these algae are single celled algae, even though they make the algae, each cell may be actually very, very large. Correct. And but so that the slugs in general are eating very, I mean, small bits of algae because of course, their mouths are actually tiny, right? Exactly. So they can't, they're not going to chew off a big filamentous thing. So are they having impacts, do you think, on the invasive algae? Are they keeping down? Are they hitting the small ones before they can grow big? So that was something when I first began this project and looking at the environment they were in and seeing that they were in habitats that were very much overtaken by this invasive algae, we wondered whether or not they were making an impact. But there was actually a study done not too many years ago in the British Isles, where there's a sister species of slug and an invasive algae. And what they found is that the slug preferentially fed on that invasive algae and was able to control its populations. So if we take a look at that other picture I gave you, we can see our invasive algae in action. And what you can see is that it's doing a really good job of invading. So all of those large mountains, greenish brown mounds are the invasive algae. This is Manalua Bay on the south shore near Hawaii Kai. And yeah, it's it's really, really good at what it does. The slug is the only thing we know that eats it. And so in this environment, the slugs not having a huge impact. However, it may be doing just that in environments that are newly invaded. And that's something I'm hoping to look at a little bit more with the next chapter of my dissertation. Yeah, okay, very intriguing, this unusual interaction. And is much known as sort of a mechanism. I mean, you say it's the chloroplast stay in these branches of the digestive system, but they are just sort of moved along somehow while other material is not. But I don't think that's well understood. There have been some really great physiological studies, but understanding how it's not being digested and it's being maintained. My guess is there's some sophisticated communication going on between the host cells and the algal cells that are not yet identified. Right? Because yes, how is it differentiating between the chloroplast and the nucleus of the chloroplast and the particulum or lysosome or whatever other bit piece organelle of the cell may be. Somehow it's recognizing and selectively treating the chloroplast differently. Exactly. Yeah, yeah. That's that's an amazing accomplishment. Well, that's that's wonderful to learn about. And it seems like it's an animal that tells us some interesting sort of stories, right? Right. Yeah. So that was one thing we did not expect. We did not expect to be able to essentially use this slug as a sampling tool to look at diversity that was otherwise invisible for the most part. It's not these these algae are not easy to go out and find these very small what we usually refer to them as diminutive. We didn't expect to have the opportunity to learn so much more about this invasive alga than we knew before. So it's been really fun to be able to look at an animal and learn about algae. It is not really necessarily what most people would expect. Right, the slug is sort of doing the sampling for you in a way and sampling at a scale that you can't really do very, very easily certain. I guess you could pick up the rocks and take them back to the lab and you can but they're so small. A lot of times they just kind of look like little green fingers coming out of the rock. So very difficult to identify. But the chloroplasts each species of algae are subtly different in some way you can tell. We use molecular techniques. So we are able to extract the DNA from the chloroplasts and use chloroplast specific genetic markers to identify which species they originated from. So this is very very interesting a one off rate because the chloroplasts have their own DNA, correct, but each type of chloroplasts belongs to a specific type of algae that you can associate the one type of DNA with the other. Right. Now very, very, very sophisticated feeding habit as or and of course this is really good to know because we want to know what's happening with these invasive algae. We want to know if the situation getting worse. We sort of think it is right in a crude way. Yeah, so the Department of Aquatic Resources is working very hard to track the spread of this alga and doing continuous surveying and things like that. But my preliminary research and some other research that was done in the early 2000s found that this alga is not always that big, robust, dark green mass that you saw in the picture. Sometimes it can be very small and cryptic just like these other taxa and species of algae I've been talking about. And so what's really helpful again with this slug is because it preferentially feeds on these very small cryptic things, it can be a more selective tool for tracking this alga. The only unfortunate thing is that this doesn't seem to be the first choice for the slug. This may be a last ditch effort of food if there aren't other things available. So that's what you said you did you did a food preference test. Right. So having done some animal training myself and all, tell me a little bit about how do you how do you do it? How do you determine what what food a slug likes? Yeah, so what we did first is we developed a sampling technique to be able to look at the diversity from the field from the slug without killing it. So we basically made it really happy by putting some alcohol into a dish with it, the slug relaxed a little bit as we all do with a little alcohol. And then we just very gently pinched off the very superficial layers of their back, which allowed us to sample some of those chloroplasts. So once we did that, we starved them for 75 days under pretty high light. And what that did was it allowed the slug to clear some of that older chloroplast material out, but also the high light broke down the chloroplast for us a little bit. So once they were no longer green, then we put them in a feeding study. And so what we did for the feeding study is we gave them a lot of those really abundant, large taxa that we had first thought they would like. And then we gave them what we call live rock, which are these small pieces of rock that have a whole community of algae growing on them, and much of which are these little finger like diminutive taxa. And so what we found was that the slugs that had the nice big abundant species didn't feed at all. And the ones that had the live rock were very happy and fed a lot and became green, became photosynthetic, we can measure that we can measure the photosynthetic activity. And we got a molecular or genetic signal from those chloroplasts that we then sampled again. Okay, that's then you could you could tell how many how much of one species versus another. Right. Exactly. Very, very clever. It's it's it is it is fun working with animals. And they're very charismatic. It doesn't help that they're very cute. I see not I suspect not everyone would say that. But yes, I have heard. I have gotten some strange looks. I'm sure when you tell people you work with slugs, people are like, Oh, yeah, they think the brown slimy things in their garden. Absolutely. Not the cute little things with purple horns and blue dots. And about how big are these slugs? They are about two inches long, for the most part. Yes, but they are very sand colored. So it can be difficult to find them in the field. But they're, they're fairly cosmopolitan around Oahu. They're at Waikiki. They're, they're in Manalobe, as I mentioned, they're up in Kaneohebe. So they're quite they're around. Excellent. Excellent. Well, we're going to look into these slugs and algae a little bit more here in the second part of the show. But right now we have to take a break. I'm your host, Ethan Allen here on likable science, Rachel Wade from the UH Department of botany is with me today. And I'm Jay Fidel. And I'm here with Pete McGinnis-Smart to talk about HIGP and research in Manoa. What about that show, Pete? I think it's great, Jay. Research of Manoa really provides faculty members of the University of Hawaii with an easy way of explaining some of the research activities we're conducting on the campus. For example, I do a lot of space research, whether it's the moon and Mars, but many of my other colleagues do other interesting kinds of work, whether it's exploring the ocean floor in submarines, studying earthquakes and tsunamis or other activities. So research at Manoa really provides us with a way of telling the general public some of the activities which we're involved in, as well as communicating to our colleagues and students. This is a fun science. And we really appreciate the activities which research of Manoa enable us to talk about. I love research of Manoa. Come around, join us. It's Monday, one o'clock p.m. Every single Monday. Be there. We'll be square. And you're back here on likable science. I'm your host, Ethan Allen. With me today is Rachel Wade from the UH Department of botany. We are talking about an amazing sea slug whose name I won't even try to pronounce. It's Placo Brancas. Placo Brancas, okay. And what's fascinating, one of the many fascinating things I guess I should say about this slug is that it consumes algae and then co-ops their chloroplasts and uses them and lets them as the picture shows, turns green and captures sunlight and basically uses the sugars I guess that the chloroplasts produce and then those stay in the digestive system and get used for the slug zone growth. And the chloroplast lasts for a while and all. So that's one of the most interesting things about Placo Brancas is that it is the second longest retainer of chloroplasts. So it can keep its chloroplasts happy and photosynthesizing for up to 13 months. So that's a pretty, pretty long time to keep it going. There's one other species, a sister species, Elysia chlorotica that can do it just a little bit longer. But it's pretty amazing, which actually is pretty a hot topic right now as people are interested in, well how does it do this? How is it keeping an organelle that normally relies on a nucleus to tell it what to do? How is the slug doing that? And so there have been quite a few studies looking at what is called horizontal gene transfer. And the idea is if the slug can keep those chloroplasts happy, then maybe they have taken some of the genes from the algal nucleus and co-opted those to continue controlling the chloroplasts. However, no one has found any real conclusive evidence of that yet. So we're still wondering how are they doing this? Right, but obviously the slug is creating an environment at least that is similar enough to the algal environment that the chloroplasts is reasonably happy. Right. And that's, I mean, that's really amazing. That has implication for organ transplants and all. If, you know, we can start putting pig livers into people or whatever you may want to do. I mean, this, that figuring this clever trick on the slug's part out would be a very worthwhile thing to do. Right, and this is something that happens in other organisms, but with whole, whole organisms. So we think about coral, coral something most people in Hawaii know about. So coral have a symbiotic alga, symbiodinium. But the difference is that's an entire alga, whereas this is just a chloroplast. But there has been some really interesting work done showing that the coral has some genes that the symbiodinium needs and vice versa. So they have this very, very close-knit relationship. It must be the same in the slug. We just haven't been able to figure that out yet. But you're right, it has all sorts of implications to understanding symbiotic relationships and enslavement of other organisms. It really speaks to the, as you say, the close-knit relationship. So I mean, can these slugs live without these algae? So that's a good question. So I think they could live without the kleptoplasty. There was some work done a few years ago that showed that Placobrincus in particular is constantly overturning its sequestered chloroplast. So it doesn't eat once and hold onto those chloroplasts. Once it eats again, it will somehow selectively move out those older chloroplasts and replace them with newer ones. So they always have a fresh supply of photosynthesizing chloroplasts. So that to me means that they're not getting a lot of regular nutrition necessarily from the chloroplast. The cytoplasm itself is probably supplying a lot of its necessary nutrition. But why not? Why not have a store on your back at all times for extreme environments? Yeah, exactly. It can't be too biochemically expensive for them to do this, although it seems like a very complicated process to us. But obviously they've figured out some efficient solution, so it pays them off obviously to do it. Right. So if they want, and again this brings up a whole other thing, if they are turning over these chloroplasts, they then have a mechanism to select. They know which chloroplasts are older, presumably because they are maybe being less efficient, putting out less sugars or whatever, but they have a mechanism to process those independently as it were. Right. I mean you see the complexities of this. Exactly. A great example of how life forms interweave and intertwine with one another. Exactly. The classic orchids and the pollinators of specific species of orchids where the birds bills have adapted to exactly the flower shape or vice and or vice versa. Right. So I would say that analogy is definitely applicable to this system. They have developed this sharp tooth and then this straw-like radula to be able to suck out the cytoplasm. I mean this is a very, very good example of co-evolution, just like birds and butterflies and things like that with plants. The other interesting thing about this slug is not only is it enslaving the chloroplasts but it is also using the secondary and defensive chemicals that are produced by the alga to defend itself. So there has been some great chemistry work done to show that placobrancas and other slugs like placobrancas that do kleptoplasty also are stealing those chemicals and making it so they're not tasty anymore. Okay. I mean again some animals are the monarch butterflies with classic example. Right. They eat milk which itself is toxic and they borrow those toxins to make themselves toxic. Yeah. Okay. But no, I hadn't realized these slugs are our plant. So again there's a whole second chemical pathway going on there. Right. And that's got to be processed rather separately presumably because those toxins have to be kept more or less away from the rest of it. Right. Yeah. Wow. Yeah. I'm not as familiar with that work and how what the mechanism of that would be but they're doing it. No, but this is a you know really very pretty picture in a sense of you take research which looks like it should just be it's what some people would say obscure and some people probably would say why are you doing it? It seems worthless and yet here it has all these implications and applications potentially to organ transplant to immunology. Right. To toxicology. Co-evolution, co-speciation. Exactly. Exactly. That's just it's beautiful how sort of everything you're discovering about this is sort of opening up I mean it's a classic you know one good question opens up a dozen more good questions right. Right. Which was unexpected I thought this was going to be a neat little masters and I just had all of these questions and it developed into a whole dissertation. I hear you on that I had when I first went into graduate school I got there at the start of the summer and really didn't have classes or things till the fall so I was just got engaged in a little get-your-hands-what kind of project just to keep me busy that for summer and six years later I had completed a third of that project for my dissertation so I know how layers upon layers upon layers of complexity actually unravel in research. So where do you expect to take this or do you not know? So I have always liked the chemistry component of this so after finishing my dissertation I would love the opportunity to look more at this relationship of co-opting the anti herbivore compounds. I think that's a really fascinating story. The next chapter of my dissertation is looking if we can if we can use this as a gateway to to track averonvillia that very very invasive species. If people are not familiar with it it's commonly known as leather mudweed. Like I said it's really good at being invasive but it's also really good at changing the benthic habitat and that's really a problem here where we have things like corals who live on the hard substrate on the bottom so this alga has a root like system that can hold on to sediment and as a result it can smother corals. So it can have a very dire effect on our coral reefs and the health of our coral reefs. So if we can use this as a gateway to understand that alga more and manage it better that's the direction I would really like to see this go. Can we train the sea turtles to eat the alga? They actually know the sea turtles do a pretty good job with some of our other invasive species just not this one. They don't find it tasty. No, so as I mentioned this slug is the only documented herb before of this plant. It has been seen a fish will take a bite of averonvillia but then they promptly spit it out. It really doesn't taste good. This alga has whole chemicals named after it because they're so nasty. That's the never ending game in evolution is for the plants to try to make themselves as unappealing to their potential consumers and consumers to try to make their digestive systems and mouth parts as robust. So they can deal with all that. Yeah, this alga really has all of the boxes checked for what to do to be really successful especially in a new environment. Yeah, that's what it takes to get by in an ever-changing, repetitive world, right? Right. And speaking of sort of preparing for an ever-changing world so given your experiences and what you've gone through here what would you say to students just sort of considering a career in science? What kind of advice would you give them? That's a really great question so I teach 101 students right now so students who maybe are not interested in science and this is maybe the only science class they take and the big thing I try to emphasize is that anyone can do science. Science comes off as this big scary thing that only really really smart people can do and it's just not true. Anybody can do science, you just have to be interested and want to do it. And I would say right now in our world with climate change and everything that we are facing we need scientists and we need that next generation with new bold ideas to keep pushing. So it may not be the most lucrative career but I would say it's very satisfying. It is. It is endless. The questions are always there, the questions are always new questions are always emerging. Somebody finds something in one field and that suddenly opens up a whole new set of questions in another field and yeah that's truly the intriguing thing about science and what keeps I think scientists coming back from back for more as it works. I think you hit it there and that the need for perseverance is great to get just through the science training certainly. So that's I think one of the issues at graduate school. Yes. Places in front of you is do you really care enough to come into the lab day in and day out? Can you keep pushing for four, five, six years or more? Right now but it's it is as you say it is an intriguing area of study. So well excellent. This has been most fascinating to learn as I do every week on the show. I learn new things and I've learned a ton from you here this week. Great. So I hope at some point I wish of course the best of luck with finishing things up and taking this off into exciting new directions wherever they may lead. Thank you so much for coming on here on St. Patrick's Day and enlightening and in greening I guess our show. Thank you Rachel. Thank you for having me. And I hope viewers will join us again next week for another episode of Likeable Science.