The Mystery of Sea Creatures (5/5): The fantastically weird world of photosynthetic sea slugs | Michael Middlebrooks

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It is summer where I live and luckily I live near the Pacific Ocean. As the weather continues to heat up, I'm spending more time at the beach. It always makes me wonder what's going on under the water. From the deep sea to the shoreline, the ocean is teeming with creatures that are stranger, smarter and more surprising than most of us could ever dream up. For July's TED Talks Daily playlist, we have gathered five of our favorite talks that dive into the awe inspiring and occasionally mind bending creatures from orcas to kinky fish that live beneath the waves. Happy listening. You're listening to TED Talks Daily where we bring you new ideas to spark your curiosity every day. I'm your host, Elise Hu. Today's talk takes us into the vast depths of the ocean and explores creatures I have to admit I knew very little about, but are totally fascinating. Sea slugs. They're beautiful, diverse, interesting and in his 2022 talk from TEDxPS, zoologist Michael Middlebrooks gives us a deep dive into these fascinating little invertebrates after a short message. This episode is sponsored by Kohler Smart Toilets the objects we interact with most are often the ones we notice least. But what if the most overlooked space in your home could be the most considered? Kohler Smart Toilet challenges that assumption. Their Vail Smart Toilet is a sculptural silhouette that isn't just intentional, it's a philosophy that design changes everything. The kohlervale Smart Toilet is sleek with a rounded shape that's more like architecture than just plumbing, and it goes beyond looks. The touchscreen controls and customizable cleansing features offer a level of comfort and cleanliness that exceeds expectations. It's all about elevating those ordinary daily rituals into something extraordinary through thoughtful design. Kohler has been pushing these boundaries for over 150 years, mastering that balance of stunning form and high performance function that's a long time to get it right and it shows in every detail. Experience the difference of Kohler Smart Toilets. Find out more@kohler.com this episode is brought to you by Dell. Back to school starts now. Get long lasting battery life on the Dell XPS laptop powered by Series 3 Intel Core. So you can work from anywhere now starting at $699 with exclusive student pricing starting at 599. And it's lightweight, portable and packed with enough processing power to make multitasking a breeze. So say goodbye to distractions and hello to more free time because you finished your work faster. Complete your setup with savings on select monitors and more. Must have electronics and accessories limited time deals and free shipping on PCs and more await you at Dell.com deals. That's Dell.com/deals. This message is brought to you by Apple Card. Apple Card puts the power of titanium in the palm of your hand. What does that mean? It means the power to earn unlimited daily cash back on your purchases every day. It means a materially different credit card accepted anywhere in the world. MasterCard is accepted. Ditch the plastic upgrade to titanium, apply in the wallet app on iPhone. Today subject to credit approval, Apple Card is issued by Goldman Sachs Bank USA Salt Lake City Branch terms and more at applecard.com. And now our TED TALK of the day.

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I'm going to talk to you today about sea slugs and solar power, my background and what I do. I'm an invertebrate zoologist. So invertebrate animals are animals that don't have a backbone. So this is actually most of the animals on the planet. It ranges from things like insects to clams to sea sponges to worms and a great other many things that we don't have time to talk about today on our planet. Most of the biological energy that we have available comes ultimately from the sun. The process from this being converted to solar energy to biological energy is photosynthesis. You probably familiar with this as something that plants do. And all of the food that we eat ultimately comes from photosynthesis, either us directly eating plants or eating animals that eat plants. And that's really where all of the energy that all of the animals comes from. However, there are a few animals that have managed to get around that and become photosynthetic themselves and are able to capture the energy from the sun, convert it into biological energy. So just like plants, they take carbon dioxide and sunlight, turn it into sugar and oxygen. The best and most famous example of this are the corals. Corals are able to photosynthesize because of a special partnership, a symbiosis that they have with a single celled algae called zooxanthellae. The algae live inside of cells of the coral, capture the sunlight and provide the corals with sugar. So effectively we have photosynthetic animals. This is unusual, but actually occurs in quite a lot of the corals and many of their relatives and actually happens in a fair number of other animals as well. So we see this in things like some sea sponges, we see this in some flatworms, and we see it in other animals closely related to corals like sea anemones and jellyfish. So this is an upside down jellyfish. This is an Organism that, just like the corals we were talking about, has these zooxanthellae inside of them and can photosynthesize. So this animal lives in shallow mangroves throughout the world and just lays on the bottom capturing sunlight. I keep a few in my laboratory that I use for teaching. And I don't actually have to feed them. I just give them light from one of my aquarium lights. And I've managed to keep some of them there for two years. And I use them in my invertebrate zoology courses. I like the jellyfish, though, even though the coral is perhaps a more famous example. The jellyfish is nice because we can take the tentacle of a jellyfish and look at it under the microscope, and that allows us to see this process. It's quite remarkable that we have animals that are not doing the typical animal thing. The jellyfish can still feed, and in the wild they do. But they can get most of their energy just from the sun. Fantastic. I primarily study a group of organisms called mollusks. Mollusks are probably familiar to some of you, nothing else, because of their shells and in some cases, as food. So these include animals like snails and clams, also things like octopus and squids and some other strange things that we won't have time to go into today. But the mollusks are a fantastically diverse group. They are the second most diverse group of animals on the planet after the arthropods, which went out because of the insects. But in terms of sheer diversity in body form, the mollusks, I would argue, are, in fact the most diverse and range from things smaller than grains to colossal squids that are absolutely enormous. And we have photosynthesis within our mollusks as well. So giant clams, they're fantastically beautiful animals. They live in tropical coral reefs in the Indo Pacific, primarily. And when I say giant, there's a range. Some of the species aren't quite so large, but some of them are absolutely enormous, and they're beautiful. And a lot of the coloration we're seeing in some of these comes from their symbiotic algae. They have the same zooxanthellae that we saw within the corals. Unfortunately, giant clams are rather difficult to see in the wild. They've been overharvested in many areas because people want their large shells, and they are also eaten. That's a very interesting symbiosis, too. But the group that I'm most interested in are called the gastropods. Gastropods are snails and slugs. So your typical garden snail that you may be familiar with. And many of the seashells that you may have collected visiting the beach come from gastropods. So this is a tremendously diverse group of mollusks. They are the most diverse group of mollusks in terms of number of species, quite a large number of them, and they're fantastically interesting. I wish we had time to go into more of them here. The one in the middle is a cone snail, one of the most venomous animals on the planet and also a subject of a great deal of biomedical research studying the potential of its venom. But my real passion is slugs. My favorite thing to do is go scuba diving in a tropical coral reef and look for sea slugs. And a sea slug, ultimately, or any slug, is a snail that, over the course of evolution, has lost its shell. So a slug is just a snail minus the shell. Right. And this has happened multiple times. This was not a single evolutionary event, but one that occurred over and over again. And so we have multiple unrelated groups of snails that have either greatly reduced or lost their shell over the course of evolution. Now, the most common question that I get when I tell people what I do for a living studying slugs is, why would you do that? Why study slugs? You could do anything. They are fantastically weird. They're fantastically beautiful. They do some very strange things. There's a lot of really interesting biology going on with these animals, and there's so much that we don't know. Many slugs, the only scientific paper written on them is a species description, and there's many more out there that haven't even been described. So there's so much for us to learn and so much that we don't know. It's just wide open and so fascinating to me. Now, in the ocean, there are many types of slugs. There's two groups that I'm going to tell you about now. One group is probably the most famous of them and certainly the most diverse in terms of total number of species, are the nudibranchs. And that name, nudie, means naked, but branch, means gills. It's referring to those feathery tufts that we're seeing on these animals. They're beautiful, they're diverse, they're interesting, and they're carnivores. They eat other animals. Mostly they are slugs. They're not chasing things down. They eat other slow things. So sometimes other slugs, they also eat things like sponges and in some cases, or relatives of our corals, like sea anemones. And some of the nudibranchs that do that are able to take those zooxanthellae that we were talking about earlier, put them inside of their own cells, and then they become photosynthetic, so they steal their photosynthesis. They're excellent thieves. Some of them even steal the stinging cells out of jellyfish and anemones and use them for their own defense. Absolutely fantastic. This is my favorite group of slugs, though. These are the sacoglossan sea slugs. They are also thieves. Some of them are green for camouflage, but many of them are green for a very different reason. These slugs are herbivores, and they have a special single little tooth, and they just poke one little hole into the algae, and then they slurp out the contents inside of it, and they take some of those contents and they digest them. But others, the chloroplasts, which are the organelles inside of a plant cell that allows plants to photosynthesize. The slugs take those and stick them inside of their own cells, and then they become photosynthetic. We call this kleptoplasty klepto, as in to steel, plasty, as in chloroplast. So they've stolen chloroplasts. And these slugs, it varies. Some of them can only do this for a couple of days, but some can do this for many months, even complete their entire life cycle. This is wonderful. These animals have stolen photosynthesis. And you can see some of them kind of look like leaves. They're super green. They're fantastically photosynthetic. And how they do this is somewhat of a mystery. Taking a chloroplast and sticking inside of a cell is not enough to become photosynthetic. Chloroplasts need things that the algae provide to them that animals shouldn't be able to do. And we've started to unravel some of this, and this is a slow process and something that we're just really scratching the surface of. But one of the things that we've discovered for the emerald sea slug, which can photosynthesize for its entire adult life cycle, nine months after one meal. And the lettuce sea slug, which lives throughout the Caribbean, and the primary one I study, photosynthesizes three or four months after a meal, Both of these animals are able to make chlorophyll, which is one of the chemicals that is needed for photosynthesis to occur. And animals should not be able to do this, but somehow these slugs have managed to do it. And so this is one of the things that I find really exciting and that we're trying to unravel. But there's so many things that we still don't know about these. So many questions we haven't even thought of yet to ask. What's going on here at the cellular level? What's happening at the molecular level? What's happening at the biochemical level? We're starting to get the answers to these questions, but we really there's so much we don't know yet. Why are some of them blue? I have no idea, but some of our slugs are occasionally this wonderful blue color, something we hope to someday figure out. So I hope you've enjoyed this introduction to sea slugs. I hope this leaves you curious to learn more about slugs and other invertebrates. There's just so much that we don't know and so much out there for us to learn. Thank you very much.

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That was Michael Middlebrooks at TEDx Penn State University in Pennsylvania, US in 2022. This talk was originally published in March 2023. If you're curious about TED's curation, visit ted.com curationguidelines and that's it for today. TED Talks Daily is a podcast from ted. This episode was produced and edited by our team, Martha Estefanos, Oliver Friedman, Lucy Little, Emma Tobner, and Tanzika Sangarnivong. Additional support from Daniela Balarazo, Christopher Fazee, Bogan, Valentina Bohanini, Ban Chang, Brian Greene, and Lainey Lott. Learn more@podcasts.ted.com I am Elise Hu. I'll be back tomorrow with a fresh idea for your feet. Thanks for listening.

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