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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 teaming with creatures that are stranger, smarter, and more surprising that 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 Hugh. 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. Their beautiful, diverse, interesting, and in his 2022 talk, from TEDxPSU. Zoologist Michael Middlebrooks gives us a deep dive into these fascinating little invertebrates after a short message. And now, our TED Talk of the Day. 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 and 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're 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 have 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 converted 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 zozanthelli. The algae live inside of cells of the coral, captures sunlight and provide the corals with sugar. So effectively, we have photosynthetic animals. This is unusual, but it actually occurs in quite a lot of the corals and many of their relatives. And it 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 and enemies and jellyfish. So this is an upside down jellyfish. This is an organism that just like the corals we were talking about has these zozanthelli inside of them and can photosynthesize. So this animal lives in like 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 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 mullusks. Mullus are probably familiar to some of you because of 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 mullusks are a fantastically diverse group. They are the second most diverse group of animals on the planet after the Arthur ponds which went out because of the insects. But in terms of sheer diversity in body form, the mullus I would argue are in fact the most diverse and range from things smaller than grains of rice to colossal squids that are absolutely enormous. And we have photosynthesis within our mullusks 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 Zosantheli that we saw within the corals. Unfortunately, giant clams are rather difficult to see in the wild. They've been over harvested in many areas because people want their large shells and they're 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 sea shells that you may have collected visiting the beach come from gastropods. So this is a tremendously diverse group of mullus there. The most diverse group of mullus 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 nudie branks. And that name nudie means naked, but brank means gills. So 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, right? So 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, relatives of our corals, like sea anemones. And some of the nudie branks that do that are able to take those zoosantheli 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 sack of gloss and 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 special single little tufts and they just poke one little hole into the algae and 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 into steel, plastic as in chloroplasts. 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 leafs. 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 is lives throughout the Caribbean and the primary one I study, photosynthesize is 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 that 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. It was Michael Middlebrook's 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 Topner, and Tonsika SunglearniVom. Support from Daniella Ballerizo, Christopher Faisi-Bogan, Valentina Bohanini, Ban Ban Chang, Brian Green, and Lainey Lot. Learn more at podcast. TED.com. I am Elise Hugh. I'll be back tomorrow with a fresh idea for your feet. Thanks for listening.