What is a jellyfish?

0:46 Welcome to Science Is Not Boring by kidopoly.com. I'm Mira. And I'm Finn. Before we dive in, we have some huge shout-outs today. A big hello to Edward, listening all the way in Sydney, Australia. And hi to Shepard, who asked an awesome question. How were dinosaur fossils first discovered? That's a great one, Shepard.

1:10 Back in 1822, a scientist named Mary Ann Mantel was walking in England and spotted some giant fossilised teeth embedded in a rock. They turned out to belong to an iguanodon and it kicked off the whole dinosaur craze. I'd love to just stumble over a dinosaur tooth. Our last shout out goes to Alder, who is six, in Seattle.

1:34 Alder asked, What exactly is inside a jellyfish? That is the perfect question, Alder, because today we are completely focused on your topic. If you haven't already, tap follow wherever you're listening so you never miss an episode. Okay, Mira, I am ready. Hit me with the hook. Imagine an alien-like creature that has been swimming in our oceans for over 500 million years.

2:01 That means they are older than the dinosaurs, older than trees, and even older than sharks. Wait, they survived all the Earth's mass extinctions? They did. And here's the craziest part. They survived for half a billion years, with absolutely no brain, no heart, no blood, and zero bones. No brain? No heart?

2:25 No bones? What even is a jellyfish then? Are they just ghosts of the ocean? They definitely look like ghosts. To answer Alder's question about what's inside them, the answer is mostly water. A jellyfish is 95% water. 95%? If I was 95% water, I'd just be a giant puddle. Exactly. If a jellyfish washes up on the beach in the hot sun, it almost completely evaporates.

2:57 Their bodies are made of just three basic layers. Just three? What are they? The outer layer is the epidermis. The inner layer lines their basic stomach cavity for digesting food. But the middle layer is the cool part. It's a thick, squishy substance called mesoglia. Mesoglia? That sounds like an alien dessert.

3:20 So that's the jelly part? Yep, it's like a structural gel that holds them together. And because they don't have a brain, they use something called a nerve net. It's a web of basic sensory nerves spread all over their bodies. How can they even survive without a brain to tell them what to do? Their nerve net automatically reacts to the world around them.

3:42 It can detect light, changes in water pressure, gravity, and the chemicals of their food. It's like a built-in automatic alarm system. Okay, so where exactly do these brainless water blobs live? Literally everywhere in the ocean. From the freezing Arctic waters to warm tropical coral reefs, and from the sunny surface, all the way down to the crushing depths of the midnight zone.

4:08 So how big can they actually get? Are they just hand-sized squishies? Oh Finn, prepare to have your mind blown. The smallest ones, like the deadly Irakanji jellyfish, are the size of a match head, barely five millimetres across. Okay, that's tiny. I could handle that. But what about the biggest? The biggest is the lion's main jellyfish.

4:31 Its bell, which is the top umbrella part, can be seven feet across, but its tentacles are the real shocker. How long are we talking? Like a school bus? Try three school buses. Their tentacles can reach 120 feet long. That is 36.5 metres. They are actually longer than a blue whale. A jellyfish longer than a blue whale?

4:58 That's terrifying. They have hundreds of these massive hair-like tentacles, and they trail behind them in the ocean current, like a giant floating fishing net. And they sting, right? How exactly does a jellyfish sting work? Their tentacles are covered in thousands of microscopic stinging cells called pneumatocysts.

5:18 Inside each single cell is a tiny coiled-up venomous harpoon. A microscopic harpoon? That sounds like a supervillain weapon. It basically is. When a tiny fish brushes against the tentacle, the cell bursts open. The harpoon fires out in just 700 nanoseconds. Wait, how fast is a nanosecond? A nanosecond is one billionth of a second.

5:44 The jellyfish harpoon accelerates five million times faster than gravity. It is one of the fastest movements in all of nature. Whoa, that happens faster than I can even blink. Much faster. The harpoon punches into the prey and injects venom. But don't worry, most jellyfish venom is designed for tiny plankton, and they don't even notice humans.

6:08 Okay, the lion's mane is giant. But are there any deep-sea weirdos? Things lurking in the dark? Oh, definitely. In 1899, scientists found the giant phantom jelly. It lives 22,000 feet deep in the pitch black ocean. 22,000 feet? That's over four miles straight down. What does a phantom jelly look like?

6:33 It's dark red and black, with a bell shaped like a giant sombrero, and it has four massive ribbon-like arms instead of normal tentacles. They look like 33 foot-long dark velvet curtains floating in the black water. Ooh, creepy. But wait, I heard a rumour once that there's a jellyfish that lives forever.

6:54 Is that true or just a myth? It is 100% true. It's called Teratopsis Dornae, also known as the Immortal Jellyfish. It was discovered in the Mediterranean Sea in 1883. How can anything be immortal? Every animal gets old eventually. Well, when the immortal jellyfish gets sick, stressed, or old, it doesn't die.

7:17 It literally hits the reset button on its own body. Hits reset? Like a video game. Exactly like that. It shrinks in on itself, sinks to the ocean floor, and turns its adult cells back into baby cells. It becomes a polyp again. Wait, that's like an old butterfly turning back into a caterpillar. Can it do that forever?

7:39 As far as scientists know, yes. In a laboratory, one scientist named Shin Kubota watched the exact same jellyfish reset itself ten times in just two years. That is the ultimate superpower. I want to turn back into a baby when I get tired of doing chores. Jellyfish don't just have superpowers for themselves, Finn.

8:01 They actually helped humans win a Nobel Prize. Hold on. A brainless blob of jelly helped humans win the biggest science prize in the world. How? It all started with the crystal jellyfish. They live off the west coast of North America and they glow in the dark. That glowing is called bioluminescence. Glowing jellyfish sound magical.

8:26 What makes them glow? In the 1960s, a scientist named Osamu Shimamura collected 10,000 of these jellyfish to find out. He discovered they have a special chemical called green fluorescent protein, or GFP. So they glow green. Why does that matter for us humans? Because scientists learned how to safely attach this glowing protein to human cells in the lab.

8:52 Now they can literally watch how diseases spread, or how brain cells talk to each other, because the cells light up bright green under a microscope. Whoa! So doctors use glowing jellyfish juice to study human medicine? Yes, and in 2008, three scientists won the Nobel Prize in Chemistry for that exact discovery.

9:15 Jellyfish are literally saving human lives. Okay, I have completely changed my mind about them. They aren't just ocean ghosts, they're glowing immortal medical marvels. And they are also space travellers! In 1991, NASA sent 2,000 jellyfish polyps to space on the space shuttle Columbia. Jellyfish in space?

9:38 Did they wear tiny astronaut helmets? Ha, no, they were in special bags of seawater. Scientists wanted to see how they handled microgravity. Up in space, those 2,000 jellyfish multiplied into 60,000. A space jellyfish invasion! Did they act normal when they came back to Earth? Nope. The ones born in space couldn't figure out gravity when they returned.

10:04 They were completely dizzy and just swam in circles. Alright, Finn, time for the quiz. Are you ready? Born ready. Hit me with those jellyfacts. Okay, first question. How much of a jellyfish's body is made entirely of water? Next one, this is about scale. What is the name of the longest jellyfish, which can grow even longer than a blue whale?

10:36 Question three. Since they don't have a brain, what do we call the special sensory web they use to react to the world? Alright, here's number four. What incredible thing does the immortal jellyfish do when it gets old or sick? Last question. Where did NASA send thousands of jellyfish back in 1991? Great job!

11:10 Let's go through the answers and see how you did. The answer to question one is a jellyfish is 95% water. For question two, the longest jellyfish is the lion's main jellyfish. Number three, the answer is they use a nerve net instead of a brain. Question four, it hits reset and turns back into a baby or a polyp.

11:36 And the final answer is NASA sent them all the way to space. I am still thinking about those dizzy space jellyfish. I guess you really do need gravity to learn how to swim properly. It just shows how incredibly adaptable they are. Surviving on Earth for 500 million years and even taking a trip to orbit.

12:00 If you loved learning about the immortal glowing jellyfish today, please scroll down and leave us a five-star review. It really helps the show. Just scroll down on Apple or Spotify and tap those five stars. And if you haven't already, tap follow wherever you're listening, so you get all our new episodes automatically.

12:20 Oh, and we have sister shows too. History and philosophy is not boring, and maths is not boring. Go give those a listen and a follow as well. And if you want a shout out on the show, or just want to say hi, email us at hello at kidopoly.com. See you next time on Science Is Not Boring. Bye everyone.