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scene this is the bathroom Disney and Pixar's Elio rated PG the rental guidance suggested only in theaters June 20th you're listening to sleep tight science Did you know that jellyfish don't have a brain, a heart, or even any bones?
What?! They're made of more than 95 % water, which makes them one of the squishiest creatures in the ocean.
Hello friends, and welcome back to Sleep Tight Science, a bedtime show that answers your questions about science.
Have you ever been swimming in the ocean and spotted something floating gently through the water, like a shimmering umbrella with trailing ribbons?
Maybe you've seen one washed up on the beach and wondered, what is that squishy see -through thing?
In this episode, we're diving deep into the mysterious world of jellyfish.
These gelatinous creatures have been drifting through Earth's oceans for over 500 million years long before dinosaurs ever walked the land.
They don't have brains, bones, or hearts, yet they survived through multiple mass extinctions and evolved into thousands of different species.
We'll learn where jellyfish live, how they move, what they look like and how they grow.
From tiny babies smaller than your fingernail to glowing giants with tentacles as long as school bus.
We'll also share some surprising facts about jellyfish and explore other amazing sea life along the way.
So, get cozy and imagine yourself underwater, floating beside one of the that's one of the oldest creatures in the ocean.
Let's learn all about the world of jellyfish, starting right now.
Have you ever seen something floating in the ocean that looked like a shimmering blob of jelly with long, flowing tentacles?
That was probably a jellyfish.
Despite their name, jellyfish aren't actually fish at all.
They don't have bones, hearts, or brains, but they're still very much alive, and they've been swimming through Earth's oceans for over five hundred million years.
Jellyfish belong to a group of sea creatures called Cnidarians.
This group also includes corals, sea anemones, and the Portuguese man of war.
What makes them all special?
Stinging tentacles.
Jellyfish are famous for the tiny stinging cells on their arms called nematocysts.
These cells are like microscopic harpoons.
When something brushes against them, they shoot out and deliver venom to help jellyfish catch their dinner, usually tiny fish or plankton.
Don't worry, though, most jellyfish stings aren't dangerous to people.
Some might feel like a little rash or a mild sting, while others might not hurt at all.
But a few species like the box jellyfish, found in tropical waters, do have very powerful venom and can be dangerous.
So it's always best to admire these creatures from a safe distance.
Even though jellyfish don't have brains, they still sense the world in their own way through a network of nerves that help them respond to touch, light, and chemicals in the water.
Some species can even produce their own light, a process called bioluminescence.
Scientists are very interested in Jellyfish because their unique biology has applications in medicine, like the green fluorescent protein or GFP from crystal jellyfish that helps researchers track cells and compounds in their venom that may lead to new treatments for various diseases.
There are over 2000 types of jellyfish, but scientists group them into several main categories.
The Siphozoa or True jellyfish include familiar ones like Moon jellies and Sea nettles.
The Cubozoa or box jellies have cube -shaped bodies and include some of the most venomous marine creatures.
Other groups include the tiny hydrozoa and the storozoa or stocked jellyfish that attach to surfaces rather than swimming freely.
So, what makes these brainless, boneless creatures so successful?
How do they grow from tiny Let's find out.
Did you know the smallest jellyfish in the world, the Irukandji, is only about the size of a fingernail?
But its sting can be dangerously powerful?!
Jellyfish are some of the most widely spread creatures in the ocean.
They live just about everywhere.
From the warm shallow waters of tropical beaches to the chilly deep seas near the poles, jellyfish have found ways to thrive in remarkably diverse conditions.
In fact, jellyfish are found in every ocean on earth, even in extreme environments that would be inhospitable to most other animals.
Some jellyfish, like the impressive Lion's Mane jellyfish, prefer cold northern waters, and can be found pulsing near the surface in Arctic and sub -Arctic regions.
Others, like the translucent moon jellies, are more commonly seen in warmer coastal waters, sometimes gathering in huge groups called blooms that can stretch for kilometers.
Most jellyfish live near the top layer of the ocean where sunlight shines through and tiny floating plants called plankton live.
The perfect place for a jellyfish buffet.
These upper ocean layers are called the epipelagic zone or more simply the sunlight zone.
That's where jellyfish do a lot of their drifting, hunting, and glowing.
But not all jellyfish stay close to the surface.
Some species can live deep down in the ocean where it's completely dark, the pressure is strong and the water is icy cold.
These deep sea jellyfish are often glowing with bioluminescence, a special kind of light they make inside their bodies which may help them scare predators, attract mates or lure prey.
And while many jellyfish drift freely with ocean currents, some prefer quieter coastal areas or hidden corners near coral reefs, where food is plentiful and the water is a little more protected.
Whether you're swimming in warm ocean water or watching videos of the deep sea, there's probably a jellyfish somewhere nearby, gently pulsing through the water, following the ocean currents that have carried jellyfish for millions of years.
Did you know that jellyfish have been floating through the oceans for over 500 million years?
That means they're older than dinosaurs, trees, and even sharks.
Jellyfish come in all kinds of amazing shapes, sizes, and colors, like floating umbrellas in the sea.
Some are see -through and shimmery like moon jellies, while others glow in the dark using a natural ability called bioluminescence.
Imagine a jelly that lights up like a nightlight underwater.
You might spot jellies in red, orange, yellow, purple, pink, blue, or even glowing green.
Most jellyfish have soft, bell -shaped bodies that look a bit like an umbrella or a clear dome.
That jelly -like bell is what helps them swim.
By squeezing and relaxing, they can gently push themselves through the water.
One group called box jellyfish even has four flat sides to their bell making them shake more like a cube.
Underneath the bell, many jellies have long trailing tentacles and these are more than just decorations.
They're lined with thousands of tiny stinging cells called nematocysts, like microscopic harpoons.
If something brushes up against them, these cells fire off a tiny dart that can sting and paralyze prey, which helps the jellyfish catch dinner.
Most jellyfish stings just cause a little discomfort in humans, but some, like the Australian box jellyfish can be very dangerous.
Jellyfish range from tiny to enormous.
The Irogangi jellyfish, which lives near Australia, is only the size of your fingernail, but its sting packs a big punch. The lion's mane jellyfish, on the other hand, can grow tentacles over 36 .5 meters, or 120 feet long, longer than a blue whale.
Inside their squishy bodies, jellyfish are mostly made of water.
Over 95%. They have no bones, no heart, no brain, and no lungs.
But they do have a simple nerve net that helps them sense the world around them.
Some jellyfish even have basic eyes that can detect light.
Box jellies take it a step further.
They have eyes with lenses and retinas, which can actually form blurry images.
Instead of breathing through lungs, jellyfish absorb oxygen through their skin and they eat and poop out of the same opening.
That's right, their mouth is also their bottom.
Even though they seem simple, jellyfish have survived in the ocean for over 500 million years, much longer than dinosaurs were on Earth.
Their unusual bodies might seem strange to us, but they work perfectly for life, drifting through the sea.
Did you know jellyfish poop out of their mouth?
That's because their mouth is the only opening in their body.
It's a one -way -in, one -way -out kind of system.
You might picture jellyfish just drifting through the ocean like lazy little balloons, but some of them are surprisingly active.
Most true jellyfish float with the ocean currents and gently pulse their bells to move up and down.
But others like box jellyfish are strong swimmers.
They can dart around with quick pulses steering themselves through the water with surprising speed and control.
It's like comparing a floating leaf to a little submarine.
No matter how they move, jellyfish are an important part of the ocean's food web.
Many feed on plankton, tiny drifting creatures like baby shrimp and microscopic algae.
Larger jellyfish are a bit more daring.
They'll eat small fish, crustaceans like crab and shrimp, and even other jellyfish.
They use their stinging tentacles like fishing lines, zapping their prey and pulling it in to eat.
But jellyfish aren't just hunters.
They're also a tasty snack for other sea creatures.
Sea turtles especially love jellyfish and some species, like the leatherback turtle, eat almost nothing else.
Ocean sunfish, a giant flatfish, also munch on jellies.
Even though jellyfish are made mostly of water and don't have much muscle, they are still a key food source for many animals.
Sometimes jellyfish gather in huge groups called blooms. These blooms can include millions of jellyfish floating together like a giant drifting cloud.
Blooms can happen naturally when ocean currents push jellyfish into one area, or when conditions are just right for lots of jellyfish babies to grow up at the same time.
But here's something scientists are keeping an eye on.
Human activities might be changing how often these big jellyfish gatherings happen.
If too many animals that eat jellyfish, like sea turtles, are caught by fishing, or if warming oceans change water temperatures and currents, jellyfish might show up in new places, or in bigger numbers than before.
Some blooms have even blocked fishing nets or the water pipes that cool power plants.
From solitary swimmers to vast shimmering swarms, jellyfish play an important role in ocean life beyond their beautiful appearance.
Did you know jellyfish can clone themselves?
In the polyp stage of life, they can bud off tiny baby jellies that grow into full adults.
Jellyfish may look simple, but their life cycle is one of the most amazing in the ocean.
Most jellyfish only live for a few weeks to a few months, although some can live longer, especially in cooler waters.
But during that time, they go through some incredible changes.
The jellyfish we usually picture, the soft bell shaped body with flowing tentacles, is called a Medusa.
This is the adult form of the jellyfish and it's when jellyfish swim, sting, eat and reproduce.
Like many animals, jellyfish reproduce sexually, which means a male jellyfish releases sperm and a female jellyfish releases eggs into the water.
For most jellyfish, this happens in the open ocean and the sperm and egg meet while floating in the water.
In a few types, the female actually takes in sperm while she's feeding and the eggs get fertilized inside her body.
Once an egg is fertilized, it becomes a planula, a tiny swimming baby jelly.
This little jelly doesn't look anything like an adult.
It floats through the water until it finds a safe spot to stick itself to, a rock or the ocean floor where it turns into a polyp.
Now the jellyfish looks completely different.
The polyp is like a tiny tube stuck to something solid, not swimming around anymore.
But don't let its simple shape fool you, this stage is where the real magic happens.
The polyp reproduces asexually.
That means it makes copies of itself without needing eggs or sperm.
Instead it starts budding or creating tiny copies of itself.
Some polyps create just one jellyfish, like in box jellies.
Others create dozens, or even hundreds, like in true jellyfish.
These tiny new jellyfish eventually break free from the polyp, swim away, and grow into full Medusas.
This back and forth between sexual reproduction in the medusa stage and asexual budding in the polyp stage is called alternation of generations.
It helps jellyfish survive and spread in all kinds of ocean environments.
From drifting babies to stinging adults, the jellyfish's life cycle is full of surprises, just like the jellyfish themselves.
In this episode, we learned all about one of the ocean's most mysterious and mesmerizing creatures, the jellyfish.
We discovered that jellyfish aren't really fish at all, but soft body invertebrates made mostly of water.
We explored where they live – spoiler – almost everywhere in the ocean, what makes their bodies so unique and how they use their tentacles and venom to catch food.
We also learned about their fascinating life cycle – from tiny polyps that clone themselves to bell -shaped medusas that drift and pulse through the sea.
And we also added some surprising jellyfish facts, like glowing bodies, upside down mouths, and tentacles longer than whales.
Jellyfish may look simple but they're full of surprises and they've been floating through earth's oceans for hundreds of millions of years.
Thank you to Beckett from Chapel Hill, North Carolina who introduced our show.
Thank you to Ruby Bobbit age 6 and Josie Bobbit age 4 in New York City, Junie age 8 from St. Charles, IL, Alexandria age 6 from Newcastle, ON, Javica age 8 in Redmond, WA, Silas Shaw age 10 in Bogart, GA, Nordica, age 4 in Oregon, and Remi, age 4 in Squamish, Washington, for asking questions that spark our curiosity and keep us learning.
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Did you know your brain can go on amazing adventures while you sleep?
You might dream about diving deep into the ocean, drifting alongside glowing jellyfish as they pulse through the dark, quiet water.
them again. Maybe you'll shrink down to the size of a sea turtle snack and peek at their wiggly, see -through bodies up close, watching their tentacles dance and their lights flicker like stars under the sea.
Or maybe you'll explore a jellyfish nursery, where tiny baby jellies begin their magical transformation from polyp to medusa.
You could even invent a jelly -powered submarine that floats with the currents, or discover a jellyfish with a new kind of light that twinkles like a firefly.
Whether you're swimming with giants like the lion's main jellyfish or studying the tiniest glowing jellies in the deep, your dreams can take you anywhere.
Who knows? Maybe tonight you'll dream of becoming a marine scientist who helps protect our oceans and the incredible creatures that call them home.
Good night. Sleep tight.
Thank you.
