What is an earthworm?

Welcome to Science Is Not Boring by Kidopoly.com. I'm Mira. And I'm Finn. Before we dig into today's topic, we have some huge shout-outs to make. A big hello to seven-year-old Finlay and his sister Sophie, who absolutely love the show and ask for an episode all about worms. This one is just for you two.

And a massive shout-out to four-year-old Hugo and his big brother Luca in Dayton, Ohio, who listen to us together every single day. Hi guys, we are so glad you are here with us.

If you haven't already, tap follow wherever you're listening right now so you never miss a new episode.

Okay, Mira. Finley and Sophie specifically asked for worms. So what is the absolute craziest worm fact you have for us today?

Well, Finn, I want you to close your eyes and imagine a patch of dirt the size of a football field. Just one acre of healthy green farm soil. Did you know that under that grass there can be over one million earthworms wriggling around in the dark right now?

Over one million? Just under one single field? That is so many worms.

It gets even crazier! Every single day, an earthworm eats its entire own body weight in decaying leaves, dirt, and microscopic organisms.

Wait, its entire body weight? If I did that, I'd have to eat like 50 pounds of food every single day. That would be so many hot dogs.

Exactly! They are tiny, unstoppable eating machines. And today, we are going to explore how these little squishy creatures manage to live without any eyes or bones, and how they actually created the rich topsoil that feeds the entire planet.

This is going to be a totally wild ride. Let's get into it. Okay, Mira, so if earthworms don't have any bones at all, how do they even move? I mean, they don't just slide around like jelly on a plate, right?

Nope, they actually have microscopic bristles all over the outside of their bodies, called cetae. They use these tiny, invisible bristles, like anchors, to grab onto the dirt and pull themselves forward through the tight underground tunnels.

Whoa, so they're basically covered in invisible little spikes. That is so cool!

Exactly, and even more amazing, they don't have eyes. Not a single one. But they do have special receptor cells on their front end that can sense light. If they get stuck out in the bright sun for too long, they are in really big trouble.

Why? Because they'll get a bad sunburn without any sunscreen?

Because of how they breathe. Earthworms don't have lungs at all. They breathe oxygen directly through their super thin, moist skin. The moisture traps the oxygen from the air. But if their skin dries out in the hot sun, they literally can't breathe anymore.

Oh no! Is that why you always see them stuck out on the sidewalk after a giant rainstorm?

That's exactly right. When the ground floods with rainwater, they have to quickly come up to the surface so they don't drown in the huge underground puddles. But if they get lost and stuck on dry concrete, it's really dangerous for them.

Wow, being a worm is actually super risky. But wait, if they don't have lungs or bones, do they even have a heart?

Oh Finn, they don't just have one heart.

They have five pairs of tiny hearts. Wait, five pairs? Does that mean they have ten hearts?

Scientists call them aortic archers. They sit right near the front of the worm's body and pump blood all the way through its tiny closed circulatory system. Ten little pumps working together just to keep that worm moving through the dirt.

Hahaha, ten hearts and no bones. That is easily the weirdest animal ever. But why do we care so much about them?

To answer that, we have to talk about one of the most famous scientists in history, Charles Darwin.

Oh, I know him. The guy who studied evolution and went on big ship voyages to look at giant turtles and birds. That's him!

But after he finished travelling the world on a ship called the HMS Beagle, he spent 40 straight years studying something right in his own backyard, at his house in Kent, England.

Wait, he travelled the whole world but then spent 40 years looking at his own backyard? What was he looking at?

Earthworms! Darwin was absolutely obsessed with them. He set up all these wild experiments inside his house, which was called Downhouse, to figure out exactly how smart they were and what their senses were like.

Did he build a tiny worm maze or something like that?

Even weirder! He really wanted to know if earthworms could hear. So he put pots of live earthworms right on a table in his house, and he literally got his son to play the bassoon loudly right next to them.

No way! A famous scientist playing a giant horn to a pot of dirt. What did the worms do?

Nothing at all. They didn't even flinch. He even had his wife Emma play the piano to them. He finally realised that worms can't hear airborne sounds. But when he took the pots and placed them directly onto the piano itself while she played, the worms darted backward into their burrows.

Wait, why would they run away if they can't actually hear the music?

Because they could feel the heavy vibrations of the piano keys shaking the wood. They don't have ears, but they are super sensitive to the ground vibrating. In the wild, that rumbling vibration usually means a hungry mole is digging toward them to eat them.

That is so smart. They use their whole body like one giant ear. But why was Darwin studying them for 40 whole years?

Because he realised they were secretly shaping the entire world right under our feet. Darwin and his kids would go out early every single morning to measure exactly how much dirt the worms were moving in their fields. How do you even measure worm dirt? By looking at worm castings. That's the fancy science word for worm poop.

When worms eat decaying leaves and dirt, they digest it all, grind up tiny rocks in their stomachs, and leave little piles of super rich soil on the surface.

Gross, but also kind of cool. How much of it did they actually make?

Darwin meticulously calculated that in just one single acre of land, earthworms were bringing up about 8 to 18 tonnes of new earth to the surface every single year. That's the weight of three adult elephants, just in worm poop.

Three elephants in just one acre? That means they must be burying everything on the surface.

Exactly! Darwin proved that worms were actually burying ancient Roman ruins and historic monuments. The worms dig underneath, the heavy stones slowly sink into the tunnels, and the worms pile fresh new soil on top. Over hundreds of years, whole giant buildings just vanish underground.

That's like slow-motion magic. Did Darwin write a book about all this worm poop?

He did. In October 1881, right before he died, he published his final scientific book. It was called The Formation of Vegetable Mould Through the Action of Worms.

That is a very long and very serious title. Did anyone actually read it?

Yes, it was a massive bestseller. He proved that without earthworms constantly ploughing the soil, grinding up rocks, and bringing deep nutrients to the top, we wouldn't have the rich topsoil needed to grow plants.

So you're saying that every time I eat an apple or a carrot, I should be thanking a squishy little worm? 100%.

About 95% of all the food produced on Earth relies completely on healthy topsoil. And earthworms are nature's ultimate gardeners, turning dead, rotting leaves into perfect, nutrient-packed plant food.

Okay, I am officially a huge worm fan now. But Mira, are all worms tiny? Like, are there any giant monster worms out there hiding in the dirt?

I am so glad you asked, Finn. Let me introduce you to the giant Gippsland earthworm, which lives in Victoria, Australia.

Wait, how giant is giant? Like as big as a snake?

Oh, bigger. These worms can grow to be about three metres long. That's almost ten feet long.

Ten feet? That's taller than the ceiling in my bedroom. A worm that huge is basically a monster.

Yup, they are as thick as a standard dinner candle, and they live deep underground in dark blue-grey clay soils. And because they are so big, when they expand and contract their long bodies to move through their slimy, wet tunnels, they make a really loud, slurping, gurgling noise.

Imagine walking through a quiet field in Australia and suddenly hearing a giant ten-foot worm slurping around right under your feet. That is completely terrifying. But also awesome.

They are very rare, and actually a protected species down in Australia. They can even live for up to ten years, which is a really, really long time for an invertebrate. Alright, Finn, it's time for the quiz. Let's see if you and our listeners were paying close attention to all these wild worm facts.

Okay, I'm ready. Give me the hardest worm trivia you've got.

First question. How many pairs of tiny hearts, or aortic arches, does an earthworm have pumping inside it? Next one. What are the microscopic bristles called that help a worm anchor itself and move through the dirt? Question 3. What famous scientist spent 40 years studying earthworms in his garden in England?

Here's number four. How do earthworms actually breathe if they don't have lungs? Last question. What is the name of the giant, 10 foot long, slurping earthworm found in Australia? Great job! Let's go through the answers and see how you did. The answer to question one is an earthworm has five pairs of hearts, which means it has ten little pumps.

For question two, those tiny microscopic bristles are called cetae. Number three, the answer is Charles Darwin. He even had his son play the bassoon for them to see if they could hear. Question four. Earthworms breathe oxygen directly through their thin, moist skin. And the final answer is, the giant Gippsland earthworm.

I honestly still can't believe a worm can grow to be 10 feet long and live for a decade. Nature is so surprising.

I just can't believe Charles Darwin spent 40 years staring at worm poop. But I guess it proves that even the absolute smallest, squishiest things can totally change the world.

Exactly. Without them tirelessly working underground, we wouldn't have the rich topsoil we need to grow our forests and our food. If you think worms are wilder than you realised, scroll down right now and leave us a five-star review.

Just tap those five stars, it really helps the show. And make sure to tap follow wherever you're listening so you never miss a new episode dropping. Oh, and we have sister shows too. History and philosophy's 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 and tell us your favorite science fact, email us at hello at kidopoly.com.

Thanks for exploring the crazy underground world with us today, guys. See you next time on Science is Not Boring. Bye.

What is an earthworm?

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