Today, we learn 10 Cool Facts about Earthworms. How long are earthworms? Can you eat earthworms? Plus, we learn about the earthworm heart. Listen to my English narration, music, and watch the HD video clips.
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10 COOL FACTS ABOUT EARTHWORMS
10. Partial regeneration
What happens if you cut an earthworm in half? When I was a little kid, I thought you would end up with 2 new worms.
This is 100% not true. All of the earthworm’s vital organs are concentrated on one end, between its head and clitellum. If you cut a worm above the clitellum, both halves will die.
If you cut it below the clitellum, the top half will likely survive and regrow a new tail with an intestinal tract. The earthworm’s nervous system is segmented, which allows regeneration. Also, they have many stem cells, which differentiate into all of the cell types needed to completely regrow their bottom half.
9. Which end is which?
When looking at an earthworm, you might wonder which end is the head. It is actually easy to know. The single band on the worm is called it’s clitellum. This wider, smooth, and less segmented band is always nearer to the head than it is to the butt. Unless you have already cut the worm in half!
The worm’s head doesn’t serve many functions. The mouth is probably the most important feature of a worm’s head. The head contains a tiny brain, about the size of a pinhead, with no teeth, no ears, and no eyes. Earthworms can sense light though, through their skin.
Too much light exposure alone can actually overwhelm an earthworm’s nervous system. Just 1 hour under a bright light can paralyze the worm. Earthworms mostly come out in the dark, and that is why we call them nightcrawlers.
8. Earthworms have 5 hearts
Near the head, earthworms have 5 primitive hearts. They are actually called “aortic arches.” They aren’t valved like human hearts, but they are muscular tubes that pump blood. The earthworm heart is not very similar to human hearts.
They lack a pulmonary system and breathe very differently than us. The pulmonary system circulates blood to the lungs for gas exchange. Worms don’t have a pulmonary system or lungs. Instead, their gas exchange is based on simple diffusion.
Oxygen and carbon dioxide just seep through the skin, into and out of the blood, based on concentration.
Also, all worms are cold-blooded, which means their temperature changes to match the environment they find themselves in.
7. Earthworms like rainy days
Why do earthworms come up when there is heavy rain? A common misconception is that earthworms come up because they are drowning. This is mostly untrue.
They can actually live underwater for over a week! Their breathing by diffusion still functions underwater, but it is dramatically less efficient.
The real reason worms come up is because they need to stay wet, and the rain offers some big advantages. Earthworms wait for heavy rain for opportunities to migrate and mate.
They can move a lot faster on the surface, and this saves them a lot of time looking for mates. Worms don’t need to worry about drying up in a storm.
6. An invasive species after the Ice Age
There are about 4,000 earthworm species on earth. They range from tiny little creatures at 1cm, all the way up to 2 meters in length! But in general, earthworms are very short worms. Some ribbon worms have been measured at 55 meters long!
10,000 years ago, all of the earthworm species in North America were killed off in the Ice Age. After the ice age, the plants in the ecosystem also changed.
Plants like sugar maples and ferns require nutrients from a thick layer of decaying organic matter on forest floors, called “duff.” Earthworms eat the “duff,” and actually harm many modern ecosystems.
Earthworms were reintroduced to America and Canada by ships in colonial times, and 50% of them are considered invasive species today.
5. Hermaphrodites – both mates are mom
How earthworms reproduce is interesting. Each worm has both male and female sex organs. They can’t actually impregnate and clone themselves, though.
They still mate sexually with a new mate, where the major advantage is that both mates can become pregnant to double the offspring produced.
Earthworms have sex on the surface by rubbing their clitellum fluid together. Then, they lay cacoons, which can be produced every couple of days. The egg cacoon gets buried in the ground and hatches after 3 weeks, with up to 7 eggs per cacoon.
Babies take 1 year to grow into adults. Earthworms can live from 2-8 years if they can avoid getting eaten that long.
4. A tasty snack
Many animals call the earthworm food. They are a healthy snack for birds, badgers, and moles. Badgers often eat over 100 earthworms in a single night! Earthworms are 60%- 70% protein.
And that means Earthworms are fantastic because they can turn a pile of dead leaves into a protein and calcium-rich meal! Earthworms don’t have ears, but they can sense the vibrations of predators and try to hide.
Unfortunately, they simply are not fast enough to escape hungry mammals or birds, but they can hide by digging up to 6 feet down.
Even humans like you can eat earthworms. It is a good idea to cook them first to kill any parasites or bacteria.
3. How earthworms move
Earthworms have over 100 segments on their bodies, called “annuli”, and each segment has bristles on it called “setae”. These bristles allow them to move by gripping the soil around them.
Movement is mostly caused by the worm anchoring its rear half, and pushing the front half forward.
Earthworms are constantly contracting and relaxing the muscles of each annuli segment to change length and squirm around.
An earthworm can also dig by eating the dirt in its path and pooping it out to create mucus-coated tunnels.
2. An eating machine
The earthworm digestive system is a relatively simple tube, mouth to anus. Although they do eat dirt to tunnel, they also need to eat organic matter to get calories and nutrients. Earthworms eat about half of their body weight per day.
Their main diet consists of decaying leaves and roots, but they also can eat dead animals. Earthworms can even eat live food like bacteria and microscopic worms such as nematodes.
Earthworms don’t have teeth, but they do have a gizzard to help their digestion. Earthworms store food in something called a “crop,” until it is full. Then, they move the contents into the gizzard.
The gizzard grinds the food up against the dirt and rocks that it has collected. This is how earthworms chew, and the nutrients from the broken-down food are easier to absorb as they pass through the intestines.
1. Natural Recyclers of the Earth
Charles Darwin studied earthworms for 38 years. He was curious about how earthworms help the soil in regard to vegetable production.
Mainly, they improve the soil for farming by digging tunnels. The small tunnels help bring water and air deep into the ground. They also spread around composted nutrients with their excrement.
Earthworm feces are about 10 times more nutrient-dense than the soil around them. Farmers keep worms in gardens on purpose because they can turn food scraps into compost and spread it around.
They are like little automatic soil tillers, and they can do it while plants are already planted.
FINAL THOUGHTS
In conclusion, worms are remarkable creatures that play an essential role in soil health and ecosystem balance. From the common earthworm to the exotic marine varieties, they facilitate nutrient recycling and improve soil structure.
Despite their simple appearance, worms are complex organisms with unique behaviors and characteristics that make them indispensable to life on Earth. Their silent work underground is a testament to the interconnectedness and complexity of our planet’s ecosystems.
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