10 Incredible Earthworm Facts

Written by Jeremiah Wright
Published: June 22, 2022
Image Credit iStock.com/K-Kucharska_D-Kucharski
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An earthworm is a terrestrial annelid invertebrate that belongs to the Lumbricidae family. Earthworm derives its name from where it lives (earth). They are adaptable to any biome with moist soil or dead plant material. They are most abundant in rainforest areas and freshwater.

Earthworms are smooth-skinned worms with a tube-within-a-tube segmented body plan. Each segment is covered with a row of bristles called setae. These bristles anchor them on the ground and are the inspiration behind the scientific name “Oligochaeta.” Oligochaete translates to “few bristles.”

It turns out that these worms are incredible and play significant roles in the ecosystem. Earthworms are very important for improving the quality of the soil, such as its moisture, ability to hold water, and nutrient content.

Here are ten incredible facts about earthworms.

1. Earthworms are hermaphrodites

close up of an earthworm
Earthworms possess both male and female body organs, making them simultaneous hermaphrodites.

D. Kucharski K. Kucharska/Shutterstock.com

Earthworms possess both male and female body organs, making them simultaneous hermaphrodites. Their mating typically occurs when it has rained, and the ground is suitably wet. They are incapable of reproducing on their own and will require another worm’s assistance. 

Emerging from the underground, they extend their anterior ends and patiently wait for another worm to align in the same direction. Two worms pair with each other by establishing body contact from which a mucus-like substance is secreted into a ring around them. From there, they separate in a few hours and proceed to lay eggs that are fertilized in the cocoon. Usually, worms are ready to mate by the time they are 90 days old.

2. Earthworms have more than one heart

Earthworms don’t have a heart. They have ten pairs of pharyngeal arch arteries (five single-chambered aortic arches) that run across their bodies. They are counted as five hearts, mainly pumping blood and carrying food, waste, and respiratory gases throughout the earthworm’s body. Their hearts are not as complicated as ours—maybe because their blood doesn’t have to be pumped to many body parts.

3. Earthworms belong to the Animalia Kingdom

When mentioning earthworms, it is hard to automatically imagine them as animals. They belong to the Animalia Kingdom, though we often confuse them with insects. The fact that worms and insects come under the Animalia Kingdom does not mean worms are insects. 

In taxonomy, earthworms belong to the phylum Annelida, or segmented invertebrates. Members of this classification include aquatic worms, leeches, and other terrestrial worms. Worms of the phylum Nematoda, such as hookworms, roundworms, and threadworms, are usually cylindrical.

4. Earthworms do not have eyes or legs

Earthworms don’t have eyes. Instead, they depend on their receptor cells located on their skin. These receptor cells are highly sensitive to light and touch. They have a hydrostatic skeleton and a sleek body that is well streamlined. This adaptation enables them to squeeze into very tight spaces.

Earthworms don’t have limbs either. They have well-developed, powerful longitudinal and circular muscles wrapped around every body segment that help them push their way into the soil by wriggling and writhing. The setae also help worms grip the ground as they move.

5. Charles Darwin spent most of his years studying earthworms

earthworm digging into soil
Earthworms have a basic brain connected to their muscles and epidermis by nerves.

iStock.com/Christian Dahlhaus

Charles Darwin, the father of evolution, spent over thirty years studying earthworms and published his results afterward. In the book titled “The Formation, Vegetable Mold, and Action of Worms,” Darwin shared the results of his findings on earthworms’ diet, intelligence, and lack of ability to hear and respond to sound. 

Earthworms do not have ears, but Darwin tested their sense of hearing. He noted that earthworms behaved the same regardless of their continent and couldn’t hear sound but were responsive to vibration. Earthworms have a basic brain connected to their muscles and epidermis by nerves. The nerves detect any vibrations or flavors within the earthworm’s habitat.

6. Earthworms have no lungs or nose

That’s right; worms don’t have lungs or noses. So, how do they breathe? Earthworms, like all animals, need oxygen but can’t breathe through their mouths. Instead, earthworms breathe through their thin, permeable skin. They rely on diffusion to inhale and exhale, so the earthworm’s skin must always be moist for dissolved oxygen to pass into their bloodstream. They usually keep their skin moist by secreting slimy mucus. Worms can hardly survive in an environment that’s completely dry.

7. Earthworms die or get paralyzed if exposed to sunlight for a long time

Their skin contains several bio-molecules called sterol and tetraene, like humans. The effect of sunlight on earthworms degenerates circular and longitudinal muscles, thus drying the skin. Earthworms would be unable to breathe if the skin became too dry, and they would die. Earthworms do best in moderate conditions, which is why vermicomposting is a perfect solution for indoor composting.

8. Earthworms have an average lifespan of 4-8 years

red worms coming up out of the ground
Earthworms live for approximately 4-8 years.

iStock.com/Mik122

Earthworms live for approximately 4-8 years, though most garden worms do not exceed four years. They are constantly preyed on by many species of birds (starlings, crows, thrushes, robins, and gulls), toads, snakes, and numerous invertebrates (e.g., ground beetles, spiders, slugs, ants, and flatworms).

Earthworms dying inside the vermicompost systems can be traced back to a few problems, including lack of air circulation, extreme temperatures, incorrect moisture levels, and too much or too little food.

9. The Microchaetus rappi is the longest earthworm

Macrochaetus rappi takes the record for the longest earthworm specimen ever found. It was discovered in 1976 on the road between King Williams Town and Alice in South Africa and was 21 feet long (6.4 m) when extended. 

Other large earthworms include the giant Gippsland, with an average length of 3-5 ft (80-150 cm), though some specimens of about 6.6 ft have been recorded. The Oregon giant earthworm, native to North America, is also large and can grow to a length of 4.3 ft.

10. Earthworms are prone to protein poisoning

Protein poisoning is inevitable in earthworms. It’s caused by impaired protein digestion, which encourages fermentation, producing greater quantities of acidic compounds. Their calciferous glands can not excrete adequate calcium to neutralize acidity. Therefore, the gas build-up in the earthworms may lead to the rapture of their intestines, leaving them deformed. 

Earthworm in soil.
Earthworm in soil.
iStock.com/K-Kucharska_D-Kucharski
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About the Author

I hold seven years of professional experience in the content world, focusing on real estate, nature, and wildlife. Asides from writing, I enjoy surfing the internet and listening to music.

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