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Earthworms, Christmas Tree Worms, Leeches, and Other Annelids

Earthworm

Earthworm

Annelids are segmented worms, like earthworms and leeches.

Annelids (animals belonging to the Annelid Phylum which is in the Animalia Kingdom) are segmented worms including earthworms, leeches, fireworms, Christmas Tree worms, and many other species. Having segments is one of the primary characteristics that separates annelid worms from flatworms and roundworms. These segments are rings that repeat all up and down the worm's body.


Most annelids live in the ocean, but others, like the earthworm, live on land. You may be surprised when you see some of the photos of the marine annelids below - as they just don't look like worms at all! Have you ever seen a Feather Duster worm?!


Characteristics of Annelids - Segments, coelom, bristles, closed circulatory system, and more

Nereis - A segmented worm in the Annelid Phylum.

Nereis - A segmented worm in the Annelid Phylum.

  • Segmentation - Each segment in a segmented worm contains many of the same organs, including those used in digestion, movement, excretion (getting rid of waste), and circulation. In the photo above, you can easily see the individual segments of the worm.
  • Septa - Septa are internal walls that separate the body segments. They can be found in most types of annelids. The worm's circulatory system allows nutrients and other things to be passed from one segment to another.
  • Cerebral ganglion - A cerebral ganglion is a primitive brain that is located in a segment near the front of the worm.
  • A nerve cord connected to the brain runs along the underside of an annelid's body. This nerve cord carries sensory information from the various segments to the worm's brain.
  • Coelom - A coelom is a fluid filled cavity located between the gut and the body wall. The coelom of an annelid is a true coelom because it's located entirely within the mesoderm (muscle tissue). For more about the coelom, please visit: The Types of Bodies Animals Have.
Coelom

Coelom

  • Closed circulatory system - Like humans, annelids have a closed circulatory system. That means that the blood pumped by the heart is fully contained within the circulatory system and does not wash out into the tissues of the body.
  • Annelids have highly specialized organs.
  • Nephridia are excretory organs which remove wastes from the annelid's body.
  • Setae are bristles that are located on each segment of some annelids. Setae help increase traction to make movement easier for the worm.
  • Parapodiaare almost like a series of little feet. Parapodia are paired and unjointed appendages (things that stick out from the main part of the body are called appendages.). Some, but not all, annelids have parapodia.


Did you know that annelids can be anywhere from 1 mm (.04 inches) long to over 3 meters (10 feet) long?! A 3 meter long worm?! Wow!Check out the video below on "Giant Earthworms!"

Giant Earthworms

There's a lot of variety to the worms that make up the Annelid phylum!

What? These are all worms??

Yes. These are segmented worms in the annelid phylum.

Feather Duster Worm

Feather Duster Worm

Feather Duster Worm

Christmas Tree Worm

Christmas Tree Worm

Christmas Tree Worm

More Christmas Tree Worms

More Christmas Tree Worms

More Christmas Tree Worms

Earthworm

Leech

Leech

Leech

Fireworm

Fireworm

Fireworm

Good Worms, Bad Worms

Leeches

Leeches are a "blood sucking" type of annelid

Leeches are different from many annelids in that they do not have bristles (setae). Also, the external segmentation of their bodies does not match up with the internal segmentation of their organs. Because there is not much empty space in their coeloms, the bodies of leaches are much more solid than those of most annelids.

Leeches can live in water (fresh water or marine) or on land.

Another characteristic of leeches is that they have two suckers, one one each end of their bodies. Leaches use these suckers to get blood from other animals.

Leeches are sometimes used for medical purposes. The video below explains more about how leaches are used to help people get well.

Did you know?

Did you know that leeches have a substance in their salvia called hirudin which helps prevent the blood of their "victim" from clotting?

Leeches Cure

Earthworms are a type of annelid - The characteristics of earthworms

earthworms-leeches-annelids
  • No parapodia (Parapodia are the feet-like appendages on the sides of some annelids.)
  • Only a few setae per body segment. (Setae = bristles.)
  • Earthworms do not have eyes, but they can sense light. Earthworms do not like light and will move away from it when possible.
  • Earthworms can eat their weight in soil every day!
  • The soil earthworms eat goes from the mouth into the esophagus (throat) and then into the worm's crop. A crop is a "storage room." Next the soil moves into the gizzard of the worm. After the soil is broken down by a grinding action in the gizzard, it moves into the intestine. Here, some of the digested food is absorbed into the intestinal wall, while the rest moves on out of the body via the anus, forming castings.
  • The skin of earthworms must remain moist, or the earthworms will die. This is because oxygen and carbon dioxide can only pass through an earthworm's skin if the skin is moist.
  • Earthworms are hermaphrodites which means that each earthworm contains both male and female reproductive organs. To mate, earthworms join at their clitella (located about a third of a way down mature earthworms) and exchange sperm. Both worms then form an egg capsule which is shed after about 7 to 10 days in their castings. 14 to 21 days later, baby worms hatch. Each egg may contain between 1 to 5 baby earthworms! It takes between 60 and 90 days for the baby earthworms to become adults.

Earthworm Dissection

Observing Live Worms Is An Excellent Way To Learn More About Them! - Worm Composting

Worm Composting invovles preparing some sort of box (with air holes that are small enough the worms can't escape) for the worms to live in. You feed the worms scraps of vegetable peels, etc, and as they eat the food scrapes, they turn the scraps into wonderful compost you can use in your garden! Worm composting is a great way to learn more about worms!

The kids in our homeschool co-op did worm composting as a project one year. They uses plastic tubs with lids. One of the parents drilled tiny holes in the tubs, so the worms could breath. For more info, please refer to one of the books below, or visit: Worm Composting Basics.

Let's see what you've learned about earthworms!

For each question, choose the best answer. The answer key is below.

  1. If you cut a worm into 4 pieces, will you get four new worms?
    • Yes
    • No, you'll have a dead earthworm who's now in 4 pieces!
    • No, but you might end up with one live earthworm if the cut was made after the section with the important organs.
  2. Earthworms are in the phylum:
    • Porifera
    • Cnidaria
    • Platyhelminthes
    • Mollusks
    • Annelida
  3. Why do earthworms crawl all over the street or sidewalk when it rains a lot?
    • Too much moisture will kill them, so they have to come out of the ground if there's too much water in the soil.
    • They love moisture and come out to get wet!
    • They are like groundhogs and like to come out of the ground to check on the weather!
  4. How do worms help our gardens?
    • Earthworm castings contain nitrogen and other nutrients plant need.
    • They till up the soil so the roots can get more air!
    • Both of the above.
    • None of the above.
  5. How do earthworms reproduce?
    • It takes a boy earthworm and a girl earthworm to make baby earthworms.
    • Worms don't have sexes, so it only takes one earthworm to make baby earthworms.
    • Worms don't have sexes, but it still takes two of them to make baby earthworms.
  6. Do earthworms have eyes?
    • No, all they know is total darkness.
    • No, but they can sense light anyway.
    • Yes, they have eyes.
  7. Earthworms are always smaller than a foot.
    • Yes. If they were any bigger, they'd be snakes.
    • Yes, earthworms stay small so they can dig in the dirt.
    • No, some earthworms can grow to be 10 feet long!
  8. How do earthworms move?
    • By contracting and elongating their bodies, over and over.
    • They slide along smoothly.
    • They have tiny feet with move them along.
  9. What type of circulatory system does an earthworm have?
    • open
    • closed
  10. Do earthworms have a brain?
    • Nope.
    • Yes, a primitive one.
    • Yes, they have a complicated brain.

Answer Key

  1. No, but you might end up with one live earthworm if the cut was made after the section with the important organs.
  2. Annelida
  3. Too much moisture will kill them, so they have to come out of the ground if there's too much water in the soil.
  4. Both of the above.
  5. Worms don't have sexes, but it still takes two of them to make baby earthworms.
  6. No, but they can sense light anyway.
  7. No, some earthworms can grow to be 10 feet long!
  8. By contracting and elongating their bodies, over and over.
  9. closed
  10. Yes, a primitive one.

Interpreting Your Score

If you got 9 correct answers: B. Well done. You got most of them correct!

If you got 10 correct answers: A+ You really know your worms!

Earthworms

An Earthworm's Life

Biology

A list of webpages in this biology series

Homepage: Biology: Information, Videos, and Labs

Unit 1 on Cell Biology

Biology Labs, Activities, Videos, and Study Guides About Cells (Photosynthesis, Mitosis, Cell Organelles, and More)

Unit 2 on Genetics

Labs, Information, And Videos For High School Students Studying Genetics.

Unit 3 on The History of Life on Earth

The History Of Life On Earth.

Unit 4 on Ecology

Ecological Principles / Populations

Ecosystems

Biological Communities - Symbiosis, Niches, and Biomes

Global Changes And The Environment

Unit 5 on Diversity

An Introduction to Taxonomy - The Kingdoms and Domains Of Life

Learning About Viruses And Bacteria

Protists: Paramecium, Amoebas, Algae, Diatoms, Euglena, and Others

The Fungi Kingdom

Unit 6 on All About Plants

The Plant Kingdom

Unit 7 on The Animal Kingdom: Invertebrates

The Animal Kingdom - An Introduction

Sponges are Simple Animals

The Cnidarians: Jellyfish, Sea Anemones, Hydrozoans, and Corals

Earthworms, Christmas Tree Worms, Leeches, and Other Annelids

Mollusks Are Invertebrates

Unit 8 on Vertebrates

NEW! Fish: The Characteristics of Jawless Fish, Cartilaginous Fish, and Bony Fish

Check back later for additional biology units!

Were you surprised that some of these species are called worms? Which one is your favorite?

© 2012 JanieceTobey

"Earthworms, Christmas Tree Worms, Leeches, and Other Annelids" Guestbook - Comments? Questions? I'd love to hear from you!

BigsteveC on January 09, 2013:

is the nereis the worm we refer to as the clam work? - they don't look too appetizing to me but striped bass sure love them

Laura45 LM on January 09, 2013:

Very interesting!

JanieceTobey (author) on December 20, 2012:

@Bill Armstrong: LOL, Bill! Don't you use my pretty Christmas tree worms for fish bait! ;-) Enjoy your holidays!

Bill Armstrong from Valencia, California on December 20, 2012:

Yea some nice fish bait here ;)

AlleyCatLane on June 19, 2012:

You have shown some surprisingly beautiful worms. Had no idea they came in so many different forms.

BestRatedStuff on May 14, 2012:

Enjoyed that, leaned a lot about an animal that I always found fascinating. And as Tipi said "you are a teacher's teacher for sure"

anonymous on March 11, 2012:

Janiece, you are a teacher's teacher for sure...I'm just a student and was able to get 100% on your quiz after reading your fabulous worm facts and showing me worms I didn't even know existed, excellent as usual and blessed.

Anthony Godinho from Ontario, Canada on March 09, 2012:

Those Christmas Tree worms looks beautiful. Looking at those earthworms took me back when I was a kid in school. Stay blessed! :)

anonymous on March 07, 2012:

Super cool and stunning imagery!

burntchestnut on March 06, 2012:

I don't like to touch worms, but they're fascinating. Nature is so interesting. I have a lens called "Maggots and Leeches Used For Wound Cleaning and Solving Crimes" and another one "Worm Poop | Worm Castings Are The Best Organic Fertilizer."

Barbara Radisavljevic from Templeton, CA on March 05, 2012:

I rather like the Christmas tree earthworms. I had no idea such worms existed. Why have I never seen any of these worms while digging in my garden except the earthworm

Terrie_Schultz on March 05, 2012:

Those Christmas tree worms are really cool!

Heather B on March 05, 2012:

Very enlightening. I will give our little wormy friends more consideration the next time I see one!

Marika from Cyprus on March 05, 2012:

Yay, not sure I like them, but great lens.

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