How Much Worm Is a Worm?
AbstractWorms are slimy, wiggly, and gross. But did you know that they have many unique abilities? One of the neatest things that worms can do is regenerate, or re-grow, parts of their body. After a piece of a worm is cut off, it can grow back with all of the necessary new parts. How much of a worm can you cut off and still get regeneration? Is one end of the worm better at regenerating than the other? See if you can make heads or tails of this wiggly problem!
Sara Agee, Ph.D., Science Buddies
ObjectiveIn this experiment you will investigate worm anatomy and regeneration to find out how much of a worm can be left to regenerate a new worm or if one end is better at regenerating than the other.
Worms are one of the most overlooked biologically important animals. We are most familiar with worms we find while digging up dirt in our back yard. Worms do a lot of the planets dirty work, and are vitally important to decomposing and returning important nutrients to the soil. In addition to terrestrial, (land-living) worms, there are many other kinds of worms who live in water called aquatic worms. These aquatic worms are important in habitats like streams, lakes, seas, and oceans.
Worms are part of a group of animals called annelids. Annelids come in many shapes and forms, but share many common characteristics. They have segmented bodies with a left and right side, with a front end and back end. They are soft bodied, and do not have a skeleton. They secrete mucus, which is why they are so slimy, and have many muscles that make them very wiggly!
One of the neat things that worms can do with their bodies is regenerate, or re-grow, parts of their body that they have lost. This comes in handy when an earthworm has an unfortunate run in with your garden shovel or a hungry robin! If a part of the worm gets cut off, the pieces left behind will grow new parts.
Scientists who study regeneration try to understand how the process is regulated, and how the body of the worm turns regeneration on and off. How does a worm know when to start regenerating? When does is stop? How much of a worm can be left to regenerate, or will small pieces of worm die and fail to regenerate? Is one end of the worm better at regenerating than the other?
In this experiment you will cut worms in different places and in different sized pieces to find out if there is a relationship between regeneration and size or orientation of the body.
Terms and ConceptsTo do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!
- body length
- 2000. "Yucky Lab Activities: Worm World." Discovery Communications, Inc. Silver Spring, MD. 12/28/05.
- Day, Leslie. 1996. "The City Naturalist—Earthworms." The 79th Street Boat Basin Flora and Fauna Society. New York, NY.
- Appelhof, Mary. 1997. Worms Eat My Garbage: How to Set Up & Maintain a Worm Composting System. Flower Press. Kalamazoo, MI.
Materials and Equipment
- 16 oz. plastic party cups
- rubber bands
- Saran wrap
- moist soil compost
- water mister or spray bottle, available from Carolina Biological, item #: 665565
- permanent marker (Sharpie)
- earthworms, available from a local bait shop or nursery, from online suppliers such as Carolina Biological, item #: 141620, or
- Use a small hand trowel or shovel to dig up earthworms from the ground (they may be most easily found in shady, moist soil), or find them on the ground after it has rained.
- Note: Keep your earthworms in a cool place in damp soil and dead leaves until you are ready to test.
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- Prepare 4 cups for the earthworms to live in by placing 1/2 cup of moist compost into the bottom of each cup.
- Choose 3 worms of good size and equal lengths. Try to use large worms about 5 inches in length. The front end of the worm will be closest to the clitellum, the smooth band about 30 segments in from the end of the worm.
- Label the first cup, "control," and place one whole worm into the cup.
- Using scissors, cut your second worm in half and place the two pieces of worm into two cups labeled, "front half" and "back half."
- Using scissors cut the third worm into a one-thirds piece and a two-thirds piece. Place the two pieces into separate cups with corresponding labels.
- Cover the cups with saran wrap and secure to the tops of the cups with a rubber band.
- Using a toothpick, poke several small air holes into the saran wrap covering each cup.
- Keep your cups in a cool dark place for several days. Every three days, take out your cups and make observations of your worms.
- To observe a worm, get a paper plate and dump out the contents of your cup onto the plate. Find the worm, or piece of worm, and separate from the soil. Make observations of the worm, and return to the cup. Place 1/2 cup of fresh moist compost into the cup. Cover with the saran wrap and rubber band. Return to a cool dark place for three more days.
- Continue to observe your worms every 3 days for 2–3 weeks. Make drawings of the worms and write down your observations in a notebook. What do you notice?
- Summarize your data in a table. What trends did you see? Did all of the pieces survive and regenerate?
Ask an Expert
- Try different soil conditions for an effect on regeneration. Cut several worms in half and place into different types of soil: clay, sand, compost, manure, loam, bark, etc. Which soil conditions were best for regeneration?
- Earthworms can be used to break down materials in the soil. Many people place kitchen scraps in a worm box so that the worms will consume the material and turn it into soil. Will a regenerating worm still eat? Try placing kitchen scraps into containers of whole or regenerating worms. Which ones consume the most material?
- Earthworms are one type of "bioindicator" for healthy soil, which means that the number of worms can be counted and used to measure the quality of the soil. Poor soils have very low numbers of earthworms, and are not good for growing crops. Good quality soil contains many earthworms, and makes excellent rich soil for growing healthy crops. Dig up soil samples from different areas in your yard and count the numbers of earthworms present. Is your soil healthy?
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