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Inquiry into the Zen of Wormness

"They are not brethren, they are not underlings; they are other nations, caught like ourselves in the net of life and time, fellow prisoners of the splendor and travail of the Earth.

-- Henry Beston

Introduction: Worms make good tools for inquiry --- they are familiar yet still alien enough to invoke interest. Many people have dissected a worm in biology class but that is a far cry from getting to know a living worm up close and personally. As children, as well as adults, get caught up in our increasingly high-tech world, the reality of the world around us threatens to become lost. I think the point of this avenue of inquiry is to get people to appreciate the lives of other living things with which we share this Earth.

Worm Facts (or things to remember when you are about to impale a worm on your fish hook):

Earthworms in general

• have been around 120 million years. They evolved during the time of the dinosaurs; hominids have been around only about 4 million years and Homo Sapiens about 25O,OOO years.
• enrich and aerate the soil. Darwin found that worms turn over the top 6 inches of topsoil every 20 years.
• can grow to 11-feet-long -- this species lives in Australia.
• lack a brain but have nerve centers (called ganglia).
• lack eyes but can sense light with photoreceptors.
• are hermaphrodites (both sexes in one animal) but cross fertilize.

• are an exotic, alien species introduced from Europe in the soil around plant roots
• live 5-10 years
• can grow to a foot in length
• burrow to six feet or more
• have 5 "hearts"
• have red blood (with hemoglobin like us)

• a tray is nice but not absolutely necessary
• paper towels
• a spray bottle so that people can keep the worms moist.
• que-tips
• different chemicals (alcohol, vanilla extract, liquid smoke, etc.)
• dry sand
• soil
• a clear plastic tray so that you can shine a light from beneath the worm
• a flashlight
• magnifying glasses
• ice cubes

It helps for people to work in pairs. This way they can generate more questions and suggestions for testing hypotheses. To get things going, ask each one to introduce themselves to their worm partner. Ask them to think about where they look when they introduce themselves to other humans. They look at the face. Does a worm have a face? Indeed, does a worm have a head? They can begin their investigation into worm ways there. Your role is to circulate and move their inquiry along. When they ask questions try to get them to suggest ways that they could test to learn the answer. If they don't come up with questions, help them along by asking a question and having them testing for answers. Also keep in mind that different worms, like people, respond differently in the same situation. So, if two teams try the same experiment and get differing responses ask them what they would have to do to really verify their results. Lead them to the conclusion that repeatability is essential to making any firm conclusion and many trials need to be run before you can say anything is true with any certainty. Some questions that could come up are:

• Is there a top side and a bottom side? Tell them to think of a way to find out. Hopefully they will turn the worm over to see if it looks physically different (it does). Have them run a finger along the underside. They should feel the setae (stiff hairs) which the worm uses to anchor in the soil and help propel it along. Have them observe how the worm will right itself if overturned.
• Does the worm have a skeleton? Ask them what they think based on picking the worm up and gently feeling it. Go over how a skeleton helps us move by being an attachment site for our muscles. Ask them if they think a worm has muscles.
• If it doesn't have a skeleton how does it move? Have them observe how a worm moves and come up with a scheme of how the muscles work based on their observations. Worms have a hydrostatic skeleton, i.e. it is a bag of water. Contraction of circular muscles will extend the worm Contraction of longitudinal muscles will make the body contract.
• Does a worm prefer wet to dry areas? The fact that you start out with the worm on a wet towel seems to indicate this preference but ask the participants to test for their worm's preference. Just observing the worm as it comes to the edge of the wet paper towel should lead to some conclusion. Or a dry paper towel can be folded in half and placed on top of one half of the wet towel to see what happens.
• Does a worm eat? Lumbricus is a fairly thick worm but if you they can make it stretch out on a clear piece of plastic and shine a light up through the body, the digestive tube can be seen. A worm is essentially a tube within a tube. The mouth is a toothless opening on the underside of the "head's" first segment. The digestive system is a linear tube with an enlarged portion which can grind up leaves or other organic debris on which the worm feeds. The feces are called castings and serve to enrich the soil.
• Does a worm have babies? This is just informational. Unless it is spring you probably won't be able to observe mating. Worms are hamaphrodites, they are both male and female at one time. Why would this be a good situation? Because any worm encountering another worm will immediately know that it can mate with the other worm. They don't have to spend much time determining whether the other worm is of the same or different sex. Worms mate in the spring. The genital openings are anterior to the clitellum, that band near the front end that is enlarged and of a slightly different color. The worms exchange sperm simultaneously, separate, then a few days later the clitellum secretes a tough cocoon filled with albumin (like egg white) which picks up the eggs and sperm as it passes forward. The cocoon seals when it passes off the worm's head and fertilization takes place within the cocoon. Development takes place within the cocoon and the young hatch in 12-13 days.
• Do worms have soil type preferences? Have the participants come up with ways to test for this. For example put a ring of dry sand around the worm to see how it will react. When it appears not to like to cross over the sand ring ask why. Is it because it is "scratchy" and uncomfortable and sticks to the worm's skin? Can a worm find a break in the sand ring repeatedly? What does this tell you about the "cognitive" abilities of worms. How can you test to see if it is the discomfort of the sand the worm objects to or if it is the dryness? (Participants can wet the sand). Explore other types of soils.
• Worms live in the dark .Do they have eyes? How do they react to light? Worms don't have eyes like you or I have. But they do have photoreceptors that detect light. These are mostly concentrated in the anterior end. Have participants test to see if worms can detect light from dark. (Put a sheet of paper over one end of the tray and see if the worm can find it.). Or, often the worm will crawl under the wet paper towel, which in itself indicates it is seeking a darker space. Try sprinkling dark dirt in a winding path on top of the wet towel and see what happens. The worm will follow the trail of darkness stopping where the trail stops.
• What does a worm do in the winter? I.e., does a worm respond to cold? This is what the ice cubes are for, but have them available and let participants come up with a test. It can be as simple as putting a cube down on the papa towel and seeing if the worm will avoid the cube and cold melt water. After making predictions, and observing the worm's reactions have the participants suggest what a worm does in winter. Below the frost line the earth tends to stay at a constant temperature most of the winter. Worms just burrow deeper in winter.

Holley, Dennis. 1994. Animals Alive! An Ecological Guide to Animal Activities. Roberts Rinehart, NY.

Kneidel, Sally Stenhouse. 1993. Creepy Crawlies and the Scientific Method. Fulcrum Publ., Golden, CO.

Stevens, William K. 1995. It's Natives vs. Newcomers Down in the Worm World. New York Times, March 28.