Archive for April 9th, 2013

April 9, 2013

Backyard Connections: Snuggling Up to Soil’s Construction Crew

by Melissa Harding

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This new series, Backyard Connections, gives fun and easy tips for exploring the nature right outside your door.

Spring is the perfect time to get out and explore your yard. There is so much to see and do; plants are sending out new shoots, birds are nesting and the grass is turning green. In short, spring is a time of transformation and you don’t want to miss it! Start off my looking down at your feet and even farther into the ground; though it may look brown and lifeless, soil is truly alive. It is an ecosystem all of it own, complete with producers, decomposers and everything in between.  At Phipps, one of our favorite soil citizens is the humble worm. While it may just look like a slimy tube, a worm is so much more than that.

The earthworms that you see crawling in your flower garden contribute to soil health by adding nutrients through their castings and aerating the ground by digging tunnels. Worms eat soil; or rather, they consume the soil and digest bacteria from individual particles. They take giants bites of the soil as they crawl along, creating tunnels wherever they go. Whatever they don’t digest is excreted out the other end as worm castings. If these little guys didn’t fill the ground with tunnels, the soil would become compacted; this means that there would be no room for air and water in the soil, which would put the other critters and plants in bad shape. Worms are essentially the soil’s construction crew, making sure that everyone underground has a home.

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Worms are also one of the most interesting soil critters to study.  Grab a piece of newspaper, clear plastic lid, flashlight and spray bottle of water, because here are the steps to conducting a super fun worm study at home in your own backyard:

Look inside
Worms are transparent, which means that you can literally watch their organs working.  The best way to look inside a worm place it on a clear, plastic plate and shine a flashlight up through it. The worm won’t like this, but it won’t hurt it. Look for tube running down the middle of the worm, filled with dark granules. That is the digestive tract. Worms don’t have stomaches, but rather a crop and gizzard (like a bird). After it eat, it stores the food in a crop, which is a little sack. Its gizzard, which is another sack made full of stones the worm has swallowed, grinds the food down and passes it through the intestines where nutrients are absorbed. The dark granules are pieces of dirt that the worm has swallowed.

Another thing to look for are the five hearts; they are not shaped like human hearts, but rather are actually aortic arches. Worms have blood vessels that move blood through their bodies very close to the skin (which is why they look pink). Human hearts work with our lungs to pump air into our blood and blood through our bodies. Worms have no lungs, as they breathe through the skin, so what their hearts do instead is help them digest their food.

Heads or Tails?

If you try to look for a worm head, you may be a bit baffled. Worms do have a head and tail, but it can be hard to tell which end is which. Worms have no eyes, since they spend most of their time underground in the dark; instead, they sense vibrations in the soil. To find the head, you need to put your worm on the ground or on your plastic plate and then wait. The worm will start to crawl; the head will lead the body as it begins to move. This is the end with the mouth, or prostomium. This is hard to see with a magnifying glass. In fact, it can be hard to discern much of anything with your eyes. Your ears, however, can help you.

Put your worm on a small piece of newspaper and then bend your ear down to listen. You should hear little scratching noises; this is the sound of the worm’s setae against the paper. Setae are little bristles on the worm that help it move through the soil. If a worm wants to hold itself tight against the soil, it can jab its setae into the dirt. You can also feel them on the worm, like little bumps. Run your fingers down its underside; its feels smooth, you are moving towards the tail and it feels rough, you are moving towards the head.

Make a muscle

See those stripes on the outside of the worm? Those are muscles! Earthworms have no arms or legs. They have two sets of muscles; one that makes it long and the other one that makes it short. When they want to move, the earthworm will alternate the use of its long and short muscles, which allows its body to be pushed forward in the soil. These are great to find with a magnifying glass.

Egg Hunt

Look for a band in the middle of the worm. This is called the clitellum, which is where a worm lays its eggs. Worms are hermaphroditic, meaning they have both eggs and sperm inside of them. However, they still need to mate in order to preserve genetic diversity; two worms will join their clitella together and exchange sperm sacks. Each worm will use the other’s sperm to fertilize their own ovules, then they lay little yellow sacks of eggs. These egg sacks are very small, about the size of a pin head, so it can take some work to find one. If you do, you are in for a treat; look carefully and sometimes you can even see the embryo inside!

By this time, your worm is probably pretty tired. Make sure to put your new friend back someplace moist and dark – under a rock or a chuck of soil. It will find its own way back down under the ground.

A note on handling worms: worms are very sensitive to temperature, light and moisture. It is always important to handle them with moist hands and watch for signs of fatigue. They will start to stretch out and go limp; they’re not dead, but it is best to put them back and give them some time to rest in the dark.

If you enjoy studying the worms in your yard, grab a shovel and dig for more critters. Pill bugs, millipedes, centipedes, and ants are just a few of the organisms that you can find in a handful of dirt. Even better, get your magnifying glasses and explore the tiny hairs on plant roots and the white strands of mycelia scattered through the soil. There are over 1 million earthworms in an acre of soil, so get digging!

The top photo is copyrighted by Molly Steinwald; the bottom photo was taken by Christie Lawry.

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