Being able to track down water bears

The roundworm, often known as the nematode, is one of the most abundant microscopic creatures on the planet. Roundworms make up four out of every five multicellular creatures on the earth. It's a tiny, wormlike creature that may be found almost anywhere. That includes your backyard as well.

What is needed:

• a little piece of moss;

• a small dish or any small waterproof container;

• a Petri dish;

• rainwater or distilled water (better not to use tap water);

• black paper;

• a pipette;

• a microscope (or a magnifying glass with a magnification of 10x);

• microscope slides and cover slips (three per microscope slide).

1. Placing the moss in water

   1. 1. Choose a piece of moss that fits in the Petri dish. Remove as much of the loose earth as possible. Do not be alarmed if a few of the larger inhabitants quickly run away.

   2. Put the moss upside-down in the dish and fill it with water until it is about one centimetre deep.

   3. After a while, the moss will have absorbed the water. Then add a little more.

   4. When the moss is really soaked with water, add a little more water until it is about half a centimetre deep.

   5. Now let the dish with the moss stand for at least three hours. Overnight is good as well.

2. Looking through the Petri dish

   1. Let the excess water flow out of the dish. Shake or squeeze the water out of the moss above another Petri dish.

   2. Place this second dish on the black paper or another black background and look at it with the microscope or with a magnifying glass.

   3. Search for water bears. At magnification of 10x they are still very small and their legs can hardly be seen, so they might look like thick little worms. But you can only see them from close up if they are lying on a microscope slide. Some types are red, most of the larger types are whitish or transparent. Sometimes water bears hold on to little pieces of dirt or little grains of soil and this makes them hard to see.

3. Making a specimen

   1. When you have found water bears, carefully suck them up in a drop of water using the pipette.

   2. Place the drop of water on a microscope slide.

   3. Put two coverslips on each side of the water drop, and then place a third coverslip on top of the water drop. Make sure that the two side cover slips are in between. This means there will be enough space between the microscope glass and the cover slip to prevent the water bears being accidentally squashed.

   4. Look at the water bears with 20x and 40x magnification.