Question: Do earthworms really eat dirt?
Answer:
Yes, earthworms eat dirt.
But most of the dirt eaten by earthworms moves through their body and is deposited as waste. The waste of earthworms is called casts. There is much more to the earthworm’s digestive system than just eating and pooping dirt.
An earthworm’s digestive system consists of a mouth, a pharynx, an esophagus, a crop, a gizzard and an intestine.
- mouth The first section of the earthworm, the anterior end or head, consists of the mouth and the prostomium, a lobe which serves as a covering for the mouth and as a wedge to force open cracks in the soil into which the earthworm may crawl.
- pharynx Food particles pass from the worm’s mouth to its pharynx where the food is lubricated by mucus secretions. The food is very slimy now, which makes it easier to pass along to the esophagus.
- esophagus This is where the slimy food is mixed with calcium carbonate. Calcium carbonate is the same kind of chemical found in medication, such as TUMS, which is used for heartburn. Calcium carbonate is a base, which is a type of chemical that neutralize acids. Decaying food (a worms favorite food) forms acids but the calcium carbonate neutralizes this acid.
- crop Food passes from the esophagus to the crop, which is a temporary food storage area. In the crop the food gets mixed together. This mixture then moves into the gizzard.
- gizzard Earthworms do not have teeth to grind their food, but the muscles of their gizzard churns and mixes the food. Since earthworms eat dirt, the sand grains grind against the food tearing it into smaller and smaller parts. Glands in the walls of the gizzard add enzymes, which are chemicals that aid in the breakdown of chemicals in the food. When the food has been churned and mixed so that it looks like thick paste, it is moved in the intestine.
- intestine The thick paste of food continues to be digested in the intestine, where there are friendly bacteria that eat the food mixture. As the bacteria digest the food, the bacteria use what it needs and the rest is waster for the bacteria. This waste contains the nutrients that the earthworm’s body needs. A very important job of these friendly bacteria is that they prepare the nutrients in a form that can be absorbed into the small blood vessels lining the intestine. The blood carries the nutrients to all parts of the earthworm’s body.
- anus The worm’s intestine basically runs the length of the worm’s body. At the worm’s rear end the intestine ends. The end of the intestine, called the anus, is open and it is here where waste is excreted from the worm’s body. The waste pellets are called casts, which are mainly ground up soil. Dirt or poor soil might be eaten by the earthworm, but as it passes through the worm’s body it becomes it has become enriched with nutrients as well as acid neutralized. Dirt is changed to rich soil. Worms and their digestion help to fertilize the soil and grow our food!