How Does an Earthworm Eat?

Charles Darwin said of the earthworm, "It may be doubted if there are any other animals which have played such an important part in the history of the world as these lowly organized creatures." Indeed, the earthworm's contribution to the earth's ecology is as important as it gets. And for the segmented worm, it's really all about eating and excreting. According to the website Backyard Nature, for each acre of cultivated land, 16,000 lbs. of soil pass through earthworm gastrointestinal systems, resulting in a deposition of 30,000 pounds of worm-enhanced top soil!

  1. Anatomy

    • Earthworm anatomy is simple and sleek. These creatures are considered annelids, or segmented worms. They've evolved for living in narrow underground tunnels, which means no antennas, limbs or tails. Although earthworms have no eyes, they do have light-sensitive skin. The worm brain is so simple that it can be removed without ill effect. And this creature has not one but five hearts. As the worm breathes through permeable skin, it has no lungs. Earthworms are hermaphroditic, carrying both male and female reproductive parts.

    Digestive System

    • The earthworm's digestive system is made up of the mouth, pharynx, esophagus, crop, gizzard and intestine. The worm actually has lips, and very powerful ones at that. Given the creatures lack of limbs, the mouth must act somewhat like a hand. When the worm locates dead grass or leaf bits for consumption, the lips serve to break down the vegetation into small pieces. Worms have no teeth. Grains of soil take the place of teeth, helping them to masticate their food.

    From Mouth to Crop

    • Worms that live near the surface of the earth eat dead grass and fallen leaves, along with the microscopic algae and bacteria on these leaves. Worms deeper underground eat bacteria-infused raw dirt. The organic particles move from the worm's mouth to the pharynx, where mucus membranes lubricate the chewed vegetation. This makes for easier passage to the esophagus. Here, calcium carbonate is introduced to balance out the acids that are created. The food mixture is then housed in the crop before entering the gizzard, which is where digestion truly begins.

    The Gizzard

    • The earthworm's gizzard is made up of strong muscles that blend together the bulk of food and dirt. This blending action generates a thick paste. The walls of the gizzard harbor glands that produce digestive enzymes. These enzymes further aid in the breakdown of the organic matter---the thick paste---that will leave the earthworm's gizzard and move along to the intestine.

    The Intestine

    • Not unlike the human intestine, the earthworm's intestine has good bacteria that eats away at the organic material moving through it. In the process, the worm's body releases and absorbs nutrients.

      Soil particles and undigested leaves and grass pass through the anus and out of the earthworm's body. A worm cast is generated. Worm castings are potent sources of calcium, magnesium, nitrogen and phosphorus. These nutrients are essential to healthy, thriving ecosystems.