Earthworm, the Ecosystem Engineers

Planet Earth is the most beautiful planet in the solar system. Life is flourishing only in this planet because of sunlight, water, huge variety of plants, different classes of animals ranging from unicellular amoebae to multicellular mammals. Earth has atmosphere that contains oxygen gas, required by all living beings for breathing.

Our planet has a rich biological diversity. It houses several thousands of birds, millions of flowering plants, lakhs and lakhs of marine and aquatic animals and plants and so on. There are many millions of different species of animals, birds, snakes, fishes, worms and plants living on this Earth. This biological diversity brings stability to the planet Earth.

Earthworm, belonging to the phylum annelids is one of the members in this bio diversity comes under animal kingdom and it is an invertebrate. It is found all over the world except in the Arctic and Antarctic polar regions. They are long, tube shaped, segmented worms. They live in the soil. The segmented body help them to live in burrows in soil. They feed on dead and decayed organic matter and soil.

They have no eyes. But they have light sensitive cells scattered in their outer skin. These light sensitive cells give their skin capacity to detect light and help the worm to identify changes in light intensity. The worm cannot see images like how we see images. Their skin is sensitive to touch.

Earthworm has no bones. The worm moves by contracting and relaxing its body segments. They have bristle like structure called setae that help the body to anchor and control the worm while moving through soil.

They have no lungs. They breathe oxygen from the air. Oxygen diffuses through skin into their bodies as their skin is permeable and skin is their respiratory organ. They have closed blood circulatory system. They have 5 hearts. The hearts manage excess calcium in their diet. The digestive system comprises of alimentary canal. It runs through the body.

The worm has two distinct ends. The anterior end and the posterior end. Mouth is situated at the anterior end and anus is at the posterior end. Large number of chemo receptors are concentrated near the mouth. They have the ability to regenerate the last segments.

They have simple brain which directs the worm in response to light. They have both central nervous system and peripheral nervous system. The worm is hermaphrodite. That is each worm carries both male and the female reproductive organs in their body.

Earthworm is called the friend of the farmer. 

Earthworm is a terrestrial organism. They live in borrows of the moist soil, rich in dead and decaying organic matter or humus. It is nocturnal animal. Earthworm comes out of the burrows during night time in search of food, which is dead and decayed organic matter.

When earthworm moves through the soil, it keeps on turning the soil in such a way that upper layer of the soil goes down and the lower layer of the soil comes up.  So soil layers are loosened and aerated. It feeds on the soil and the organic matter present in the soil. It digests the soil and the organic matter and excretes the same. The excreta of the earthworm is very soft to touch. This type of activity of the earthworm helps water to reach the roots of the plants easily. Air can penetrate into the soil and soil will absorb oxygen from the air.

The undigested matter of earthworm is the excreta of the animal comes out of anus. It is rich in urea and hence rich in nitrogen. The excreta makes the soil fertile. The dead worm also increases the nitrogen content of the soil. Therefore earthworm is called the friend of the farmer.

The burrowing and feeding activity of earthworms are very beneficial to soil quality and crop production. Roots of the plants need oxygen for their growth and give out carbon dioxide through soil. As earthworm keeps on ploughing the soil, its porosity improves the exchange of gases with the atmosphere. This help the plants to grow well.

The worm castings have higher nitrogen, phosphorus, calcium and potassium content than the surrounding soil. This excreta contains many beneficial microbes that help decompose crop residue and this increases the nitrogen content of the soil.

As the earthworm moves in the soil, it ploughs the soil turning the layers of the soil upside down. It mixes the various layers of the soil nicely. This helps water to penetrate deeply into the soil. The impurities present in water are filtered by the soil. Thus earthworms improve the soil structure and they open up the space in the soil structure called pores.

Earthworms modify the soil properties. The physical, chemical and biological properties of soil are modified by the earthworms due to their burrowing activity. This modification of soil profile will influence the habitats and activities of other organisms within the soil ecosystem.

Earthworms are economically important. They are used as baits for fishing in many parts of the world. They are used as food by a large number of animals like frogs, moles, lizards, small insects etc. The earthworm makes the best food for fish in an aquarium and small animals in the laboratory. The Ayurvedic and Unani system of medicine suggests that earthworms are used for curing obesity, removing bladder stones, curing jaundice, and piles etc.

Earthworm's habit of burrowing makes the soil loose and porous. Their burrows permit the penetration of air and moisture in the porous soil. The faeces of earthworm is a good manure. The secretions of worm enrich the soil by adding nitrogenous bases. This idea is made use of in making vermicomposting. Vermicomposting is making use of earthworms for composting organic residues. Vermicomposting can be done at home also on a small scale.  By vermicomposting we are preserving the earthworm species and in this way we can farm earthworms.

Earthworms, along with bacteria and fungi, decompose organic material. They increase the nutrient content of the soil. They improve the soil structure by burrowing. Burrowing also improves soil aeration and enhances plant root penetration. They are members of the food web. Birds and snails are their predators.

The earthworms play a vital role in our biodiversity. They live in the soil, eat the soil, digest the soil, plough the soil and enrich the soil. Thus they protect our soil by adding nutritive values to it. If the soil is preserved this way by the earthworms, water and air that touch the soil are also purified and preserved. Thus the earthworms help in preserving our environment. Undoubtedly, they are the “engineers of our ecosystem”.