A short note on Earthworm

Earthworms are generally found in humid and muddy fields. You see them burrowing through the soil and often people feel disgusted by them. Its scientific name is Lumbricus terrestris and it is very helpful for our ecology. Earthworms help us fix the soil fertility and increase crop yield. The worm dangling at the end of a fishing rod is also an earthworm. Let us see how they matter so much in the ecology.

Earthworm: brief about the creature

Biologically classified under the animal kingdom and the phylum of annelida, the scientific name for an earthworm is Lumbricus terrestris. They occur all over the world and are generally found in muddy soils or humid climates.  

An earthworm is an invertebrate, meaning it does not have a vertebra. This means it lacks a skeleton but the body structure is maintained by a skeleton that is supported by fluid pressure or a hydrostatic skeleton. Its body is long and tube-like and bears segments; both on the inside and outside. They thrive on organic matter, hence being its primary food. 

The digestive system of an earthworm lies throughout the length of its body and the respiratory organ for an earthworm is its skin. Earthworms are hermaphrodites which means that the male and female reproductive organs lie in the same body. When they mate, two earthworms exchange sperm and fertilise the eggs of the other. 

Anatomy

The typical length of an earthworm is around 10 mm to 3 metres and approximately 25 mm. The whole body is shaped like a cylinder.

Pores which are too fine to be seen by the naked eye are present throughout to allow the earthworm to respire. 

Segments are seen externally and some of those sections are present inside too. Some setae are used as anchors to lodge into the soil or even penetrate into the partner’s body during mating. 

An adult earthworm has a swelling called the clitellum, which is often used to store the eggs that are produced after the mating process. 

On the outside, the earthworm is surrounded by a thin layer of cuticle which helps the earthworm’s skin to be moist and allows it to easily burrow into the soil.

Ecological importance

Earthworms are often called the farmer’s friends. There is a reason for this. Earthworms help in breaking down organic particles like dead leaves, animals to organic manure and this in turn replenishes the soil with rich nutrients which increases overall soil fertility. 

The earthworm also breaks down small particles like sand and soil, which again help in increasing the fertility of soil. The earthworm leaves behind casts of its body which are very rich in nitrogen and phosphates. This balances out the lost nutrients in the soil.

The burrowing motion of the earthworm creates channels in the soil which allows air and water to pass through to the deepest layers of soil. Not only does it improve aeration in the soil, it also brings an improvement in the drainage of soil. This burrowing motion also again adds nutrients to the soil in the form of body casts that are left deeper in hence increasing nutrient uptake in the plant.

Due to these reasons earthworms are used widely in vermicomposting and when projects related to soil restoration are taken. They prepare the soil to grow natural plants especially when there has been an attack of an invasive species.

They are also used as fish bait and help humans increase fishing yield.

Earthworms as an invasive species

Even though earthworms help increase the nitrogen content in the soil, too many in a small area release too much nitrogen which makes the soil acidic. This disrupts the natural pH and hence can be harmful to growing crops. The natural pH required for Lumbricus terrestris is that of 5.4. 

Even though there is no conclusive proof yet, scientists believe that they might be adding to the global warming emissions.

Conclusion

In the previous sections we saw what an earthworm is like and their most astonishing feature is that they breathe through their skin! An earthworm is really important in our fields as well for vermicomposting. Let us hope farmers realise their worth and actually use them for increased yield.