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By Swati Singh
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Updated on 22 Apr 2025, 11:49 IST
Earthworms are fascinating creatures that play an important role in maintaining soil health. They belong to the phylum Annelida, meaning they are segmented worms. Earthworms are found all over the world, especially in moist soils rich in organic matter. Their simple but highly efficient body structure helps them survive underground, where they help in aerating the soil and decomposing organic waste. In this article, we will explore the morphology (outer structure) and anatomy (internal structure) of earthworms in simple words.
Earthworms have a soft, long, cylindrical body that looks like a tube. Their body is divided into many small rings called segments or metameres. An earthworm typically has around 100 to 120 segments.
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The earthworm's body has three important parts:
The body has two ends:
Earthworms move by contracting and relaxing their muscles. They also have tiny bristle-like structures called setae on each segment (except the first, last, and clitellum). Setae help in gripping the soil as the worm moves forward or backward.
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Now, let us dive into the internal structure of earthworms. Although they look simple from the outside, their internal body is well-organized and efficient.
Earthworms have a complete digestive system, meaning they have a separate mouth and anus.
Earthworms feed mainly on decaying plant material, and their digestive activity enriches the soil with nutrients.
Earthworms have a closed circulatory system, meaning blood flows through blood vessels.
Their blood contains hemoglobin, dissolved directly in the plasma, which helps carry oxygen.
Earthworms do not have lungs. Instead, they breathe through their skin.
Earthworms have a simple but efficient nervous system.
Earthworms can sense light, touch, vibrations, and chemicals even though they do not have eyes or ears.
Earthworms get rid of waste materials through structures called nephridia.
Their excretion helps maintain the water and salt balance in their body.
Earthworms are hermaphrodites, meaning each worm has both male and female reproductive organs.
However, self-fertilization is rare. Usually, two earthworms exchange sperm with each other during mating.
After mating, the clitellum secretes a cocoon, and the fertilized eggs are deposited inside it. After some time, small young worms hatch from the cocoon.
Understanding the structure and function of earthworms helps us appreciate their role in the environment:
Farmers often call them “friends of the farmer” because of their role in maintaining soil health.
Earthworms may look simple, but their body design is perfect for the underground life they lead. From their segmented bodies, moist skin, and simple nervous system to their efficient digestion and reproduction, every part of an earthworm's morphology and anatomy is well-adapted for survival. They play a silent yet vital role in maintaining the balance of nature. Understanding them better reminds us that even the smallest creatures have big impacts on our world.
An earthworm has a long, soft, and cylindrical body. It is divided into many small rings called segments. The body is moist, slimy, and reddish-brown in color.
The clitellum is a thick, band-like structure found around segments 14 to 16. It helps in reproduction by producing mucus that forms a cocoon to hold the eggs after fertilization.
Earthworms move by using their muscles and tiny bristles called setae. The setae grip the soil, and the muscles contract and relax to help the worm crawl forward or backward.
Earthworms breathe through their moist skin. Oxygen from the air dissolves in the skin and moves into their blood vessels, while carbon dioxide moves out.
No, earthworms do not have eyes or ears. However, they can sense light, touch, vibrations, and chemicals with the help of special cells in their skin.
Earthworms have a closed circulatory system, meaning their blood flows inside blood vessels. They also have five pairs of simple hearts to pump the blood.
Earthworms are hermaphrodites, meaning each worm has both male and female reproductive organs. During mating, two earthworms exchange sperm. Later, the clitellum forms a cocoon where fertilization happens.
The gizzard is a muscular organ that grinds the food into smaller pieces. It helps the earthworm digest soil and organic matter easily.
Nephridia are small organs that remove waste from an earthworm's body. They work like kidneys, helping the worm maintain its water and salt balance.
Earthworms improve soil quality by loosening it, adding nutrients, and helping plants grow better. Their activities make the soil healthier and more fertile, which is why farmers love them.
The prostomium is a small, lobe-like structure at the very front of the earthworm. It helps the worm feel the soil and directs food into the mouth.
The mouth of an earthworm is located on the first segment called the peristomium, just behind the prostomium.
The typhlosole is a fold in the wall of the intestine. It increases the surface area for better absorption of nutrients from the digested food.
No, earthworms need moist soil to survive. If their skin dries out, they cannot breathe properly and may die.
Bilateral symmetry means that if you cut the earthworm’s body from head to tail, the left and right sides will look almost the same — like mirror images.