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This video will help you to learn What are the features of the earthworm?
Do you think earthworms are cool creatures that are fun to play with ??
Or are they icky, creepy, slimy, crawlies that you’d rather avoid.
But these earthworms are farmers' best friends because of the multitude of services they provide that improve soil fertility and consequently plant health.
The earthworm is a reddish-brown terrestrial invertebrate that inhabits the upper layer of the moist soil.
The common Indian earthworms are Pheretima and Lumbricus.
Let’s learn about the morphology and anatomy of an earthworm.
Earthworms have a long cylindrical body.
The body is divided into more than a hundred short segments which are similar and called metamers which are about 100 to 120 in number.
The dorsal surface of the body is marked by a dark median mid-dorsal line.
While the ventral surface is distinguished by the presence of a genital opening.
The first body segment of an earthworm is called the peristomium or buccal segment which contains the mouth.
In a mature earthworm, segments 14 to16 are covered by a prominent dark band of glandular tissue called the clitellum.
This dark band makes the body is divisible into three prominent regions – pre-clitellar, clitellar and post-clitellar segments.
Four pairs of spermathecal apertures are situated on the ventrolateral sides of the intersegmental grooves, which is 5th to 9th segments.
In the female earthworm, a genital pore is present in the mid-ventral line of the 14th segment.
While in the male earthworm, a pair of genital pores are present on the ventrolateral sides of the 18th segment.
Besides this, Numerous minute pores called nephridiopores open on the surface of the body.
In each body segment, except the first, last and clitellum, there are rows of S-shaped setae, embedded in the middle of each segment.
Setae can be extended or retracted.
Their principal role is in locomotion.
The body wall of the earthworm is covered externally by a thin non-cellular cuticle below which is the epidermis, two muscle layers, and an innermost coelomic epithelium.
The epidermis is made up of a single layer of columnar epithelial cells that contain secretory gland cells.
The alimentary canal is a straight tube and runs between first to the last segment of the body.
The mouth opens into the buccal cavity from segment 1 to 3, which leads to the muscular pharynx.
A small narrow tube, esophagus present in 5 to 7 segments, continues into a muscular gizzard present in 8 to 9 segments help in grinding soil and decaying leaves.
The stomach extends from the 9th to the 14th segment.
Calciferous glands, present in the stomach, neutralize the humic acids of soil.
The intestine starts from the 15th segment onwards and continues until the last segment.
The characteristic feature of the intestine is the presence of an internal median fold of a dorsal wall called typhlosole.
This increases the effective area of absorption in the intestine.
The alimentary canal opens to the exterior by a small rounded aperture called the anus.
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