Earthworm Morphology And Anatomy

Earthworm

An earthworm is a reddish-brown terrestrial invertebrate that inhabits the upper layer of the moist soil.
The common Indian earthworms are Pheretima and Lumbricus.

Morphology of earthworm

The earthworm has a long cylindrical body. The body is divided into more than a hundred (100-120) short segments called metameres.
The first body segment is called the peristomium (buccal segment), which contains the mouth. In mature worms, segment 14-16 are covered by a prominent dark band of glandular tissue called the clitellum. Thus, the body is divisible into three prominent regions: preclitellar, clitellar, and postclitellar segment.

Figure: body of an earthworm

Anatomy of earthworm

1 Alimentary canal of the earthworm

The alimentary canal is straight and runs between first to the last segment of the body. The alimentary canal comprises of mouth or buccal cavity (1-3 segment), pharynx, esophagus (5-7 segments), muscular gizzard (8-9 segment), stomach (9-14 segment), intestine (15 to the last segment).

Figure: Alimentary canal of the earthworm

2 Circulatory system of earthworm

Closed type of blood vascular system, as blood is confined to heart and blood vessels.

Figure: closed Circulatory system

2.6.2.3 Nervous system of earthworm

The nervous system is well developed and consists of central, peripheral, and autonomic nervous systems.

2.6.2.4 Excretory system of earthworm

Figure: Nephridial system of earthworm

3 Reproductive system of earthworm

An earthworm is monoecious but cannot fertilize their egg as they are protandrous.
Male reproductive system includes testes, testes sacs, seminal vesicles, vasa differentia, prostate glands and accessory glands.
The female reproductive system consists of ovaries, oviducts, and spermatheca.

Figure: Reproductive system of earthworm