Earthworms

Earthworms

Earthworms (pronunciation: /ˈɜːrθwɜːrm/) are a group of invertebrate animals in the phylum Annelida. They are characterized by their long, cylindrical body, lack of limbs, and their ability to burrow through soil.

Etymology

The term "earthworm" comes from the Old English words "eorþe" meaning "earth" and "wyrm" meaning "worm". The name is a direct reference to the creature's habitat and appearance.

Anatomy

Earthworms have a segmented body, each segment or metamere having its own set of organs. The body is covered by a moist, protective cuticle. The anterior end of the worm contains the mouth and the prostomium, a lobe which serves as a covering for the mouth and as a wedge to force open cracks in the soil. The posterior end contains the anus, from which castings are expelled.

Physiology

Earthworms are hermaphrodites, meaning each individual possesses both male and female reproductive organs. They breathe through their skin, as they lack lungs or other specialized respiratory organs. Their circulatory system is closed, consisting of two main blood vessels and numerous smaller vessels that provide nutrients and oxygen to all parts of the body.

Behavior

Earthworms are primarily nocturnal, coming to the surface under the cover of darkness to gather food and to mate. They feed on organic matter in the soil, which they ingest as they burrow. This process of burrowing and feeding improves the quality of the soil, making earthworms vital for soil health and fertility.

Related Terms

• Annelida: The phylum to which earthworms belong.
• Metamere: A segment of an earthworm's body.
• Anus: The opening at the end of an earthworm's digestive tract.
• Hermaphrodite: An organism that has both male and female reproductive organs.

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