Stomochord

Stomochord is a structure found in the phylum Hemichordata, specifically within the class Enteropneusta, commonly known as acorn worms. The stomochord is a diverticulum of the buccal cavity, extending into the proboscis. It is often mistaken for a notochord, a structure found in chordates, but it is not homologous to it.

Etymology

The term "stomochord" is derived from the Greek words "stoma", meaning mouth, and "chord", meaning string or cord. This refers to the structure's location and appearance, extending from the mouth area of the organism.

Structure and Function

The stomochord is a tubular structure that extends into the proboscis of acorn worms. It is a diverticulum of the buccal cavity, meaning it is an outpouching or protrusion. The stomochord is filled with fluid and is thought to assist in maintaining the rigidity of the proboscis, which is important for the burrowing lifestyle of many acorn worms.

Despite its name and location, the stomochord is not homologous to the notochord found in chordates. The notochord is a flexible rod that provides support in the embryonic stages of all chordates, while the stomochord is a structure unique to hemichordates and does not provide the same function.

Related Terms

• Hemichordata: The phylum to which organisms with a stomochord belong.
• Enteropneusta: The class of hemichordates that includes acorn worms, which possess a stomochord.
• Notochord: A structure found in chordates, often confused with the stomochord due to its similar name and location.
• Proboscis: The part of the acorn worm's body into which the stomochord extends.

See Also

• Chordate
• Acorn worm
• Buccal cavity

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