Oral arm

Oral Arm

Chrysaora quinquecirrha, commonly known as the Atlantic sea nettle, displaying its oral arms.

The oral arm is a structure found in certain species of Cnidaria, particularly within the class Scyphozoa, which includes the true jellyfish. These arms are extensions of the manubrium, the central structure that hangs down from the center of the bell of the jellyfish. The primary function of the oral arms is to aid in the capture and ingestion of prey.

Structure and Function

Oral arms are typically long, flexible, and often frilled or lobed. They are equipped with numerous cnidocytes, which are specialized cells that contain nematocysts, or stinging organelles. These nematocysts are used to immobilize prey, which is then transported to the mouth located at the center of the manubrium.

The oral arms also play a role in the digestion process. Once prey is captured and immobilized, it is moved along the oral arms to the mouth, where it is ingested into the gastrovascular cavity for digestion. The structure of the oral arms can vary significantly between different species of jellyfish, reflecting adaptations to their specific feeding strategies and environments.

Species Examples

One well-known species that possesses prominent oral arms is the Chrysaora quinquecirrha, commonly known as the Atlantic sea nettle. This species is characterized by its long, trailing oral arms that can extend several times the length of its bell. The oral arms of Chrysaora quinquecirrha are used to capture a variety of prey, including small fish and zooplankton.

Related Pages

• Cnidaria
• Jellyfish
• Cnidocyte
• Nematocyst
• Gastrovascular cavity