Updated by: Arabinda Naik
Body Shape: The Obelia polyp is typically elongated and cylindrical in shape, resembling a tiny tube or stalk. It attaches to a substrate, such as rocks or other surfaces, using a specialized structure called a hydrorhiza.
Tentacles: The oral end of the polyp is surrounded by a ring of tentacles, which are equipped with specialized stinging cells called cnidocytes. These tentacles are used for capturing small prey, such as plankton or small organisms, and for defense.
Mouth: At the center of the ring of tentacles is the polyp's mouth. This is the opening through which the polyp can ingest its prey and expel waste.
Gastrovascular Cavity: Inside the polyp's body, there is a gastrovascular cavity, which serves both as a digestive and circulatory system. Nutrients obtained from prey are digested in this cavity, and the resulting nutrients are distributed throughout the polyp's body.
Epidermis: The outermost layer of the polyp is covered by an epidermis, which provides protection and helps maintain the polyp's structural integrity.
Reproductive Structures: In Obelia, polyps can have reproductive structures, such as gonophores, which are responsible for producing medusae (the free-swimming, jellyfish-like stage) through a process known as asexual reproduction. Medusae are released from the polyps and eventually develop into mature individuals, continuing the life cycle.
Hydrorhiza: The base of the polyp, known as the hydrorhiza, is an attachment structure that anchors the polyp to the substrate. It also gives rise to new polyps and can spread to form colonies of interconnected individuals.