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Phylum Cnidaria Hydras, Jelly-fish, Sea Anemones & Coral Gastrovascular Cavity Cnidarians get their name from…. Polyp Medusa Cnidarians are soft-bodied, carnivorous animals, that have stinging tentacles arranged in circles around their mouths. They are the simplest of animals to have body symmetry & specialized tissue. They have radial symmetry in both the polyp and medusa stages. A digestive chamber with a single opening in which cnidarians, flatworms, & echinoderms digest food (an internal space). “Cnidocytes”-stinging cells that are located along their tentacles. They help a cnidarian survive by paralyzing their prey. POLYP- usually the SESSILE stage in the life cycle of a cnidarian that has a cylindrical body with arm-like tentacles. The mouth points upward. In jelly-fish the polyp reproduces asexually. MEDUSA- MOTILE stage of the life cycle of a cnidarian that has a bell-shaped body with a mouth on the bottom. In the jelly-fish the medusa reproduces sexually & most sexual reproduction is by EXTERNAL reproduction. 3 Classes of Cnidarians Schyphozoa “Cup Animals” Anthozoa Jelly-fish which live most of their lives as medusas Sea anemones & corals have only the polyp stage in their life cycle. “Flower Animals” Hydrozoa Fresh water hydra lacks the medusa stage & lives as solitary polyps. Other hydra live as POLYP COLONIES with each colony specialized to perform a different function. EX: Portuguese Man Of War