Characteristics :

  • Body symmetry is radial, similar to a pie that has a definite top and bottom but no definite right or left sides
  • May go through two body forms in completing the life cycle: the hollow, cylindrical, often stationary form is called a polyp; the free-swimming, hollow, bowl-like form is called a medusa
  • Have many cells, some specialized and some organized into tissues
  • Body consists of two cell layers surrounding a hollow cavity with an opeing that functions both as a mouth and for ejecting wastes
  • Have arm-like parts called tentacles that sorround the mouth
  • Have stinging cells on tentacles for food-getting and defense
  • Are carnivores; eat by capturing prey with tentacles
  • Kingdom: Animalia
    • ​Phylum: Cindaria
      • Class: Anthozoa (coral, anemones, others), Cubozoa (box jellies), Hydrozoa (hydras, fire corals, others), Scyphozoa (jellyfish)
Student Challenge:
  • Cnidarians typically go through two developmental stages, each with a body form that looks different from the other. These two body forms are calle polyp and medusa. How does each shape help it survive in its ecological niche?