[2] Cnidaria

• Over 10 thousand species
• Stinging cells

  Cnidocytes
• Organelle that causes stinging

  Nematocyst
• Cnidarians exhibit radial symmetry
• Polyp is a benthic form of cnidarian with an opening surrounded by tentacles
• The medusa is the free-floating form of a cnidarian
• Most venomous animal in the world

  Carukia barnesi, common name Irukandji jellyfish
• Portuguese man-of-war scientific name

  Physalia physalis
• 3 Cnidarian Groups

  1. Hydrozoans (Colonial organisms)
  2. Scyphozoans (True jellyfish)
  3. Cubozoa (Box jellyfish)
  4. Anthozoans (Corals, anemones)
• Hydrozoan polyps:

  1. Zooid - general term for polyp
  2. Gastrozooid - feeding polyp
  3. Gonozooid or Gonangium - reproductive polyp
• Largest known jellyfish

  Lions Mane Jellyfish, scientific name Cyanea capillata
• Also called the immortal jellyfish

  Turritopsis dohrnii
• Turritotopsis dohrnii undergoes dedifferentiation to go back to less specialized cells or tissues