Kingdom: Animalia, Phylum: Cnidaria Tentacle Phraynx Gonads Column Septum Cinclide (pore) Acontium (defensive stinging tentacle) Pedal disk Oral disk Mouth Collar Stomata Septum Retractor muscle Cnidaria is a phylum containing over 9000 species found only in aquatic and mostly marine environments. “Cnidaria” comes from the Greek word "cnidos," which means nettle. There are two major body forms among the Cnidaria - the polyp (sea anemones and corals) and the medusa (jellyfish). There are four major groups of cnidarians: • Anthozoa: corals, anemones, and sea pens • Cubozoa: box jellies • Hydrozoa: siphonophores, hydroids, fire corals • Scyphozoa: jellyfish Sea anemone polyp anatomy Cnidaria have stinging cells called nematocysts that are used for defence or capturing prey. When the trigger is touched the nematocyst tube springs out and injects venom into the prey. Red, or southern, or bubble, or mulberry anemone Phlyctenanthus australis Waratah anemone Actinia tenebrosa (pronounced “Nye-dare-ree-ah”) Sea anemones sometimes found in the touch tank Image by Byron Inouye manoa.hawaii.edu