Phylum Cnidaria Kingdom Animalia Phylum Cnidaria Classes:HydrozoaScyphozoaAnthozoaCubozoa Roxanna Shadmehr Holly Hoang Olivia Miller

Major Characteristics  Sea anemones  Jellyfish  Corals  About 10,000 species  The next level up of organization after sponges –Makes it possible for them to swim and engulf prey

Characteristics  Radial symmetry –Similar parts of the body are arranged around a central axis  Capture prey by stinging them with specialized cells in their tentacles  Two forms –Polyp –medusa

Stages  Polyp –Sac-like stage –Mouth and tentacles pointing upward  Medusa (jellyfish) –Upside-down polyp –Adapted for swimming  Some have both a polyp and medusa stage, others have only one or the other

Feeding  Carnivores  Capture prey with nematocysts –Stinging structures found in tentacle cells  Consists of a capsule –Ejects thread that is sticky, armed with spikes, or contains toxins  Prey passes into gut and is digested

Behavior  No brain or true nerves, but have nerve cells  Creates nerve net that send impulses all over  Causes complex behavior –Ex. Some anemones can tell if others are part of the same clone

Reproduction  Medusae release gametes  Fertilized eggs turn into larvae that settle at sea floor  Develops into a polyp  Multiplies into a colony of polyps  Releases medusae buds  Several variations of this basic life cycle

Hydrozoans (class)  Feathery/bushy colonies of tiny polyps  Attach to shells, seaweeds, and pilings  Specialized for –Feeding –Defense –reproduction

Siphonophores  Hydrozoans formed into drifting polyp colonies  Polyps specialized as floats –Gas-filled –Droplets of oil  Long tentacles to capture prey  Can be harmful to humans

Scyphozoans (class)  Larger jellyfish  Common in all oceans  Medusa is dominant stage in life cycle  Polyps are small, and some lack a polyp stage  Rounded body (bell) can have 3 m diameter  Swim with rhythmic contractions of bell  Extremely painful/sometimes fatal stings

Anthozoans (class)  Solitary or colonial polyps that lack a medusa stage –Sea anemones –Corals –Gorgonians (sea fans)  More complex –Gut has several partitions (septa) which aid in digestion of larger prey and provides support

Sea Anemones  Common  Colorful  Often have large polyps

Corals  Have calcium carbonate skeletons  Occur in cold waters  In tropical waters, they form coral reefs.  Includes groups of mostly colonial anthozoans

Gorgonians  Sea fans  Colonial  Secrete a tough, branching skeleton made of protein

Precious & Black Corals  Precious –Gorgonians with fused red or pink calcareous spicules in addition to the protein skeleton  Black Corals –Not a gorgonian –Secrete a hard, black, protein skeleton

Precious Corals: Black Corals: