1. Jellyfish, Corals, and Sea Anemones
Phylum Cnidaria
Jellyfish, Corals, and Sea Anemones

2. General Characteristics
Tentacles
Hydrostatic skeleton
Nerve net
Radial symmetry
Saclike digestive system (only one opening for mouth/anus)
Two layers of cells with mesoglea (jelly-like material) in between.
Lack special organs for respiration, excretion, and have no blood

3. Nematocysts (stinging cells) – used for feeding, defense, and some contain toxins.

4. Two Body Forms of Cnidarians
Medusa – free floating, motile, part of the plankton, tentacles and mouth point down
Polyp – sessile, part of the benthic community, tentacles and mouth point up.

5. Classes of Cnidarians Hydrozoans Most are colonial
Polyp body form for most of its life cycle
Some do not have a medusa stage others do not have a polyp stage, but most have both stages in their life cycle
Examples: Portuguese Man-o-War, Hydra

6. Scyphozoans Most are solitary
Medusa body form for most of its life cycle
Examples: true jellyfish like the Moon Jelly (Aurelia)

7. Cubozoa Box Jellyfish (Sea Wasp)
The deadliest jellyfish in the world are a type of box jellyfish, with the typical cube body shape
Not all species are deadly, but can cause very painful stings

8. Anthozoans Only found in the polyp body form
Reproduce both asexually (budding) and sexually (shed eggs and sperm into the water)
Three groups of anthozoans:
Anemones – soft fleshy polyps, usually solitary
Soft Corals – sea fan and sea whips
Hard Corals – which have a calcareous skeleton (usually) and build coral reefs, usually colonial
                           

9. Most anthozoans have a symbiotic relationship with a dinoflagellate known as zooxanthellae living in their tentacles that produce food for the coral in exchange for a place to live and nutrients.