1. Phylum Cnidaria or Coelenterata
Jellyfish, anemones, corals

3. The Basics
Two tissue layers - an outer epidermis and an inner gastroderm
Nerve net with stinging capsules called nematocysts
Radial symmetry with 2 body types - a polyp and/or medusa

7. The coral animal may live as a free-floating polyp or build colonies into reefs. Not all corals build reefs.

8. Stony Coral Hermatypic or reef builders
Polyp grows in 6 parts to form a body of calcium carbonate
Brain coral and staghorn coral

10. Soft Coral Polyps with 8 tentacles
While part of the reef, they do not build reefs because their bodies are a soft keratin.
Sea fans and gorgonians

11. Hydrocoral False corals resemble the anemone
contain powerful nematocysts that cause skin irritation
Fire coral

12. Some cnidarians exist as individuals and others live as colonies like the Portuguese man-of-war.

13. It has a gas filled float and individuals that function like specialized organs. Some are carnivores with digestion in food vacuoles.

14. Cnidarians
Class varieties

15. Hydrozoans - Class Hydrozoa
Feathery or Bushy colonies of tiny polyps
Polyps may be specialized
Attach to pilings, shells, seaweed, etc.
Siphonophores - hydrozoans that form drifting colonies (Portugues man of war)

16. Scyphozoans - Class Scyphozoa
Larger jellyfish
Bell of some medusae may reach 2 m.
Some are the most dangerous in the world

17. Anthozoans - Class Anthozoa
Solitary or colonial polyps that lack a medusa stage.
Sea anemones
Stony corals and sea fans

18. The case of the killer Cnidarians
Textbook readings
The case of the killer Cnidarians