Have stinging cells (a must to be a cnidarian) to capture prey Have radial symmetry –Central point Soft Corals, Hard Corals, Sea Fans, Hydra, Jellyfish, Sea Anemones

Create coral reefs at growths of ½ inch per year Deposit skeleton of calcium carbonate (limestone) Photosynthetic and symbiotic dinoflagellates (zooxanthellae) live within coral structure and provide energy to growing coral.

Toxins in nematocysts are quite potent Of the 9,000 to 10,000 cnidarians, only a handful pose a threat to humans In most cases, nematocysts are not strong enough to penetrate skin

Organ Pipe Coral

Sea Surface Temperature Changes

Stomach Mouth

Distinct floats that allow wind to push them through the water Sting can be life threatening Tentacles exceed 40 meters (131 ft) in length

Lives in tentacles of Man-of-War jellyfish much like a clownfish lives in an anemone Immune to sting Use jellyfish for protection in open ocean

Most dangerous to humans Potent toxin can kill an adult human within minutes –Cause paralysis and lyse blood cells Fortunately, rare in most parts of world