1. Phylum Cnidaria
Cnidarians Include Hydras, jellyfish, sea anemones & corals
Radially symmetrical
Two basic forms:
Polyp: Cylindrical form which attach bases to substratum
Medusa: Flattened, mouth down version of the polyp. Moves freely

2. Forms of Cnidarians

3. Body Plan Basic Body Plan: Has an outer epidermis
Has an inner gastrodermis which forms a gastrovascular cavity
Has a middle "jelly filled" layer called mesoglea

4. Cnidocytes
Cnidarians are predators which have tentacles possessing batteries of special cells called Cnidocytes
Cnidocytes contain special stining capsules called nematocysts.
When triggered, these cells shoot out a discharge thread which can entangle and/or poison it's intended prey

6. Reproduction 4 Major classes
Reproduction can occur sexually by fertilization of egg and sperm forming larvae, which for jellyfish is called a planula (during medusa stage)
Reproduction can also occur asexually through budding (during polyp stage)
4 Major classes
Class Hydrozoa: Hydras
Class Scyphozoa: Jellyfish
Class Anthozoa: Anemones and corals
Class Cubozoa: box jellyfish

7. Class Hydrozoa: The Hydras
Mostly polyp form during their life
Generally microscopic, found in intertidal zones
Do not display senescence (they do not age/deteriorate)
Example: Portuguese Man-o-war, Fire coral!

8. Class Scyphozoa: The Jellies
Generally referred to as jellyfish
Medusa stage is dominant
Can alternate between sexual/asexual reproduction
Aggressive predators, and can be dangerous to humans
Jelly

9. Class Anthozoa: Anemones, Sea fans & Corals
Appear like plants but are animals.
Polyp form dominant.
Corals build calcium shells to protect themselves
Have symbiotic relationship with algae called….
Can build extensive masses which act as a unit more than individuals. (coral bleaching)
Found since the late pre-Cambrian period (550million years ago)
Can use their nematocyst to catch prey but mostly prefer plankton and symbiotic relationships with dinoflagellates.
Anemone
Coral Polyps

10. Coral Reefs
Clownfish living in
An anemone

11. Cubozoans
Similar to scyphozoan except they have 4 tentacles, swim a bit faster, and have “seeing” ability.
Get their name from their box-like appearance.
Most deadly jellyfish, can be lethal.

12. Cassiopea Upside down jellyfish (scyphozoan)
Very common in FL, often in mangrove ecosystems
Mostly rely on zooxanthellae
Easily confused for anemones
Some crabs carry them on their back for defense.