Cnidarians (phylum Cnidaria) Include hydra, jellyfish, sea anemones,and corals.

Cnidarians Have two body forms: polyp (sessile) & medusa (free-swimming, motile). Have only one body opening.

Cnidarians: Have stinging cells called nematocysts. Nematocysts are found in tentacles which surround the mouth. Body is made up of two cell layers. Have simple nervous systems.

Two Cell Layers Ectoderm – Outside layer of epidermal cells Gastrodermis/ Endodermis Inside layer of cells Contains digestive cells Mesoglea – Contains the nerve net Jelly like substance

Cnidarian Feeding Habits 1. Prey touches a tentacle… 2. Nematocysts fire, paralyzing prey, toxin is injected... 3. Tentacle contracts, prey is forced into mouth… 4. Prey is digested in gastrovascular cavity.

Cnidarian Feeding Habits Since cnidarians only have one body opening, undigested food must be ejected back out through the animal’s mouth!

Cnidarian Fact: Unlike sponges, cnidarians have a nerve net, which conducts impulses throughout their bodies and brings about contractions of musclelike cells.

Cnidarian Systems Symmetry Radial Support none Digestive nematocysts Gastrovascular cavity Circulatory None

Cnidarian Systems continued Respiratory diffusion through cells Nervous Nerve net Reproductive Asexual - budding Sexual

Examples of Cnidarians Corals produce a hard calcium carbonate skeleton for protection. Form into large colonies Living organisms

More Examples Sea Anemone Large example that is sessile with a large accordian shaped gastrovascular cavity

More Examples Jellyfish There are hundreds of different examples of jellyfish Many are deadly poisonous while others are not at all. They are the medusae stage

The Portuguese Man o’ War Click

Jellyfish Lake, Palau