3/26/12 If both sponges and cnidarians have two layers of cells, why are they in different phyla? Key terms: cnidocytes, nematocysts

Phylum Cnidaria

Common name : Stinging cell animals Multicellular with true tissues – some simple organs. Radial Symmetry 2 body designs: – Polyp (vase shaped, sessile) - Medusa (bell, free)

2 cell layers – Epidermis (ectoderm) – Gastrodermis (endoderm) – Separated by mesoglea (where jellyfish get their name) – Digestive system with one opening

Special Cell type: – Cnidocyte (stinging cell) Used for defense and feeding Nematocyst is released when cnidocytes are pressured. (some can be triggered by the presence of certain chemicals) They inject toxin into the prey. Concentrated in epidermis on tentacles.

Classification: – Approximately 9,000 species – 4 classes: Hydrozoa – 2,700 species. Both freshwater and marine Colonial polyps (some solitary) Ex: Hydras, Physalia nvertebrates-animals/other- invertebrates/manowar_portuguese/ nvertebrates-animals/other- invertebrates/manowar_portuguese

Classes’ cont’d – Scyphozoa -200 species All marine Solitary Free swimming or floating medusae (planktonic) assignment-discovery-jellyfish-reproduction-video.htm assignment-discovery-jellyfish-reproduction-video.htm assignment-discovery-anatomy-of-a-jellyfish-video.htm assignment-discovery-anatomy-of-a-jellyfish-video.htm

Class Cubozoa – Box jellies – Very toxic Average life span in the wild: Less than 1 year Size: Tentacles 10 ft (3 m) long; body 10 in (25 cm) across Weight: Up to 4.4 lbs (2 kg) Did you know? Sea turtles are unaffected by the sting of the box jellyfish and regularly eat them

Symptoms Discuss… – How are box jellies different from other jellyfish? – Why is it important to study the evolutionary relationships of box jellies?

Classes cont’d Anthazoa – 6,000 species – Corals and anemones – Polyp dominates (sessile) – Only marine – Giant Green Anemone Feeding Video | Monterey Bay Aquarium Giant Green Anemone Feeding Video | Monterey Bay Aquarium