Zoology Phylum Cnidaria

I. Intro to Cnidarians Cnidocytes/nematocysts  “stinging organelles” Ancient group dating back 700 million years Mostly marine / non-terrestrial Sessile  lack movement Free floaters Effective predators Ex: Jellyfish, anemones, stony corals

II. Class Hydrozoa A. Facts 1. Both Medusa and Polyp stages 2. Reproduce sexually and asexually

B. Notable Hyrdrozoans 1. Hydra – small freshwater organisms -polyp form only mm in length -shares a mouth and anus -sessile … attach to plants,rocks, etc.  tentacles sway in the current -tentacles (6-10) contain nematocysts = stinging cells release neurotoxins  paralyze prey

a. 3 types of nematocysts 1 st – penetrants  penetrate and inject poison 2 nd – volvents  recoil and entangle prey 3 rd – glutinants  secrete adhesives (used in movement and locomotion)

b. Favorite Prey of Hydra -Daphnia -worms -small insects -small crustaceans 2. Portuguese Man of War a. Pneumatophore – sac like structure filled with gas -allows movement (wind + water currents)

III. Class Anthozoan A. Facts 1. meaning  “flower animal” 2. No medusa stage 3. Only marine 4. octomerous – 8 tentacles 5. hexamerous – 6 tentacles B. Notable Anthozoans 1. Sea Anemone -very colorful -prefer warmer waters

a. Mutualistic Relationships -hermit crabs – attach to backs  provides protection  gets small morsels of food -clownfish – skin mucous prevents nematocysts from stinging  provides protection  lures unsuspecting fish in

IV. Class Scyphozoa A. Facts 1. Common Jellyfish a. “Scypho” = cup animals or bell shaped 2. Found in all oceans 3. Notable Scyphozoans a. Cassiopeia -floats upside down B. Note – box jellyfish is not found in this class  class cubozoa