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 Hyrdrozoans1. Hydra – small freshwater organisms

-polyp form only-25-30 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

1st – penetrants

penetrate and inject poison

2nd – volvents

recoil and entangle prey

3rd – 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 AnthozoanA. Facts

1. meaning “flower animal”2. No medusa stage3. Only marine4. octomerous – 8 tentacles5. hexamerous – 6 tentacles

B. Notable Anthozoans1. 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