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CROSSWHITE 1
I. Phylum Cnidaria- hydra, jellyfish, and corals.
A. fresh water & mostly marine
B. benthic colonial & planktonic
C. diagnostic features
1. radiate, eumetazoans
2. tissue grade
3. diploblastic
4. predaceous
a. cnidocyte- stinging cells with nematocysts
1. cnidocils in hydrozoa & scyphozoa
2. protein toxin
b. tentacles
c. sensory organs: statocysts & ocelli
5. gastro-vascular cavity- plays an important roll as a hydrostatic skeleton
6. polymorphic (polyp & madusae forms)
7. oral/aboral surfaces
8. manubrium- bears the mouth
9. vellum- shelf of tissue extending from the margin of the bell to the manubrium;
provides jet propulsion
II. General Structure & Function:
A. polymorphic: fig. 4-5
1. medusoid
2. polypoid
3. alternation of generations
B. histology:
1. epidermis- contain myoepithelial cells
2. gastrodermis- lines the gastrovascular cavity nutritive cells; flagellated;
phagocytic
3. mesoglea- secreted layer between epidermis and the gastrodermis; gelatinous
consistency
C. nutrition/feeding: carnivores w/ extracellular digestion & phagocytosis; zoolchlorellae
or zooxanthellae
D. nervous system: "nerve net" w/ receptor cells
E. respiration/excretion: diffusion/ammonia
F. reproduction: budding; sexual reproduction in medusae; planula larvae
1. Hyda- sexual reproduction occurs in fall to produce winter eggs.
2. many are dioecious
CROSSWHITE 2
III. Classification:
A. Class Hydrozoa (hydroids); 2700 spp.
1. mostly colonial polyps; Obelia, fig. 4-15
2. Physalia- Portuguese Man-O-War; colonial pelagic hydrozoan; pneumatophores,
fig. 4-25
3. Hydra- solitary polyps
4. Craspedacusta; found in Oklahoma; contains a symbiotic algae Chlorella
B. Class Scyphozoa (true jellyfish); 200 spp.
1. mostly marine
2. medusae dominance
3. Some dangerous species
4. Cassiopea- swims upside down in shallow intertidal pools
5. Aurelia; fig. 4-35
medusa--->gametes--->zygote--->planula--->scyphistoma--->strobilus--->ephyra
C. Class Anthozoa (anemones, corals, & sea fans); 6000+ spp.
1. all marine
2. solitary or colonial forms; polyp form only
3. gastrodermis bears nematocysts w/o opercula
4. some hermaphrodites
5. stony corals produce CaCO3 skeletons; sclerosepta
6. often contain zooxanthellae
7. octocorals: sea pansies, sea fans, whip corals, & pipe corals
a. eight pinnate tentacles
b. Gorgonians figs. 4-52 & 53
c. O. Stolonifera- organpipe coral- polyps encased in parallel calcareous
tubes
8. coral reefs support diverse associations of marine organisms
9. structurally heterogeneous habitat
IV. Ctenophora- comb jellies ~50 spp.
A. poorly known group
B. delicate
C. Comb rows; figs. 4-66 & 67