Radiate Animals
Cnidarians and Ctenophores
Radiates Are Eumetazoans
PhylumC nidaria
H ydra , je lly fish e tc ...
Phy lumC tenophoraC om b je llies
G rade R ad ia taR a dia l Sym etry
D iv is ion Pro tos tom ia D iv is ion D eu te ros tom ia
G rade B ila tera taB ila tera l Sym etry
Eum etazoaTrue T issue s
Radiates
• Radial symmetry• Tissue level organization• Two germ layers
– Ectoderm and endoderm• Nerve net (simple nervous system)• Extracellular digestion
Radiate Phyla
• Cnidaria • Ctenophore
Phylum Cnidaria
• Two forms– Polyp– Medusa
• Tentacles• Nematocyst
Polyp and Medusa Forms
Class Hydrozoa
• Mostly colonial• Polyp and medusa life cycle for most• Hydra – non colonial polyp stage only• Obelia – typical colony
– Chiton exoskeleton– Extracellular and intercellular digestion
Hydra
Hydra Tissue Structure
Obelia Life Cycle
Gonionemus
Class Scyphozoa
• Larger jellyfish• Not colonial• No vellum• Internal gastric pouches
– Radial canals lead to ring canal
Aurelia Life Cycle
Medusa
Strobilia
Class Anthozoa
• Subclasses– Zoantharia – anemones, hard coral– Alcyonaria – sea fans (soft coral)– Ceriantipatheria – tube anemone, horny coral
• Polyp form, no medusa stage• Partitioned gastrovascular cavity
Sea Anemone
Sea Anemone
Anemone Fish (Clown Fish)
Zoantharian Coral
• Calcium carbonate exoskeleton secreted externally from base
• Contain mutualistic zooxanthallae algae
• Live in colonies• Hexamerous symmetry
Coral Polyps
Alcyonarian Coral
• Octomerous symmetry
• Colonial• Can communicate
with members of colony through tubes call solenia
• Endoskeleton composed of spicules and protein and secreted within mesoglea
Soft Corals
Phylum Ctenophora
• Comb Jellies• Move using cilia
– Comb plates• Do not have nematocysts
– Colloblasts capture food
Comb Jelly Tentacle
Comb Jelly Structure
Comb Jelly Cilia
Predatory Comb Jellies Approaching Prey
Predatory Comb Jelly Engulfing a Comb Jelly
Comb Jelly After a Meal