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