Radiate Animals Cnidarians and Ctenophores Radiates Are Eumetazoans

Radiate Animals Cnidarians and Ctenophores

Radiates Are Eumetazoans

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