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Phylum Cnidaria

Phylum Cnidaria. Jelly Fishes. Sea Anemones. Corals. Phylum Cnidaria. A.k.a Coelenterata or Radiata. Differ from sponges - have rudimentary organs. Morphology. Body wall - 3 layers Epidermis Gastrodermis Mesoglea. Body plans. Sessile - Polyp (hydranth or hydroid)

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Phylum Cnidaria

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  1. Phylum Cnidaria

  2. Jelly Fishes

  3. Sea Anemones

  4. Corals

  5. Phylum Cnidaria • A.k.a Coelenterata or Radiata

  6. Differ from sponges - have rudimentary organs

  7. Morphology • Body wall - 3 layers • Epidermis • Gastrodermis • Mesoglea

  8. Body plans • Sessile - Polyp (hydranth or hydroid) • Cylindrical stalk and oral end with tentacles

  9. Body Plan • Free swimming - Medusa • Bell shaped • Mesoglea constitutes bulk

  10. Cell Types • Epithelio-muscle cells • Cover and protect • Can contract (muscular properties) • Interstitial cells • Production of gamets • Mucous secreting cells (Gland cells) • Nerve cells • Cnidocytes

  11. Cnidocyte • On Tentacles • Defense and feeding • Nematocyst • Cnidocil - trigger

  12. Nervous System • First time • Nerve net • 2 nets • Associated with epidermis and gastrodermis

  13. Classification • 3 Classes • Hydrozoa • Scyphozoa • Anthozoa

  14. Hydrozoa • Polymorphic • Polyp - Hydra • Medusa - Obelia • Simple gastrovascular cavity - no septa • No nematocysts in digestive cavity • Solitary or colonial

  15. Close-up of Hydroid

  16. Hydroid medusa

  17. Composition of Colonies • 3 types of individuals • Gastrozooid - responsible for feeding also numerous • Gonozooid - sexual reproduction • Dactylozooids - defense and food capture

  18. Life Cycles • 3 basic types • Obelia - both polyp and medusa stage • Hydra - only polyp • Asexual reproduction - budding • Physalia - Colony attached to float called Pneumatophore

  19. Scyphozoa • Exclusively marine • Medusa dominant stage • Much larger in size compared to hydrozoan medusae

  20. Scyphozoa • Mesoglea makes up large portion of body • Gastrovascular cavity divided by septa • complex system of canals in medusa to help move food and oxygen • Muscular system on outer edge of medusa • Very toxic - can kill in 30 secs or less

  21. Sense organs • 8 compound marginal sense organs • 2 sensory pits - chemoreception • 1 ocellus (eye spot) - light sensing • tactile structures - touch sensitive • 1 statocyst - orientation and balance

  22. Reproduction

  23. Anthozoa • None have medusa - Only Polyp • Hence Sessile • Several Septa in Gastro-vascular cavity • Attached to substrate by Pedal Disk

  24. Phylum - Ctenophora Combjellies or Sea Walnuts

  25. Offshoot of Medusa like Cnidarian • Transparent animals • Never colonial • Free swimming • No nematocysts instead have COLLOBLASTS – adhesive cells

  26. Characteristics • 8 rows of fused cilia (combs) • Nervous system – nerve net • Single sense organ – Statocyst • Cydippid larva • Bioluminescence

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