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Cnidarians

Cnidarians Jellyfish, corals, hydra and anemone Defining Characteristics Radial Symmetry Tentacles with nematocysts (stinging cells) No cephalization (no head) Two stages: polyp and medusa Endoderm and ectoderm Radial Symmetry

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Cnidarians

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  1. Cnidarians Jellyfish, corals, hydra and anemone

  2. Defining Characteristics • Radial Symmetry • Tentacles with nematocysts (stinging cells) • No cephalization (no head) • Two stages: polyp and medusa • Endoderm and ectoderm

  3. Radial Symmetry Like a radial tire, can be dissected along any plane into equal mirror images.

  4. Nematocysts – stinging cells • Stinging barb at the end of tentacles • The barb is discharged like a toy popgun. Some contain toxins.

  5. Nervous System • No cephalization (no head) • No central Brain • Impulses cause muscle contractions and responses

  6. Stages in Cnidarian Life Cycle • Polyp: sessile and tube-shaped with the opening (mouth) facing up and surrounded by tentacles • Medusa: free-swimming form with mouth and tentacles facing down

  7. Polyp

  8. Medusa

  9. Sexual: only in medusa stage Asexual: in either stage thru budding A budding hydra Reproduction in Cnidarians

  10. Body Design • Tentacles capture food and carry to the mouth. • Waste is expelled through the mouth.

  11. Types of Cnidarians • Hydrozoans: the hydras • Scyphozoans: the jellyfish • Anthozoans: corals and sea anemone

  12. Hydrozoans • Include the hydra and the man-of-war • Mostly sessile

  13. Named for the famous greek monster, Hydra Hydra

  14. Hydra Anatomy (know this!)

  15. Man-of-war Made of a colony of polyps, each specialized for a single task. One polyp forms the gas-filled float, while others are responsible for feeding or reproduction.

  16. Scyphozoans: The Jellyfish • Can be luminescent (create their own light) • The medusa stage is dominant • The sting is venomous

  17. Polyp form only Two types: Corals Anemone Anthozoans: Corals and anemone

  18. Corals • Warm Water only • Forms colonies • Reefs formed from new coral build on old layers. • Reefs provide ecosystem for marine animals. • Reefs grow at 2mm/year.

  19. Notice the eight stinging tentacles on the coral in this colony

  20. Coral have a symbiotic relationship with zooxanthellae, a photosynthetic protista. The bright coral colors come from zooxanthallae The greenish color of this color is due to the zooxanthellae which live inside of it. Zooxanthellae and Coral

  21. Sea anemone • Unlike coral, each anemone lives as an individual • Anemone can live for centuries

  22. Stinging tentacles of an anemone

  23. Commensalism: anemone and Clownfish Clownfish are immune to the anemone toxins, and can live safely within the tentacles, protected from predators. The anemone isn’t helped or hurt by the clownfish.

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