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Phylum Cnidaria

Phylum Cnidaria. Jelly fish, hydra, coral, and sea anemones. General Characteristics. Cnidaria - name derived from stinging cell cnidocyte More highly organized than sponges but still very simple. Radial symmetry No advancement above tissue level organization

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Phylum Cnidaria

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  1. Phylum Cnidaria Jelly fish, hydra, coral, and sea anemones

  2. General Characteristics • Cnidaria- name derived from stinging cell cnidocyte • More highly organized than sponges but still very simple. • Radial symmetry • No advancement above tissue level organization • Aquatic-mostly marine (few in fresh water) • Shallow warm marine habitats • No terrestrial species • Mostly sessile some mobile • Predatory

  3. Cnidocytes • Specialized stinging cells • 20 different types • Important in taxonomic determinations • Formed only by Cnidarians • Located mainly on tentacles

  4. Cnidocyte anatomy • Capsule composed of chitin like material containing a coiled thread with barbs • Some contain toxin • Others recoil • Capsule covered by operculum (lid) • Cnidocil- modified cilium (trigger) • Discharged by a combination of tensional forces generated during the formation of the cnidocyte (osmotic pressure)

  5. Cnidocyte function • Small organic molecules from prey “tune” the mechanoreceptors, sensitizing them to the frequency of vibration caused by prey swimming • Tactile stimulation of the cnidocil causes the cnidocyte to discharge • Jellyfish feeding on fish http://www.youtube.com/watch?v=bcmLxsJ5SAg

  6. Morphologically Dimorphic • Polyp • Medusa

  7. Polyp • Hydroid form • Sedentary sessile life • Tubular body with a mouth directed upward at one end surrounded by tentacles • Attached to the substrate by a pedal disc or other device • May live single or in colonies • Usually reproduce sexually • Anthozoa

  8. Medusa • Free swimming • Bell or umbrella-shaped bodies • Mouth is centered on the concave side • Tentacles extend from the rim of the umbrella

  9. Body Plan • Outer epidermis • Inner gastrodermis which forms a gastrovascular cavity • Has a middle “jelly filled” layer called a mesoglea

  10. Nervous system • Nerve net • Two interconnected nerve nets • Diffuse nervous system • No cephalization • Neuromuscular system • Receives external stimuli • Stimulates the epitheliomuscular cells and nematocysts

  11. 4 Classes of Cnidarians • Hydrozoa • 2,700 species • Hydroids, fire corals, and Portuguese man-of-war • Scyphozoa • 200 species • True jellyfishes • Anthozoa • 6,000 species • Sea anemones, stony corals and soft corals • Cubozoa • 15 species • Cube jellyfishes

  12. Class Hydrozoa • Freshwater or marine • Solitary or colonial • Life cycle with both polyp and medusa, one or the other form may be suppressed • Asexual polyp form • Sexual medusa stage • Simple gut cavities • Ectodermal gonads • Statocysts and ocelli (special light sensing organs) may be present in some medusa

  13. Class Hydrozoa: Hydra • Freshwater solitary polyp • Habitat • Found worldwide under leaves or lily pads in cool streams or pools. • 25-30 mm • Hydrostatic skeleton

  14. Class Hydrozoa: Hydroid colonies (Obelia) • Have both polyp and medusa stage in their life cycle

  15. Obeliaanatomy • Polyp • Hydrorhiza- rootlike stalk • Hydrocauli- stalks • Coenosarc- living part of the stalk • Perisarc- protective covering (chitin) • Thecate- have perisarc (cups) • Athecate- thin pericarc (naked) • Hydranths- feeding polyps • Gonangium- reproductive polyp • Medusa • Manubrium- hold mouth • Velum- margin of the bell partly closes and is used for swimming

  16. Class Hydrozoa: Other Hydrozoans • Physaliaphysalis Portuguese man-of-war • Pneumatophore -float

  17. Class Scyphozoa: The jellies • Large jellyfish • may exceed 2 m and have tentacles 60 to 70 meters long • Most are 2 to 40 cm in diameter • Found in the open sea

  18. Aurelia

  19. Scyphozoa anatomy • No velum • Manubrium divided into four oral arms • Gastric cavity more specialized • Four gastric pouches • Gastric filaments • Radial canals • Ring canal

  20. Class: Cubozoa • Primarly medusa form • Small 2 to 3 cm • Bells are almost square • Stings are often fatal • Pendalium- base of the tentacle has a flattened tough blade

  21. Class Anthozoa: “flower animals”” • Polyps only • All marine • Sea anemones and hard corals • Form symbiotic relationships with fish • Fish get protection • Anemone gets cleaned off (sediment) and fish lures in other fish

  22. Anthozoa anatomy • Gastravascular cavity divided into six radial chamber by six pairs of septa or mesenteries

  23. Class Anthozoa: Corals • Live in calcareous cups they have secreted • Epidermis secretes limy skeletal cup at base which provides protection (organism may contract back into the skeletal cup)

  24. Reefs • 60% are threatened • Second most diverse places on the planet • Types of reefs • Fringing reef • Close to landmass with either no lagoon or a narrow lagoon between reef and shore • Atoll • Reefs that encircle a lagoon but not an island • Slope steeply into deep water at the sea edge • Barrier reef • Runs parallel to shore and has a wider and deeper lagoon that a fringing reef

  25. Economic Importance • Food for other animals • http://www.youtube.com/watch?v=DmNOsOm0JiE • Symbiotic relationships • Live on crab shells and provide protection (mutualistic relationship) • Toxins may be sequestered by others (parasitic) http://video.nationalgeographic.com/video/animals/invertebrates-animals/other-invertebrates/weirdest-nudibranch/ • Rarely food for people • Coral Reefs

  26. Effect on Humans • Mostly non life threatening • Exceptions • Portuguese Man-of-war • Box jelly • Treatment • White vinegar • urine

  27. Coral Reefs Economic Importance • Fish and other animals associated with reefs provide food for humans • Tourist attractions • Serve as a breaker for waves • Coral jewelry and ornaments • Building materials

  28. Movies • Worlds Deadliest Jellyfish • http://www.youtube.com/watch?v=zbdo2KcaG1M • Secrets of jellyfish, killers and life savers • http://www.youtube.com/watch?v=VHTmRwwKb1k

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