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Phylum Cnidaria (formerly Coelenterata)

Phylum Cnidaria (formerly Coelenterata). G: stinging thread bearing. The Hydra. Powers of regeneration stem from omnipotent cells. Evolutionary Relationships. Phylum Cnidaria. All have nematocysts (cnidae) Have radial symmetry 2 layers (epidermis and gastrodermis)

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Phylum Cnidaria (formerly Coelenterata)

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  1. Phylum Cnidaria(formerly Coelenterata) G: stinging thread bearing

  2. The Hydra • Powers of regeneration stem from omnipotent cells

  3. Evolutionary Relationships

  4. Phylum Cnidaria • All have nematocysts (cnidae) • Have radial symmetry • 2 layers (epidermis and gastrodermis) • Mesoglea between epidermis and gastrodemrmis is a non-living layer • All have tentacles surrounding the mouth and only a single opening to the digestive system

  5. Phylum Cnidaria • Body Plan: medusa and polyp • Planula larvae in the life cycle • Have muscles and nerves • Muscles are not true muscles—epitheliomuscular cells

  6. Life Cycle of a Cnidaria

  7. Cnidae • Are organelles secreted from cnidoblasts or nematocysts • Each cnida can be discharged only once • Mechanism of expulsion currently unknown

  8. Class Scyphozoa(Asexual reproduction by strobilation (budding)) • The true jellies • Monoecious • Sperm+egg= planula Manubrium - muscular cylinder that ends in the mouth

  9. Class Scyphozoa

  10. Class Cubozoa(medusa w boxlike body; rhopalia with complex, lensed eyes) • Box jellyfish/ seawasp (cubomedusae) • Restricted to tropical and subtropical waters • Most derived cnidarians Chironex fleckeri

  11. Jellyfish Emergency • Pour vinegar over affected part, NEVER alcohol or water • Children must be brought to the hospital ASAP for medical treatment

  12. Class Hydrozoa • Polyp form predominates • Portuguese man of war • Hydrocorals– very much like corals

  13. Class Hydrozoa • Order Hydroidea (hydra) • Order Siphonophora • Portuguese man-o-war Physalia sp. • Floating colony of polymorphic hydrozoans • nectophores,phyllozooids, gastrozooids, gonozooids, dactylozooids • Order Hydrocorallina

  14. Class Anthozoa(reef-building corals, anemones, sea fans, sea pansies) • Absence of medusa • Sea anemones and corals • 70% of all cnidarian species • Subclass Hexacorallia • Subclass Octocorallia • Coral wars Anatomy of a polyp (Source: NOAA)

  15. Class Anthozoa • Coral spawning 4 days after the new moon in the summer

  16. Subclass Hexacorallia • Can be ahermatypic or hermatypic (reef-building corals) • Endosymbiont photosynthetic dinoflagellates called zooxanthellae (Symbiodinium) play an important role in coral growth. • The symbiosis is quite fragile and can be thrown off balance by stressors in the environment.

  17. Subclass Octocorallia • Sea fans, seawhips (gorgonians), pipe corals • Brain corals are also octocorals

  18. Distribution of coral reefs

  19. The Coral Triangle

  20. Coral Reefs • Corals in a reef are not stationary—there is a war for space going on all the time. • The complex interactions and many micro habitats in a coral reef are key to its high species diversity. • This ecosystem is being threatened by pollution, ocean acidification, and bleaching higher sea surface temperatures.

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