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Phylum Cnidaria BIO 2215 Oklahoma City Community College Dennis Anderson 1 Phylum Cnidaria • Radial symmetry • Mouth at oral end surrounded by tentacles. • One opening into and out of gastrovascular cavity. • Cnidocytes that discharge pneumatocysts • Two body forms – Polyp – Medusa • Two germ layers • Nerve net 2 Radial symmetry 3 Mouth and Tentacles 4 Fig. 13.2 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Generalized Cnidarian Life Cycle 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cnidocyte Structure and Nematocyst Discharge 7 Diploblastic - 2 germ layers – Epidermis - outer covering (ectoderm) – Mesoglea - middle non-living jelly-like layer – Gastrodermis - lines gastrovascular cavity (endoderm) 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cnidarian Body Wall 9 Nervous System • Nerve cells, arranged in a nerve net. 10 Class Hydrozoa • Freshwater & marine. • Cnidocytes present only on epidermis. • Medusa (if present) with a muscular velum. • Mesoglea without ameboid cells. • Asexual reproduction by budding. • Sexual reproduction via gametes produced by epidermis & released into water. 11 Class Hydrozoa • • • • Hydra Obelia Gonionemus Physalia 12 Class Hydrozoa Hydra Encapsulated embryo Ovaries Budding Spermaries Sexual cycle Asexual cycle 13 Hydra Body Wall Gastrovascular cavity Gastrodermis Mesoglea Epidermis 14 Fig. 13.9 15 Obelia 16 Obelia Gonangium Medusa bud Medusae 17 Class Hydrozoa Gonionemus 18 Class Hydrozoa Gonionemus Velum 19 Class Hydrozoa Physalia 20 Class Scyphozoa • Tentacles up to 70 meters in length • Cnidocytes present in gastrodermis & epidermis • Thick mesoglea contains ameboid cells • Gametes produced by gastrodermis • All marine 21 Class Scyphozoa Aurelia 22 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Aurelia Life History 23 Fig. 13.18 24 Planula Larva Ciliated larva than can swim to a new location 25 Aurelia Mesoglea Eggs Gastrovascular cavity Mouth 26 Aurelia Oral arm Gastric pouch Mouth Tentacles 27 Class Cubozoa • Medusa dominant & cuboid • Tentacles arise at four corners from blade-like pendalium. • All marine • Strong swimmers which prey primarily on fish • Stings of some may be fatal within minutes to humans. 28 Class Cubozoa Gonad Pedalium Tentacle 29 Class Cubozoa Chironex Sea Wasp 30 Class Anthozoa • Medusa stage absent • Solitary or colonial • Some produce protective skeletons • Gastrovascular cavity subdivided by at least 8 mesenteries • Cnidocytes on mesenteries • Mesoglea contains ameboid cells • All Marine 31 Class Anthozoa Sea Anemone 32 Class Anthrozoa Metridium Tentacles Mouth Pharynx Septum Gastrovascular cavity 33 Symbiosis 34 Class Anthozoa Corals • Protective skeleton of calcium carbonate • Polyp retracts when not feeding 35 Zooxanthellae • Photosynthetic dinoflagellates (brown) • Live in corals • Provide nutrients for coral by photosynthesis • Mutualism 36 Corals Colony of interconnected polyps 37 Class Anothozoa Meandrina Brain Coral 38 Class Anothozoa Gorgonia Sea Fan 39 Class Anothozoa Tubipora Pipe Organ Coral 40 Class Anothozoa Actinodiscus Mushroom Coral 41 Class Anothozoa Acropora Staghorn Coral 42 Coral Reefs • • • Formed over thousands of years from successive layers of coral skeleton deposits (calcium carbonate forms underwater mountains of coral animal skeletons) The underwater equivalent of the amazon jungle- very high species diversity and biomass Reefs contain sponges, colonial hydrozoans, anemones, many varieties of coral, fish, many types of worms we’ve not discussed, not to mention bryozoans, ctenophores, protists, bacteria, etc etc.. 43 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Coral Reef Ecosystem Photo © McGraw-Hill Higher Education, Barry Barker, Photographer 44 Cladogram of Cnidaria Anthozoa Scyphozoa Hydrozoa Cubozoa Medusa cuboidal Loss of medusa Polyp stage reduced Septa divide gastrovascular cavity Radial symmetry, cnidocytes, planula larva 45 The End 46
