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Explore the fascinating characteristics, life cycles, and diverse forms of Phylum Cnidaria, including Hydrozoa, Scyphozoa, Cubozoa. Learn about their radial symmetry, different body forms, and unique features like nematocysts and nerve nets in this informative guide.
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Phylum Cnidaria Class Anthozoa Class Hydrozoa Class Scyphozoa Class Cubozoa Corals Anemones Hydra Portuguese Man-Of-War Stinging Limu Fire Coral True jellyfish Box jellies Sea wasps
Characteristics of Phylum Cnidaria • radial symmetry • blind sac gut (= coelenteron or gastrovascular cavity) • diploblastic with mesoglea • polyp and medusa body forms • nematocysts (= specialized stinging capsules) • nerve net • lack excretory, circulatory & respiratory systems • complex life cycle • many colonial forms exhibiting polymorphism
oral Radial Symmetry Polyp aboral
Radial Symmetry JellyfishPhylum Cnidaria Medusa
Diploblastic- two germ layers Phylum Cnidaria
Nematocyst Picture Nematocyst
More Nematocysts http://www.youtube.com/watch?NR=1&v=-Tp38DUjUnM&feature=endscreen
The Cnidarian Life Cycle The Cnidarian Life Cycle
Coloniality CoralPhylum Cnidaria
Class Hydrozoa (Gr. hydra, water serpent) • polyps and medusa stage, although polyp stage is dominant. • gut cavity of polyp is simple, lacking a pharynx and not divided by mesenteries. • tetramerous (four-part) radial symmetry. • gonads are ectodermal (found in the epidermis). • medusa stage may possess specialized balance organs called statocysts and photosensitive organs called ocelli. • solitary or colonials; some colonial forms highly polymorphic. • includes hydroids (“stinging limu”), fire coral, pink coral, and siphonophores.
The Cnidarian Life Cycle The Hydrozoan Life Cycle
Class Scyphozoa (Gr. skyphos, cup) • medusae stage dominate. • polyp stage (scyphistoma) goes through strobilization to produce young medusa. • bell margin lacks a velum. • tetramerous (= four-part) radial symmetry. • gut divided into a complex system of radial canals. • some with a simple single mouth, but many with thousands of microscopic “mouths” at the ends of oral arms. • gonads endodermal (found in the gastrodermis). • specialized sense organs called rhopalia with ocelli & statocysts . • includes some 200 marine species. • "true" sea jellies.
scyphistoma strobila Scyphozoan Life Cycle
Class Cubozoa (Gr. kybos, a cube) • medusae dominate stage. • polyp stage develops directly into medusa. • bell margin with a velarium. • tetramerous (= four-part) radial symmetry; bell cube-shaped with tentacles arising from each corner. • gonads endodermal (found in the gastrodermis). • specialized sense organs called rhopalia with ocelli & statocysts . • includes some 15 marine species. • includes box jellies and sea wasps.
Seawasp Box Jellies
Class Anthozoa (Gr. anthos, flower) • Polyp stage only • Blind sac gut • mesenteries radiate inwards from the body wall • gonads endodermal, borne on the mesenteries • hexamerous (6-part) or octamerous (8-part) radial symmetry or biradial • sea anemones, “true” stony corals, sea fans, sea pens, organ pipe coral, precious black coral, & zoanthids
Subclass Zoantharia Order Actinaria Sea Anemones
Subclass Hexacorallia Order Zoanthidae • No hard skeleton • May be tough and leathery • Shallow water forms • Encrusting forms • Some with zooxanthellae • Polyp stage only
Subclass Hexacorallia Order Antipatheria Black Coral & Wire Coral Black coral Wire coral
Subclass Hexacorallia Order Scleractinia “True” Stony Corals Hermatypic- reef building, zooxanthellae • Common species: • Acroporidae- table • Acroporidea- rice • Agariciidae- flat lobe, corrugated • Faviidae- crust, ocellated • Fungiidae- humpback, mushroom • Pocilloporidae- lace, antler, cauliflower • Poritidae- finger, lobe, plate
“True” Stony Corals lobe finger mushroom Porites rus
Octocorals Sea pen