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
General Characteristics of Cnidaria • Stinging cells • Two stages in life cycle (polyp & medusa) • Blind sack gut • Radial symmetry • Diploblastic • Hydrostatic skeleton • Nerve net • Many colonial, some solitary forms
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) • life cycle with both polyps and medusae, but medusae dominate with polyp stage reduced or absent. • 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) • polyps and medusae stages, but medusae dominate with polyp stage reduced. • 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) • lack medusa stage entirely (polyp forms only) • mouth with a tubular pharynx that projects inward into the gut • large gut cavity divided by mesenteries that radiate inwards from the body wall • gonads endodermal, borne on the mesenteries • hexamerous (6-part) or octamerous (8-part) radial symmetry or biradial (modified radial symmetry that limits the number of planes that can divide the body into equal halves • includes 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
Subclass Alyconaria Octocorals • 8 branched tentacles surrounding the mouth • Both hard and soft forms exist • Ahermatypic- non reef building, no photosynthesis • Five Orders found in Hawaii: • Stolonifera • Pennatulacea (sea pens) • Alcyonacea (soft corals) • Telestacae (snowflake corals) • Gorgonacea (sea fans)
Octocorals Sea pen