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
Class Anthozoa Subclass Hexacorallia Subclass Alyconaria Sea fans Sea whips Sea pens Organ pipe coral Precious gold coral Order Zoanthidae Order Actinaria Order Scleractinia Order Antipatharia Zoanthids Sea anemones Stony corals Precious black coral Wire coral
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
Coloniality Man-of-WarPhylum Cnidaria
Close Up of a Portuguese Man-Of-War
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 strobila scyphistoma ephyra planula adult medusa gametes
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