Cnidarian Diversity Phylum Cnidaria Class Class Class Class Anthozoa Hydrozoa Scyphozoa Cubozoa Corals Hydra True jellyfish Box jellies Anemones Portuguese Man-Of-War Sea wasps Stinging Limu Fire 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 • 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 –aka Portuguese man of War The Cnidarian Life Cycle The Hydrozoan Life Cycle Hydrozoan Colony Hydrozoan Medusa Fire Coral By-the-Wind-Sailor A Floating Colony of Polyps Coloniality Man-of-War Phylum Cnidaria Close Up of a Portuguese Man-Of-War Class Scyphozoa (Gr. skyphos, cup) • life cycle with both polyps and medusa, but medusa 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. Scyphozoan Life Cycle strobila scyphistoma ephyra planula adult medusa gametes scyphistoma strobila Sea Jellies Moon Jelly Anatomy 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 Box Jelly Anatomy 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 Sea Anemone Anatomy Subclass Hexacorallia Order Zoanthidae Soft Corals • No hard skeleton • May be tough and leathery • Shallow water forms • Encrusting forms • Some with zooxanthellae • Polyp stage only Subclass Hexacorallia Order Scleractinia “True” Stony Corals Hermatypic- reef building, zooxanthellae Common species come in many different forms. These are real Reef Corals. “True” Stony Corals lobe finger mushroom Porites rus.