2 Classes of Cnidaria Class Hydrozoa (e.g., Hydra, Obelia) Class Scyphozoa (e.g., Aurelia)Class Cubozoa (e.g., cube jellies)Class Anthozoa (anemones and corals)Subclass Hexacorallia (sea anemones, hard corals)Subclass Octocarallia (sof corals)
3 General Characteristics Entirely aquatic; mostly marine, but with a few freshwater species;may be solitary or colonialMetazoan, with true tissues.Diploblastic – two germ layersouter cell layer known as ectoderm (epidermis),inner cell layer known as endoderm (=gastrodermis),with a non-cellular mesoglea between.
4 General Characteristics The internal body space (gastrovascular cavity) lined with gastrodermishas a mouth, but no anus (incomplete digestive tract)Possess cnidocytes with special cell organelles - nematocysts, used for defense and offense
5 General Characteristics cont. Phylum exhibits polymorphismMetagenesis- alternation of generationPolyp (often sessile) and the medusa (free swimming).The polyp stage reproduce asexually, while the medusa stage usually reproduces sexuallyReproduction is asexual by budding and/or sexual, producing a ciliated planula larva
61 General Characteristics Biradial symmetryEight rows of comb platesTentacles possess colloblastsTriploblastic (three cell or germ layers)Mesoglea (loose mesenchyme) is jelly-like material strews with fibers and amebocytes and contains true muscle cellsAboral sense organ (statocyst)Digestive system: mouth, pharynx, stomach, branched canals and anal poreMonoecious, with both eggs and sperm produced from endodermal lining of digestive canals beneath comb plates