PHYLUM: CNIDARIA Classes of Cnidaria Class Class Class Class Hydrozoa (e.g., Hydra, Obelia) Scyphozoa (e.g., Aurelia) Cubozoa (e.g., cube jellies) Anthozoa (anemones and corals) Subclass Hexacorallia (sea anemones, hard corals) Subclass Octocarallia (sof corals) General Characteristics Entirely aquatic; mostly marine, but with a few freshwater species; may be solitary or colonial Metazoan, with true tissues. Diploblastic – two germ layers outer cell layer known as ectoderm (epidermis), inner cell layer known as endoderm (=gastrodermis), with a non-cellular mesoglea between. General Characteristics The internal body space (gastrovascular cavity) lined with gastrodermis has a mouth, but no anus (incomplete digestive tract) Possess cnidocytes with special cell organelles - nematocysts, used for defense and offense General Characteristics cont. Phylum exhibits polymorphism Metagenesis- alternation of generation Polyp (often sessile) and the medusa (free swimming). The polyp stage reproduce asexually, while the medusa stage usually reproduces sexually Reproduction is asexual by budding and/or sexual, producing a ciliated planula larva Figure 13.02 Two general body forms Class Hydrozoa solitary or colonial alternation of asexual polyps and sexual medusae Figure 13.09 Life Cycle of Hydra SEXUAL REPRODUCTION ASEXUAL REPRODUCTION Hydra with Bud Ovary Bud Hydra with Gonads Testes Hydra c.s. Gastrovascular cavity Epidermis Mesoglea Gastrodermis Figure 13.09 Obelia Life Cycle Obelia - Medusa Gonad Tentacle Gastrovascular cavity Obelia – Hydroid colony Gastrozoids = Hydranth Gonozoids = Gonangium Obelia – Hydroid Colony Gonozooid Hydrozooid Gonionemus Gonad Physalia – Portuguese Man-O-War - a colony, not an individual It is not a jellyfish!! Class Scyphozoa True Jellyfishes polyp stage reduced or absent bell-shaped medusae margin of bell with eight notches which are provided with sense organs all marine Aurelia - Medusa Aurelia - Planula larva Aurelia - Scyphistoma Aurelia - Strobila Aurelia - Ephyra Class – Anthozoa Sea Anemones and Corals all species occur as polyps only, no medusae; gastrovascular cavity partitioned by at least eight septa with nematocysts Solitary or colonial all marine. Some Hydrozoans Figure 13.07 0022.jpg Figure 13.15a Figure 13.15b Some Scyphozoans Jellyfishes Figure 13.16 Figure 13.17 Some Anthozoans Sea Anemones Figure 13.25 Figure 13.29 Corals Figure 13.32 Figure 13.33a Figure 13.33b Figure 13.28 0039.jpg 0041.jpg 0047.jpg 0048.jpg Figure 13.26b Figure 13.26c 0049.jpg 0050.jpg Phylum Ctenophora The Combjellies General Characteristics Biradial symmetry Eight rows of comb plates Tentacles possess colloblasts Triploblastic (three cell or germ layers) Mesoglea (loose mesenchyme) is jelly-like material strews with fibers and amebocytes and contains true muscle cells Aboral sense organ (statocyst) Digestive system: mouth, pharynx, stomach, branched canals and anal pore Monoecious, with both eggs and sperm produced from endodermal lining of digestive canals beneath comb plates Figure 13.36 Figure 13.36a Figure 13.38 Figure 13.38a Figure 13.38b Figure 13.35 0002.jpg