Marb 435 1st Edition Lecture 5 Current Lecture Cnidaria Cnidarians are diploblastic meaning they have 2 germ layers endoderm and ectoderm They are radially symmetrical around the oral aboral axis They can exist in two basic forms Polyp stalked and attached Medusa bell shaped generally pelagic free swimming animal Need to know be familiar with the following diagram and the epithelial layers of the cnidarians These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Cnidocytes stinging cells of the cnidarians They are unique to cnidarians and are a combined sensory effector cell Nematocytes are the most common type of cnidocytes They discharge when prey contacts the tentacles Cnidae can paralyze prey and sometimes start digestion Cnidarian opens its mouth and licks the prey off of its tentacles Asexual reproduction o Great capacity to heal and regenerate o Mechanisms of cloning budding or fission o Cloning is more common in polyps than in medusae Sexual Reproduction o Generally gonochoric o Germ cells originate in the gastrodermis o External fertilization o Zygote develops into planulalarva Classification Classes Scyphozoa Cubazoa Hydrozoa Staurozoa Anthozoa Subclasses Hexocorallia Octocorallia Rhopalia Complex sensory organs Consist of statocyst mechanoreceptor chemoreceptor photoreceptor cubozoans box jellies have rhopalia very complex lens eyes that can probably form images Terms to know 1 2 3 4 5 6 Zooids individuals that form colonies Polymorphic when individual zooids in a colony perform different functions Pneumatophores flotation devices used my siphonophores Nectophores propel the siphonophore colony by jet propulsion Bracts defend the colony Hydrocorals not true corals but they secrete a calcareous skeleton Example includes fire coral 7 Siphonoglyphs cilated groves in pharynx 8 Hexamerous septa occurs in multiples of six
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