Marb 435 1st Edition Lecture 5Current Lecture: CnidariaCnidarians 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 animalNeed 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 tentaclesAsexual reproductiono Great capacity to heal and regenerateo Mechanisms of cloning: budding or fissiono Cloning is more common in polyps than in medusaeSexual Reproductiono Generally gonochorico Germ cells originate in the gastrodermiso External fertilizationo Zygote develops into planulalarvaClassification:Classes: Scyphozoa, Cubazoa, Hydrozoa, Staurozoa, AnthozoaSubclasses: Hexocorallia, Octocorallia.Rhopalia- Complex sensory organsConsist of, statocyst, mechanoreceptor, chemoreceptor, photoreceptor(cubozoans: box jellies have rhopalia very complex lens eyes that can probably form images)Terms to know:1. Zooids- individuals that form colonies2. Polymorphic- when individual zooids in a colony perform different functions3. Pneumatophores- flotation devices used my siphonophores4. Nectophores- propel the siphonophore colony by jet propulsion5. Bracts- defend the colony6. Hydrocorals- not true corals, but they secrete a calcareous skeleton. Example includes fire coral.7. Siphonoglyphs- cilated groves in pharynx8. Hexamerous- septa occurs in multiples of
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