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Today’s Objectives

Today’s Objectives. Explore the diversity, success, body plans, organ systems and economic importance of phylum Annelida. Annelida. Segmented Worms. Main Characteristics. Bilateral symmetry Metameric Tagmatization Protostomes Triploblastic Setae Closed Circulatory System

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Today’s Objectives

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  1. Today’s Objectives • Explore the diversity, success, body plans, organ systems and economic importance of phylum Annelida.

  2. Annelida Segmented Worms

  3. Main Characteristics • Bilateral symmetry • Metameric • Tagmatization • Protostomes • Triploblastic • Setae • Closed Circulatory System • Ganglia and Nerve Cords • Metanephridia

  4. Classes of Annelids • Polychaeta – Nereis, Arenicola • Oligochaeta – Lumbricus, Tubifex • Hirudinea - Hirudo

  5. Class Polychaeta • Mostly marine • Parapodia • Cuticle • 1st segment – prostomium • 2nd segment – peristomium

  6. Polychaeta Feeding • Most carnivorous • Some have venom • Gut is straight tube • Some are detritovores • Extract nutrition from sediment (or soil) • Gut has crop and gizzard • Many are filter feeders • Some can get food by diffusion

  7. Other polychaete Systems • Respiration by diffusion • 2-4 pairs of eyes on/near prostomium • Chemoreceptors • Statocysts • Metanephridium for excretion • Chloragogen tissue for protein metabolism

  8. Polychaete Reproduction • Can regenerate • Asexual reproduction • Budding • Fission • Sexual reproduction • Most fertilization external • Can have alternation of generations • Epitoke (sexual) vs. Atoke (asexual)

  9. Oligochaeta • Terrestrial, freshwater, some marine • Have a clitellum • For mucus secretion • Used in copulation • Used to form cocoons • No parapodia • Few setae

  10. Oligochaete Locomotion • Use circular and longitudinal muscles • Can use setae as anchors • Use hydrostatic pressure

  11. Oligochaete Feeding • Scavengers and/or detritovores • Path of food • Mouth • Pharynx • Crop • Gizzard • Stomach • Intestine

  12. Other Oligochaete Systems • Most ganglia fused • Reduced eyes • Sensitive to chemical or mechanical stimuli • Use metanephridia for excretion • Chloragogen tissue

  13. Oligochaete Reproduction • Hermaphroditic • Must line up clitella • Held together by mucus sheath • Cocoon formed • Fertilization occurs here • No larval stages • Some freshwater species asexual

  14. Hirudinea • Terrestrial, freshwater or marine • No parapodia • Secondary annuli on segments • Circular, longitudinal and oblique muscle layers

  15. Hirudinean Feeding • Many carnivorous • Small invertebrates • Body fluids • Mouth in the anterior sucker • Produce “hirudin” – anticoagulant

  16. Other Hirudinea Systems • Gas exchange by diffusion • Nervous system • Photoreceptors • Can sense temperature • Sensory papillae • 10-17 pairs of metanephridia for waste • Chloragogen tissue

  17. Hirudinea Reproduction • All monecious • All sexually reproducing • Have a penis for sperm transfer • Clitellum seen during breeding season • No larval stages

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