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Annelids

Annelids. Polychaeta Oligochaeta Hirudinea. Classification. Body Plan. Body Plan – Key Features. Segmented (metamers) Septa separate coelem at each segment Longitudinal and circular muscles Peristaltic movement Closed circulatory system Cerebral ganglia with two nerve cords

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Annelids

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  1. Annelids Polychaeta Oligochaeta Hirudinea

  2. Classification

  3. Body Plan

  4. Body Plan – Key Features • Segmented (metamers) • Septa separate coelem at each segment • Longitudinal and circular muscles • Peristaltic movement • Closed circulatory system • Cerebral ganglia with two nerve cords • Advanced nephridia

  5. Class Polychaeta • Complex head structures • Eyes • Tentacles • Jaws • Filtering devices • Parapodia – leg-like appendages at each segment • Setae – chitinous fibers

  6. Free Swimming PredatorNereis virens • Parapodia used to swim and burrow • Chitinous jaws to capture prey • Eye spots and small tentacle • Gas exchange at parapodia

  7. Nereis virens Head

  8. Nereis virens Cross Section

  9. Tentacle Feeder • Burrow in sand or mud • Tentacles • Covered with mucous and cilia • Retracted to collect food or for protection • Gills present for gas exchange

  10. Tentacle Feeder(Amphitrite)

  11. Ciliary Feeder • Burrow in sand or mud • Epithelia secretes leathery tube • Tentacles • Covered with mucous and cilia • Grooved for sorting different sized particles • Can be retracted for protection • Tentacles used for gas exchange

  12. Ciliary Feeder(Sabella)

  13. Tube Feeder • Epithelia often secretes parchment-like tube • Parapodia “fans” or peristaltic motion moves water through tube • Mucous captures food

  14. Tube Feeder - Chaetopterus

  15. Tube Feeder – Arenicola

  16. Class Oligochaeta • Examples • Lumbricus terrestris (earthworm) • Tubifex worms

  17. Longitudinal Anatomy

  18. Circulatory System • Closed – capillary network for exchange • Dorsal and ventral blood vessels • Five aortic arches for pumping (heart) • Contains amoeboid cells and dissolved hemoglobin • Coelomic fluid – also involved in circulation

  19. Cross Sectional Anatomy

  20. Nephridia • Found in each segment • Nephrostome crosses into next segment • Cilliated funnel to draw in fluid • Water and nutrient reabsorbed • Function similar to kidney

  21. Nephridia

  22. Reproduction • Hermaphroditic – exchange sperm • Clitellum • Attach during mating • Secretes cocoon

  23. Class Hirudinea • Leeches • Anterior and posterior sucker • No, setae, septa • Coelom filled with muscle and connective tissue • Reproduction similar to Oligochaeta • Many lack enzymes for digestion – rely on bacteria

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