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Phylum Annelida

Phylum Annelida. Segmented Worms. Phylum Annelida. Annelids are s egmented worms. They have bodies composed of a series of fused rings. Earthworms, leeches, clam worms. Phylum Annelida. Old Traits Coelomate (body cavity) Closed circulatory system Cephalization (have a head)

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Phylum Annelida

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  1. Phylum Annelida Segmented Worms

  2. Phylum Annelida • Annelids are segmented worms. • They have bodies composed of a series of fused rings. • Earthworms, leeches, clam worms.

  3. Phylum Annelida • Old Traits • Coelomate (body cavity) • Closed circulatory system • Cephalization (have a head) • New Traits • Segmentation (body divided in segments) • Setae (Bristles) • Advanced nervous system Spirobranchus giganteusChristmas tree worm ~ 40K species of annelids

  4. Annelid Taxomony • Class Polychaeta (many segments) • Class Oligochaeta (few segments) • Class Hirudinea • Fixed # segments (34) • No bristles Hirudo medicinalis

  5. Class Polychaeta • Polychaeta (many segments) is the largest, most diverse class. • May scavengers or predators • Live mostly in the benthic ocean .

  6. Class Polychaeta • Highly specialized head regions • Antennae • Sensory organs • Feeding appendages • Paired extensions of body(parapodia) • Often tube-dwelling • Most have gills sabellid worm

  7. Class Polychaeta • Polychaetes are mostly marine and mostly benthic. • May live under rocks, burrow into sediment, or build their own tubes. • Some are planktonic.

  8. Class Polychaeta • Sedentary and errant(free-moving) forms. • Filter or deposit feeders.

  9. Polychaete Reproduction • Dioecious (separate sexes) • Trochophore larvae • Some species develop specialized segments containing gametes (epitoke) • Segments are released and gametes burst out

  10. Polychaete Asexual Reproduction • Epitokes are essentially buds • Clues to ancestral origin of segmentation • Segmentation may have been derived from incomplete budding processes

  11. Representative Polychaetes • Fanworms or Featherduster worms • Unfurl tentacular crowns to feed.

  12. Representative Polychaetes • Parchment Worms • Lives in a U-shaped tube. • Modified segments pump water through tube.

  13. Giant tube worms (Vestimentifera) trophosome Riftia pachyptila

  14. Beardworms • Discovered in 1900. • 150 species described. • Giant beardworms that live in deepwater hydrothermal vents are 3 m long and 5 cm in diameter.

  15. Oligochaetes

  16. Class Oligochaeta • Class Oligochaetaincludes earthworms and many freshwater worms.

  17. Earthworms - Nervous System and Sense Organs • Central nervous system and peripheral nerves. • The brain secrete neurohormones. • Regulate sex characteristics, and regeneration. • Lack eyes but have many photoreceptors in the epidermis. • Sensitive to light, touch, moisture, chemicals, temperature, & vibrations

  18. Earthworms - Feeding • One way digestive system • The lip digs through soil as earthworm feeds on organic matter (detritus) • Food is stored in a sac like structure (crop.) • Muscular gizzard grinds food. • Digestion and absorption occur in intestine.

  19. Earthworms - Circulation and Respiration • Blood transport food, wastes, and respiratory gases. • Blood circulates in a closed system with five main trunks running along the body. • Dorsal vessel contains valves and functions as a true heart.

  20. Earthworms - Reproduction • Earthworms are hermaphroditic – male and female organs in the same animal. • When mating, two worms are held together by mucus secreted by theclitellum.

  21. Earthworms Reproduction The development is direct without any larval forms

  22. Class Oligochaeta • Darwin wrote about earthworms. • He noted the beneficial activities of worms, aeration, moving nutrients up from subsoil, adding nitrogenous products, breakdown of organic matter in dead leaves etc. • An earthworm can ingest its own weight in soil every 24 hours.

  23. Annelid Body Plan Setae

  24. Oligochaete Anatomy

  25. Seta: a.k.a. Bristles

  26. Oligochaete Excretory System

  27. Oligochaete Development • For terrestrial oligochaetes, development is direct without any larval forms • Some aquatic oligochaetes retain a trochophore-like larval stage

  28. Common Terrestrial Oligocheates: Earthworms • Octagonal-tail worm (Dendrobaena octaedra) • Red marsh worm (Lumbricus rubellus) • Dew-worm or nightcrawler (Lumbricus terrestris) • Pink soil worm (Aporrectodea rosea) • Canadian worm (Aporrectodea tuberculata) • Pasture worm (Aporrectodea turgida) • Woodland white worm (Octolasion tyrtaeum) • Redworm (Eisenia fetida )

  29. Quick and Easy Earthworm Morphology Guide Morphology Number & location of GTs and TPs, location & shape of clitellum Ecology Location of burrows Aporrectodea turgida Lumbricus rubellus

  30. Aquatic Oligocheates

  31. Class Hirudinea

  32. Hirudo medicinalis

  33. Phylum Sipuncula • ~250 species • Trochophore larvae

  34. Sipunculan Internal Structures

  35. Phylum Echiura • ~140 species • Closed circulatory system • Trochophore larvae Echiurus sp

  36. Phylum Echiura Bonellia viridis

  37. Echiuran Anatomy

  38. Oddities • Sex determination & dimorphism in echiurans

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