Today

1
Todays 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

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Class Polychaeta

• Mostly marine
• Parapodia
• Cuticle
• 1st segment prostomium
• 2nd segment peristomium

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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

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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

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Oligochaete Locomotion

• Use circular and longitudinal muscles
• Can use setae as anchors
• Use hydrostatic pressure

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Oligochaete Feeding

• Scavengers and/or detritovores
• Path of food
• Mouth
• Pharynx
• Crop
• Gizzard
• Stomach
• Intestine

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Other Oligochaete Systems

• Most ganglia fused
• Reduced eyes
• Sensitive to chemical or mechanical stimuli
• Use metanephridia for excretion
• Chloragogen tissue

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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

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Hirudinean Feeding

• Many carnivorous
• Small invertebrates
• Body fluids
• Mouth in the anterior sucker
• Produce hirudin anticoagulant

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Other Hirudinea Systems

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

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Hirudinea Reproduction

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