Phylum Echiura

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Phylum Echiura Phylum Sipuncula Chapter 14
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Phylum Echiura

• coelomate, protostomous, bilateral
• schizocoelous coelom formation
• no segmentation
• metanephridia
• closed circulatory system
• simple nervous system
• non-retractable oral proboscis
• trochophore larva
• found in brackish marine waters

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Echiuran body plan functions

• anterior, preoral proboscis
• groove or gutter on proboscis with cilia for
  feeding ( produce mucus to trap food)
• anterior metanephridia nephridiopores
• enlarged trunk
• complete gut with posterior anus
• trunk coelom hydrostatic skeleton
• long, coiled intestine
• gas exchange in hindgut

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Examples of echiurans
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Phylum Sipuncula

• coelomate, protostomous, bilateral
• schizocoelous coelom formation
• no segmentation
• U-shaped gut with anteriodorsal anus
• retractable anterior introvert with tentacles
  mouth
• coelom as hydrostatic skeleton, waste removal,
  circulation
• trochophore larvae
• found in marine, benthic habitats
• peanut worms

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Sipunculan body plan and functions
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Examples of sipunculans