Nematoda

1

• Nematoda
• Free living and parasitic forms
• Cosmopolitan/Ubiquitous
• Mostly in sediments (free living) or hosts
  (parasitic)
• Common in fine muds
• Organic rich areas
• Described species 12,000
• May be up to 500,000 species total!
• Extremely abundant!!
• Up to hundreds of individuals per ml of sediment
• 90,000 in one rotting apple (not marine)
• Hydrostatic skeleton
• Longitudinal muscles only
• Move by whipping back and forth

2

• Other Worms
• Sipuncula (Peanut worms)
• Exclusively marine (250 species)
• Most common in shallow water
• Unsegmented bodies up to 35 cm long
• Studded introvert used for locomotion
• Cryptic
• Burrow in sediments or hide in shelters
• Deposit feeders
• Consume detritus and microbes

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• Other Worms
• Sipuncula (Peanut worms)
• Exclusively marine (250 species)
• Most common in shallow water
• Unsegmented bodies up to 35 cm long
• Studded introvert used for locomotion
• Cryptic
• Burrow in sediments or hide in shelters
• Deposit feeders
• Consume detritus and microbes

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Fig. 7.3
6

• Other Worms
• Echiura (Spoon worms)
• Exclusively marine (150 species)
• Deposit feeders
• Feed with non-retractable proboscis
• Live in burrows
• U-shaped or L-shaped
• Typically small but may get large in deep sea

7

• Other Worms
• Pogonophora (Beard worms)
• Long, thin worms (135 species)
• Most common in deep sea
• No mouth or gut
• Not parasitic
• Anterior end of body is tuft of up to several
  thousand tentacles
• Tentacles absorb dissolved nutrients
• Symbiotic bacteria utilize nutrients to
  manufacture food
• Vestimentifera
• Large deep-sea animals
• Found at many hydrothermal vents

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Fig. 7.17
9

• Other Worms
• Pogonophora (Beard worms)
• Long, thin worms (135 species)
• Most common in deep sea
• No mouth or gut
• Not parasitic
• Anterior end of body is tuft of up to several
  thousand tentacles
• Tentacles absorb dissolved nutrients
• Symbiotic bacteria utilize nutrients to
  manufacture food
• Vestimentifera
• Large deep-sea animals
• Found at many hydrothermal vents

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11

• Annelida
• Segmented worms
• Body composed of repeated segments
• Gut runs through all segments in body cavity
  (coelom)
• Coelom filled with fluid hydrostatic skeleton
• Longitudinal and radial muscles
• Efficient locomotion and burrowing
• More than 15,000 species
• Cosmopolitan

12

• Annelida
• Polychaeta
• 10,000 species (mostly marine)
• Body segments bear pairs of parapodia
• Parapodia used for locomotion, feeding
• Often tipped with setae
• Closed circulatory system
• Efficient transport of blood, gases
• Gas exchange
• Small species exchange gases across body wall
• Large species have gills for gas exchange
• Highly vascularized with capillaries and thin
  body walls

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Fig. 7.15
14

• Annelida
• Polychaeta
• Spawning Palolo worm
• Larva Trochophore
• Band of cilia around body tuft on apex
• Same larval stage in Mollusca, Echiura, Sipuncula
• Diverse lifestyles
• Free-living predators
• Often well-developed eyes and sense organs, jaws
• Burrowing deposit feeders
• Burrowing suspension feeders
• Tube building suspension feeders
• Tubes may be calcium carbonate, agglutinated or
  parchment
• Solitary
• Colonial

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• Annelida
• Polychaeta
• Larva Trochophore
• Band of cilia around body tuft on apex
• Same larval stage in Mollusca, Echiura, Sipuncula
• Diverse lifestyles
• Free-living predators
• Often well-developed eyes and sense organs, jaws
• Burrowing deposit feeders
• Burrowing suspension feeders
• Tube building suspension feeders
• Tubes may be calcium carbonate, agglutinated or
  parchment
• Solitary
• Colonial

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• Annelida
• Polychaeta
• Larva Trochophore
• Band of cilia around body tuft on apex
• Same larval stage in Mollusca, Echiura, Sipuncula
• Diverse lifestyles
• Free-living predators
• Often well-developed eyes and sense organs, jaws
• Burrowing deposit feeders
• Burrowing suspension feeders
• Tube building suspension feeders
• Tubes may be calcium carbonate, agglutinated or
  parchment
• Solitary
• Colonial