Platyhelminthes Nematoda Annelida Molluscs

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PlatyhelminthesNematodaAnnelidaMolluscs

• Worms and other fun things!
• ?

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Phylum Platyhelminthes- Flatworms

• Bilateral symmetry
• Acoelomate
• Gastrovascular cavity with one opening
• More advanced nervous system than
  Porifera/Cnidaria
• Some respire (breathe) directly through skin

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Platyhelminthes
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Many flatworms are hermaphroditic
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Platyhelminthes tapeworm
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Platyhelminthes flukes
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Nematoda (Roundworms)

• NON-segmented!!
• Pseudocoelomate
• Complete digestive tract (two openings)
• Many are parasitic
• Abundant (as many as 90,000 roundworms in one
  rotten apple!)
• C. elegans first multicellular animal to have
  its complete DNA sequenced

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Life cycle of Nematode animal parasite
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Annelida (Segmented worms)

• Coelomate
• Segmented
• Complete digestive tract
• Closed circulatory system (earthworms have 5
  hearts)
• Paired setae (bristles) for movement
• Cephalization

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Earthworms - Oligochaetes
Earthworm
Earthworm moving
True body cavities and segmentation are important
evolutionary adaptations!!
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Marine worms - Polychaetes

• Many setae brushlike structures
• Some have tentacles and eyes

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Annelida - Polychaetes
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Leeches - Hirudinea

• No or very few setae
• Mostly parasitic, one-fourth carnivorous

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Annelida Hirudinea
Waiting for a host
Medicinal uses
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Phylum Mollusca Classes

• Polyplacophora (chitons)
• Gastropoda- snails, slugs, nudibranchs
• Bivalvia- clams, oysters, mussels
• Cephalopoda- octopus, squid

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Mollusca General Characteristics

• Coelomate (true body cavity)
• Soft body usually covered by a shell
• Bilaterally symmetrical
• Muscular foot
• Well-developed body organs in a visceral mass
  above the foot.
• Sexes separate (usually)

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A typical Mollusk
Viscera
Mantle
Lungs/Gills
Foot
Radula
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Polyplacophora - Chitons

• Lives in rocky-intertidal region
• Has series of plates for a shell.
• It is an herbivore (except for one species)

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Gastropoda (stomach foot) Snails, slugs,
nudibranchs, and sea hares

• Marine and terrestrial
• Herbivores and predators
• Has a radula
• 2nd largest class in animal kingdom
• Hard shell (most)
• Well-developed head with tentacles

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Gastropoda - variety
Nudibranchs

• Limpet (top)
• Conch (bottom)

Cowrie (left), Abalone (above)
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Gastropoda Cone snail (deadly!)
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Bivalvia Clams, oysters, mussels, scallops

• Live in sediments or attached to rocks (some bore
  into rocks)
• Shell has two parts (valves) which are hinged
• Filter feeders no radula

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Cephalopods (head foot) Octopi, squids,
cuttlefishes, nautiluses

• Predators
• Foot is separated into tentacles most have 8,
  nautiluses have up to 90
• Shell - absent in octopi, internal in squids and
  cuttlefish, and present in nautiluses

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Cephalopods variety