Mollusca

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• Mollusca
• Bivalvia
• Laterally compressed
• Two-valved shell
• No head
• No radula
• Some have muscular foot for burrowing (How?)
• Gills used for suspension feeding (active)
  respiration
• Water enters and leaves through siphons
• Some anchor to substrate with byssal threads
• Largest mollusk (giant clam)
• Shipworms (boring use shells as rasps)
• Common fouling organisms
• Oysters Produce pearls
• Scallops Swim!

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• Mollusca
• Bivalvia
• Laterally compressed
• Two-valved shell
• No head
• No radula
• Some have muscular foot for burrowing (How?)
• Gills used for suspension feeding (active)
  respiration
• Water enters and leaves through siphons
• Some anchor to substrate with byssal threads
• Largest mollusk (giant clam)
• Shipworms (boring use shells as rasps)
• Common fouling organisms
• Oysters Produce pearls
• Scallops Blue eyes, Swim!

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• Mollusca
• Cephalopoda
• Octopuses Eight arms, no shell Cryptic
• Squids Shell reduced to pen made of chitin
• Cuttlefishes Carbonate shell
• Nautilus Shell with chambers
• Highly mobile predators
• Large eyes
• Complex nervous system
• Closed circulatory system
• Shell reduced or absent (Why?)
• Type of shell affects prey selection
• Foot modified as arms and tentacles bearing
  suckers
• Siphon Directs water released from mantle
  cavity
• Ink sac for defense

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Fig. 7.24
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• Mollusca
• Polyplacophora (Chitons)
• Mostly graze algae on rocky shorelines
• Occupy home scar when not foraging
• Scaphopoda (Tooth shells)
• Predators on foraminifera and juvenile bivalves
• Most common in deep water
• Monoplacophora
• Rediscovered in 1952
• Some repeated organs (segmentation?)
• Possible indication of relationship to Annelida

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• Arthropoda
• Most species of any phylum (1 million)
• Ubiquitous
• Segmented, bilaterally symmetrical body
• Jointed appendages
• Exoskeleton made of chitin
• Growth requires molting
• Crustacea (subphylum)
• Contains majority of marine arthropod species
• 150,000 described species
• Exoskeleton often hardened with CaCO3
• Gills two pairs of antennae (sensory)

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• Arthropoda
• Copepoda (Copepods)
• Extremely abundant and important plankton
• Among most abundant animals on earth
• Benthic forms also important
• Important primary consumers of phytoplankton
• Some parasitic forms

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Fig. 7.28
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Herbivorous vs. Predatory Copepod
Fig. 15.7