Arthropoda

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• Arthropoda
• Cirripedia (Barnacles)
• Active suspension feeders (filter feeders)
• Use feathery cirri (modified swimming appendages)
• Sessile (attached to surfaces)
• Fouling organisms (boats, whales)
• Resemble mollusks superficially
• Some parasitic forms
• Simultaneous hermaphrodites
• Internal fertilization (How??)

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Fig. 7.29
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• Arthropoda
• Cirripedia (Barnacles)
• Active suspension feeders (filter feeders)
• Use feathery cirri (modified swimming appendages)
• Sessile (attached to surfaces)
• Fouling organisms (boats, whales)
• Resemble mollusks superficially
• Benthic forms also important
• Some parasitic forms
• Simultaneous hermaphrodites
• Internal fertilization (How??)

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• Arthropoda
• Amphipoda (Amphipods)
• Laterally compressed
• Generally small (lt 2 cm), but larger in deep
  ocean
• Widespread distribution
• Generally free living
• Important scavengers
• Often highly mobile
• Some sedentary forms
• Diverse lifestyles
• Brood young

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Fig. 7.30
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• Arthropoda
• Isopoda (Isopods)
• Dorsoventrally compressed
• Generally small (lt 2 cm), but larger in deep
  ocean
• Related to terrestrial pill bugs
• Widespread distribution
• Generally free living
• Important scavengers
• Often highly mobile
• Some parasitic forms
• Brood young

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• Arthropoda
• Euphausiacea (Krill)
• Laterally compressed
• Up to 10 cm long (usually smaller)
• Head and anterior segments fused to form distinct
  carapace
• Widespread distribution
• Important primary consumers and predators
• Important prey for larger consumers
• Keystone species in some ecosystems (Southern
  Ocean)
• Aggregate in schools
• May be immense (450 sq km x 200 m _at_ gt1000 m-3)

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• Arthropoda
• Decapoda (Crabs, Lobsters, Shrimps)
• Most species in Crustacea (10,000)
• Scavengers/Predators/Both
• Largest crustaceans
• Lobster gt 42 lbs
• Crab gt 10 feet tall
• Five pairs of walking legs
• First pair usually modified as claws for
  feeding/defense
• Well-developed carapace cephalothorax
• Rest of body abdomen
• Lobsters, shrimp Usually laterally compressed
• Tail/Abdomen behind thorax
• Crabs Usually dorsoventrally compressed
• Tail/Abdomen curled underneath thorax

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Fig. 7.32
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• Arthropoda
• Decapoda (Crabs, Lobsters, Shrimps)
• Most species in Crustacea (10,000)
• Scavengers/Predators/Both
• Largest crustaceans
• Lobster gt 42 lbs
• Crab gt 10 feet tall
• Five pairs of walking legs
• First pair usually modified as claws for
  feeding/defense
• Well-developed carapace cephalothorax
• Rest of body abdomen
• Lobsters, shrimp Usually laterally compressed
• Tail/Abdomen behind thorax
• Crabs Usually dorsoventrally compressed
• Tail/Abdomen curled underneath thorax

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Shediac, NB
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Fig. 7.37
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• Arthropoda
• Merostomata (Horseshoe crabs)
• Not true crabs
• Five living species
• Distinctive, horseshoe-shaped carapace
• Benthic predators/scavengers on clams and small
  invertebrates
• No jaws - Grind food with bristles on walking
  legs (must be walking to chew)

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• Arthropoda
• Pycnogonida (Sea spiders)
• Superficially resemble spiders
• Mouth at end of large proboscis (unusual)
• Carnivores
• Feed on sea anemones, hydrozoans, other soft
  inverts
• No respiratory or excretory systems
• Digestive system extends into legs

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Fig. 7.39
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• Echinodermata
• Radial symmetry (secondary)
• Bilateral symmetry in larvae
• Pentaradial symmetry in adults
• Oral/aboral - No anterior/posterior,
  dorsal/ventral
• Complete digestive tract (except Ophiuroidea)
• Endoskeleton
• Covered with layer of tissue
• Water vascular system
• Unique to echinoderms
• Tube feet extended by pressure from ampullae
• Tube feet used for locomotion, feeding, sensory
  functions
• Connected to exterior through madreporite

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Fig. 7.42
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• Echinodermata
• Asteroidea (Sea stars) - Class
• Most species have five arms (some more)
• Tube feet on oral surface in ambulacral grooves
• Endoskeleton composed of CaCO3 plates
• Flexible skeleton permits movement
• Aboral surface often covered with pedicellariae
• Small claws used for grooming surface
• Predators
• Feed on bivalves, snails, barnacles
• Pry shells of bivalve apart and insert stomach

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Heliaster helianthus
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Crown of Thorns Acanthaster planci
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• Echinodermata
• Ophiuroidea (Brittle stars, Serpent stars)
• More species (2000) than any other class
• Arms long and very flexible
• May resemble writhing snakes
• Tube feet lack suckers (used for feeding)
• Cryptic Usually not in open areas
• Scavengers/Detritivores
• Particles collected by tube feet and passed to
  mouth
• May suspension feed by climbing on taller objects
  (e.g. sponges)
• Some have eyes and produce bioluminescence
• Why??

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Amphipholis squamata