Keystone Species

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• Keystone Species

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• Echinodermata
• Echinoidea (Sea urchins, Sand dollars)
• Approximately 1000 species
• Includes heart urchins, sea biscuits
• Round, rigid test with movable spines and
  pedicellariae
• Spines and tube feet used for locomotion
• Tube feet in shallow ambulacral grooves along
  outside of test
• Complete digestive system
• Mouth on bottom, anus on top
• Herbivores
• Feed on seaweeds and seagrasses (especially
  drifting) plus attached encrusting organisms
• Mouth includes Aristotles lantern

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• Echinodermata
• Holothuroidea (Sea cucumbers)
• Lack spines
• Five rows of tube feet run from mouth to anus
• Endoskeleton reduced to small calcareous spicules
  in skin
• Complete digestive system
• Respiration through respiratory trees
• Deposit and suspension feeders
• Most tube feet used for locomotion
• Tube feet around mouth modified as branched
  tentacles that pick up food from substrate or
  filter particles from water
• Earthworms of the sea
• Deposit feeders have long, coiled intestines
  (why?)
• Evisceration as defense mechanism
• Can eject toxic filaments or viscera (internal
  organs) through anus to deter predators

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Enypniastes eximia
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• Echinodermata
• Crinoidea (Feather stars, Sea lilies)
• Suspension feeders
• Mouth oriented upward
• Capture particles with tube feet/mucus
• Ciliated ambulacral grooves transport food to
  mouth
• Cling to substrate with cirri
• Capable of swimming Video Clip
• Feather stars Unstalked
• Cosmopolitan, but especially abundant in warm
  water
• Capable of swimming
• Sea lilies Stalked
• Uncommon, restricted to deep water

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• Lophophorates
• Three phyla all animals possess lophophore
• Ciliated hollow tentacles arranged in a horseshoe
• Suspension feeders
• Bilateral symmetry, coelom (body cavity),
  U-shaped gut
• Bryozoa/Ectoprocta Bryozoans
• Colonies consist of interconnected individual
  zooids
• Encrusting and lacy forms (CaCO3 tests)
• Retractable lophophore
• Phoronida Phoronids, Horseshoe Worms
• Worm-shaped
• Agglutinated sediment tubes attached to hard
  substrate in shallow water
• Brachiopoda Lamp Shells
• Abundant in fossil record
• Superficially resemble clams, but shells are
  dorsal-ventral, not left-right as in mollusks
• Many attached to substrate with pedicle (short
  stalk)

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Bryozoa
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• Lophophorates
• Three phyla all animals possess lophophore
• Ciliated hollow tentacles arranged in a horseshoe
• Suspension feeders
• Bilateral symmetry, coelom (body cavity),
  U-shaped gut
• Bryozoa/Ectoprocta Bryozoans
• Colonies consist of interconnected individual
  zooids
• Encrusting and lacy forms (CaCO3 tests)
• Retractable lophophore
• Phoronida Phoronids, Horseshoe Worms
• Worm-shaped
• Agglutinated sediment tubes attached to hard
  substrate in shallow water
• Brachiopoda Lamp Shells
• Abundant in fossil record
• Superficially resemble clams, but shells are
  dorsal-ventral, not left-right as in mollusks
• Many attached to substrate with pedicle (short
  stalk)

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• Lophophorates
• Three phyla all animals possess lophophore
• Ciliated hollow tentacles arranged in a horseshoe
• Suspension feeders
• Bilateral symmetry, coelom (body cavity),
  U-shaped gut
• Bryozoa/Ectoprocta Bryozoans
• Colonies consist of interconnected individual
  zooids
• Encrusting and lacy forms (CaCO3 tests)
• Retractable lophophore
• Phoronida Phoronids, Horseshoe Worms
• Worm-shaped
• Agglutinated sediment tubes attached to hard
  substrate in shallow water
• Brachiopoda Lamp Shells
• Abundant in fossil record
• Superficially resemble clams, but shells are
  dorsal-ventral, not left-right as in mollusks
• Many attached to substrate with pedicle (short
  stalk)

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• Chaetognatha (Arrow Worms)
• Important components of the plankton
• Voracious carnivores
• Sit and wait predators
• Eat zooplankton (small crustaceans, larvae, eggs)

Fig 7.41
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• Enteropneusta (Acorn Worms)
• Hemichordates
• Possible evolutionary transition between
  invertebrates and chordates
• Share some but not all characteristics with
  chordates
• Deposit feeders
• Many construct U-shaped burrows and process large
  quantities of sediment
• Proboscis secretes mucus used to collect organic
  material

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• Chordata
• Characteristics
• Dorsal hollow nerve cord
• Pharyngeal gill slits
• Notochord
• Postanal tail
• Three subphyla
• Urochordata Tunicates
• Cephalochordata Lancelets
• Vertebrata Vertebrates

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• Chordata
• Urochordata - Tunicates
• Ascidiacea (Class) Sea squirts
• Only sessile chordates
• Solitary (single or clumped)
• Colonial
• Body covered by tunic (gelatinous outer covering)
• Active suspension feeders (filter feeders)
• Water pumped in through incurrent siphon and out
  through excurrent siphon
• Particles filtered out by feeding basket
  (pharynx)
• Planktonic tadpole larva
• Possesses all four chordate characteristics
• Doesnt feed resorbs notochord and tail at
  settlement

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Fig 7.48