Transcript Oct 27 - University of San Diego

I.
Keystone Species
I.
Echinodermata
A.
Echinoidea (Sea urchins, Sand dollars)
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Approximately 1000 species
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Includes heart urchins, sea biscuits
Round, rigid test with movable spines and pedicellariae
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Spines and tube feet used for locomotion
Tube feet in shallow ambulacral grooves along outside of
test
Complete digestive system
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Mouth on bottom, anus on top
Herbivores
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Feed on seaweeds and seagrasses (especially drifting) plus
attached encrusting organisms
Mouth includes Aristotle’s lantern
I.
Echinodermata
B.
Holothuroidea (Sea cucumbers)
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Lack spines
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Five rows of tube feet run from mouth to anus
Endoskeleton reduced to small calcareous spicules in skin
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Complete digestive system
Respiration through respiratory trees
Deposit and suspension feeders
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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
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Can eject toxic filaments or viscera (internal organs) through
anus to deter predators
Enypniastes eximia
I.
Echinodermata
C.
Crinoidea (Feather stars, Sea lilies)
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Suspension feeders
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Mouth oriented upward
Capture particles with tube feet/mucus
Ciliated ambulacral grooves transport food to mouth
Cling to substrate with cirri
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Capable of swimming Video Clip
Feather stars – Unstalked
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Cosmopolitan, but especially abundant in warm water
Capable of swimming
Sea lilies – Stalked
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Uncommon, restricted to deep water
II.
Lophophorates
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A.
B.
C.
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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
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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)
Bryozoa
II.
Lophophorates
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A.
B.
C.
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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
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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)
II.
Lophophorates
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A.
B.
C.
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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)
III. Chaetognatha (Arrow Worms)
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Important components of the plankton
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Fig 7.41 •
Voracious carnivores
Sit and wait predators
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Eat zooplankton (small crustaceans, larvae,
eggs)
IV. Enteropneusta (Acorn Worms)
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Hemichordates
Possible evolutionary transition between
invertebrates and chordates
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Share some but not all characteristics with
chordates
Deposit feeders
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Many construct U-shaped burrows and process
large quantities of sediment
Proboscis secretes mucus used to collect
organic material
V.
Chordata
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Characteristics
1)
2)
3)
4)
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Dorsal hollow nerve cord
Pharyngeal gill slits
Notochord
Postanal tail
Three subphyla
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Urochordata – Tunicates
Cephalochordata – Lancelets
Vertebrata – Vertebrates
V.
Chordata
A.
Urochordata - Tunicates
1.
Ascidiacea (Class) – Sea squirts
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Only sessile chordates
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Solitary (single or clumped)
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Colonial
Body covered by tunic (gelatinous outer covering)
Active suspension feeders (filter feeders)
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Water pumped in through incurrent siphon and
out through excurrent siphon
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Particles filtered out by feeding basket (pharynx)
Planktonic tadpole larva
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Possesses all four chordate characteristics
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Doesn’t feed – resorbs notochord and tail at
settlement
Fig 7.48