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Keystone Species

Keystone Species. 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

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Keystone Species

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  1. Keystone Species

  2. 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 Aristotle’s lantern

  3. 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

  4. Enypniastes eximia

  5. 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

  6. 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)

  7. Bryozoa

  8. 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)

  9. 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)

  10. Chaetognatha (Arrow Worms) • Important components of the plankton • Voracious carnivores • Sit and wait predators • Eat zooplankton (small crustaceans, larvae, eggs) Fig 7.41

  11. 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

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

  13. 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 • Doesn’t feed – resorbs notochord and tail at settlement

  14. Fig 7.48

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