--------------- Mon. April 6 (cont.) -------------

• 1) The lophophorates include phyla with traits of both deuterostomes [tricoelomate body, radial cleavage, blastopore yields anus (e.g., brachiopods), coeloms via enterocoely (some)] & protostomes [larval protonephridia (some), mouth from blastopore (e.g., bryozoans)]

  a) most are sessile with a reduced head & secrete a protective covering

  b) two unifying traits are: 1) a lophophore [circular or horse-shoe shaped crown of ciliated tentacles around the mouth extended by the mesocoel], & 2) a U-shaped gut (anus lies outside lophophore)

  c) bryozoans: encrusting colonial animals with a polyp-like zooids that extend out of a gelatinous, leathery or calcareous exoskeleton; particles are caputured by lateral cilia or tentacular flicking

  d) brachiopods: solitary animals enclosed by paired (dorsal & ventral) shells & bearing a stalk-like pedicle; the coiled lophophore maximizes feeding efficiency vs rate; most went extinct 225 MYA

  --------------- Wed. April 8 -------------

• 2) Hemichordates are a pivotal group for understanding chordate origins

  a) two classes differ greatly in form & may belong in separate phyla

  b) the Cl. Pterobranchia are tube-dwelling, colonial animals with a well developed lophophore; feeding resembles bryozoans; zooids exhibit a clear tri-partite body and move about in the tubes on a creeping oral sheild; gill slits are small (one pair) or absent

  c) the Cl. Enteropneusta (acorn worms) are sediment-dwelling animals that also exhibit a clear tri-partite body; an extensive branchial chamber with ciliated, U-shaped gill slits, is very similar to that in SubPh. Cephalochordata (sister group to vertebrates)

  d) most enteropneusts feed on particles in sediment; some may filter feed; which mode is primitive remains unclear

• 3) Echinoderms and hemichordates share two unusual traits:

  a) a protocoelic nephridium (=axial complex)

  b) a coelomopore (=hydropore) connecting the protocoel to the outside of the body

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