21 Lophophorates Nov 11

21 Lophophorates Nov 11 - Phylum Sipuncula ~ 300 spp Marine...

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1 Phylum Sipuncula ~ 300 spp Marine Sedentary – burrow Unsegmented True Coelom Bilateral symmetry peanut worms Introvert : Anterior end of body drawn into trunk mouth at end, with ciliated tentacles Mouth anterior - surrounded by tentacles (simple or branched) Body wall: cuticle epidermis connective tissue muscles peritoneum Ture Coelom – large lots of cells – some with hemerythrin (respiratory pigment) Some phagocytic - immune URNS - not in all Can be fixed or free Collect particulate material in coelom Eliminated through funned organs Tentacles – controlled by closed hydrostatic system Compensation Sac vessel into each tentacle some blood cells ! circulator system? Gut – ciliated long, coiled, U-shaped held in place by spindle muscle anus – base of introvert Funnel organs – mixonephridia, large, easily seen in dissection - usually 1 pair
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2 Nervous System – ventral nerve cord (single) - no ganglia, bilobed brain Reproduction System – Separate Sexes - paired gonads - gametogenesis completed in coelom => funnel organs, external fertilization Spiral Cleavage, protostomes Direct dev. or indirect => Trochophore (nonfeeding) 4 patterns of development Few – asexual Trochophore Nonfeeding Pelagosphaera Feeding Pelagosphaera Adult Adult Embryo Adult Adult 3 Lophophorate Phyla : Phoronida , Brachiopoda , Bryozoa Unified by several characters Phylogenetic position uncertain - recently put with molluscs and annelids Share characters with both Duterostomes All have a Lophophore (= structure that bears a tuft) Lophophore – horseshoe shaped tentacle crown ciliated, creates water currents For suspension, feeding gas exchange Poorly cephalized Simple Nervous System U-shaped Gut (some have a blind gut) Gonads - loose aggregations of germ cells ~ Radial Cleavage Sessile/Sedentary Secrete a chitinous or calcareous “house” Phylum Phoronida
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3 Phylum Phoronida ~ 20 species, only 2 Genera Bilateral Symmetry Vermiform Marine Live in secreted tubes Most < 5 cm, some 15 cm usually form dense aggregations -tend to be uniformly spaced can occur over large areas of sandy bottom Lophophore coiled on both sides 100 to > 500 tentacles Mouth in center of crown Anus on midline, but Outside of lophophore Rest of body = Trunk Complete Gut – U-shaped, Ciliated - ciliary mucus feeding anus outside of lophophore between funnel organs Coelom – subdivded lophophore - has own coelomic cavity
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This note was uploaded on 01/27/2010 for the course BIO 37282 taught by Professor Padilla during the Fall '10 term at SUNY Stony Brook.

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21 Lophophorates Nov 11 - Phylum Sipuncula ~ 300 spp Marine...

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