Pseudocoelomates

Pseudocoelomates - 5/31/10 "PROTOSTOMES" (see...

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5/31/10 1 “SMALL LOPHOTROCHOZOANS & SMALL ECDYSOZOANS” 5 th edition: chapter 9 and pp. 222-230 of chapter 12 4 th edition: chapter 9 and pp. 263-266 of chapter 13 “PROTOSTOMES” “LOPHOTROCHOZOA” “ECDYSOZOA” -acoelomates (last week & today) -pseudocoleomate, & coelomate phyla (today) “Gnathiferans”: Phyla Gnathostomulida Micrognathozoa (monotypic) *Rotifera *Acanthocephala *Phylum Gastrotricha *Phylum Cycliophora (1995) *Phylum Entoprocta *Lophophorate phyla: Ectoprocta, Brachiopoda, Phoronida 5 th ed.: Chapter 9 some of the “smaller phyla” today trochophore larva (most) possess a lophophore (some) (see inside of text cover) PROTOSTOMES LOPHOTROCHOZOA ECDYSOZOA acoelomate (last week & today) pseudocoleomate, & coelomate phyla (today) some of the “smaller phyla” today Pseudocoelomate Phyla: *Nematoda *Nematomorpha Kinorhyncha Priapulida Acoel/Pseudo: Loricifera external cuticle is molted as organism grows 5 th ed.: p222-230 4 th ed.: p263-266 text inside cover: 10 lophotrochozoan phyla 5 th ed.: Chapter 9 an evolutionary “ grade ”: - a group that shares the same level of organization &/or similar features, but not necessarily a common ancestor et al… the pseudocoelomate “grade” Ectoprocts
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5/31/10 2 Recall… flatworms (acoelomate) most of today’s phyla (pseudocoelomate) Pseudocoelomate - cavity derived from blastocoel (not from within mesoderm), so not enclosed entirely by mesoderm & hence, not a true coelom. In pseudocoelomate taxa, the original blastocoel of the embryo persists as a space or cavity between the gut and the body wall. Fig. 9.1 (4 th: 9.2) The pseudocoelom may be filled with fluid or gelatinous material with mesenchyme cells. It generally provides greater freedom of movement. There is now space for more development of digestive, excretory, and reproductive systems (vs. acoelomates). It is simpler to distribute materials throughout the body. This provides a storage area for waste products to be later discharged. Fluid-filled cavity provides hydrostatic support & the cavity is a base for mesodermal muscles that provide movement.
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5/31/10 3 Lab manual : lists 7 distinct phyla as belonging to the pseudocoelomate grade ( Rotifera, Acanthocephala, Gastrotricha, Nematoda, Nematomorpha, Kinoryncha and Ectoprocta ) - some new phyla discovered since manual was written - some taxonomic revision/controversy Chapter 9: ten lophotrochozoan phyla Fig. 9.2 * * * * * * * * -some are acoelomate -some are pseudocoelomate -some are coelomate (new edition) Features shared by most (or all) of these lophotrochozoan phyla: protostomes with triploblastic organization ; usually small size complete gut (only Acanthocephala lack gut): mouth, anus most with a pseudocoelom - closed fluid-filled sac with multiple functions: (1) hydrostatic “skeleton” ; (2) circulation (no blood- vascular system); (3) contains organs for reproduction & excretion ( most phyla have protonephridial excretory system)
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This note was uploaded on 06/29/2010 for the course BSC2011L BSC2011L taught by Professor Spears during the Summer '10 term at FSU.

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Pseudocoelomates - 5/31/10 "PROTOSTOMES" (see...

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