BI338 Invertebrate Zoology, Fall 2011 Brian K. Penney, Ph.D. Goulet 2320, Ph 641-7149, email: bpenney (at) anselm.edu

Main Page Definitions Phyla Other Links Review Section Projects

Lophophorates

• a grouping of three phyla, uncertain if truly related.
• Important evolutionarily because they possess a mix of protostome and deuterostome traits.
• all share lophophore (ciliated, horseshoe-shaped organ for suspension feeding)

1. List features shared among lophophorate phyla, briefly discussing features that may not be unique shared features
   • Horseshoe-shaped feeding crown of ciliated tentacles, that surrounds mouth but not anus (lophophore); grows from mesocoel [U]
   • U-shaped gut
   • Prosome reduced to small, flaplike epistome, or lost
   • Simple, often transient reproductive systems from peritoneum
   • often asexual reproduction
   • Nearly all secrete outer casings (shells, tubes, exoskeletons)
   • Nearly all marine (except some freshwater bryozoans)

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2. List and briefly discuss the features that indicate an intermediate position for lophophorates between Protostomes and Deuterostomes

   [replaces the normal question of "list and discuss general animal characters seen in phylum, so this will not be asked individually of lophophorate phyla]

   • deuterostome: i) tripartite body plan (prosome, mesosome, metasome), each with separate, paired coelomic compartments developmentally, ii) radial cleavage
   • protostome: i) blastopore = mouth in Phoronida, ii) protonephridia in some larval forms, iii) chemistry of exoskeleton (chitin based); iv) 18S rDNA
   • intermediate: rRNA
   • implies either lophophore is not unique feature, or that these supposedly "deep" characters can be labile within one group!

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3. Name and describe features of Bryozoa

   (= Ectoprocta; ca. 4,000 ppp.). Marine and freshwater colonial suspension feeders.

   • Develop from single sexually produced individual (ancestrula); zooids within colony often polymorphic. (e.g. autozoids vs avicularia, vibracula)
   • Individuals generally connected by funiculus
   • Typical circulatory and excretory structures absent; epistome generally absent; some excretion via brown bodies?
   • Zooids (=polypides) in gelatinous, chitinous or calcareous covering (cystid/zooecium); extension via hydrostat of metac/mesooel
   • Lophophore U-shaped or circular

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4. Diagram and label a saggital section through a typical bryozoan
   • B2 Fig 21.10J

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5. Name and describe features of Phoronida
   • small phylum of small, marine, benthic or infaunal worms.
   • one pair metanephridia in metasome
   • changed axis (extension of larval ventral side)
   • Closed circulatory system with hemoglobin and blood cells
   • blastopore=mouth!

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6. Diagram and label a saggital section through a typical phoronid

   B2 Fig 21.2E (note split section)

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7. Name and describe features of Brachiopopda

   (ca. 300 spp.) Marine bivalved filter feeders.

   • Body enclosed by two shells, usually unequal (dorsal = branchial/ventral = pedicle) and attached to substratum by pedicle.
   • Lophophore extended, coiled, sometimes with internal support
   • Rudimentary, open circulatory system
   • No asexual reproduction
   • Two classes: Articulata (hinge, no anus, pedicle simple) and Inarticulata (no hinge, anus, pedicle with muscles and all body layers)

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8. Diagram and label a saggital section through a typical brachiopod

   -B2 Fig 21.19A

   • note ventral and dorsal sides!

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9. Describe how lophophorates approach the basic functions of animals, indicating where appropriate differences among these phyla
   
   1. Movement in Lophophorates ()
   2. Support in Lophophorates ()
   3. Feeding in Lophophorates (Carolyn)
      • The lophophore surrounds the mouth and is an upstream collecting system for suspension feeding.
      • Food particles are brought through the tentacles and trapped in a mucus lining.
      • The gut is U-shaped with the anterior mouth at the center of the lophophore.
      • The anus, where present, is also anterior, but is dorsal to the mouth.
      • Food is moved through the U shaped gut by cilia.
      • Major digestion occurs intercellular in the stomach.
   4. Reproduction in Lophophorates ()
   5. Circulation in Lophophorates (Molly)
      • They contain an extensive circulatory system comprising two major longitudinal vessels between which blood is exchanged in the lophophoral and stomachic ends of the body. The capillary ceca brings blood close to the gut wall and other organs. Blood flows through vessels through hemal spaces. Blood is moved through the circulatory system largely by muscular action of the blood vessel walls.
      • Nutrients are picked up from the stomach by the circulatory fluid and transported throughout the body. The tentacles are also the most important site of gas exchange.

      [IS THIS TRUE OF ALL THREE PHYLA?]

   6. Gas exchange in Lophophorates ()
   7. Excretion/water balance in Lophophorates ()
   8. Growth and development in Lophophorates ()
   9. Sensation and coordination in Lophophorates (Molly)
      • Nervous system is diffuse and lacks a distinct cerebral ganglion. Most is associated with the body wall. Simple sensory neurons arise from the epidermis, singly or in bundles, and extend the body surface as the only receptor structures.

      [BRYOZOA HAVE GANGLION? COORDINATON AMONG ZOOIDS?]

   10. Defense against predators and pathogens in Lophophorates (BKP)
       • HARD CASINGS FOR ALL PHYLA
       • CHEMICAL DEFENSE KNOWN FOR BRYOZOA

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updated: 12/7/11

all writing and graphics, copyright Brian K. Penney and the 2008- 2010 years' classes, unless otherwise noted