BI338 Invertebrate Zoology, Fall 2009 Brian K. Penney, Ph.D. Goulet 2320, Ph 641-7149, email: bpenney (at) anselm.edu

Main Page Definitions Phyla 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)
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!
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
4. Diagram and label a saggital section through a typical bryozoan
   • B2 Fig 21.10J
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!
6. Diagram and label a saggital section through a typical phoronid

   B2 Fig 21.2E (note split section)

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

   -B2 Fig 21.19A

   • note ventral and dorsal sides!
9. Describe how lophophorates approach the basic functions of animals, indicating where appropriate differences among these phyla
   
   1. Movement in Lophophorates (Santo)

      Type of Movement: Sedentary (Ectoprocts) and Locomotor (Brachiopoda)

      System Architecture: Circular and Longitudinal muscles. Circular muscles are only capable of limited movement.

      Control of System: Hydrostatic qualities of the coelomic chambers (protocoel, mesocoel, and metacoel) allows for contraction.

   2. Support in Lophophorates (Chris)

      Architecture:

      • Exoskeleton
        • Branchiopods are enclosed by two shells (each having 3 layers)
      • Hydrostatic
        • Provided by the coelomic chambers and by the tube.

      Growth:

      • Generally, the outer cuticle layer is secreted by the epidermis
      • In Branchiopods, the outer layer of the shell (the periostracum) is secreted by the mantle edges and the inner shell layer is secreted by the general mantle surface

      Muscle Antagonism and Movement:

      • Mainly concerned with the protraction and retraction of the lophophore
      • Mechanisms vary among species
      • Usually use the hydraulic pressure provided by the coelomic spaces to protract the lophophore
      • Use retractor muscles to pull the lophophore back into the protective tube
   3. Feeding in Lophophorates (Eric)

      Food Capture / Ingestion.

      • Generalized: Double row hollow tentacles, ciliated outer growths of meosome, filled with coelomic extensions containing blood vessels, draws food to mouth slit
      • Suspension Feeders, particles trapped in mucous lining of food groove

      Mechanical Breakdown

      • I did not see ONE thing in the chapter about it

      Chemical Breakdown

      • Gland cells in esophagus will possibly release secretions? Unknown

      Absorption

      • U shaped gut, not coiled
      • Transitory syncytial buldges in stomach walls, intracellular digestion

      Defecation

      • Food is removed via metanephridia and the anus
   4. Reproduction in Lophophorates (Courtney)

      Gamete formation and reproductive organs- simple, often transient reproductive systems from peritoneum; dioecious and hermaphroditic

      Gamete release/ delivery, mating- gametes carried into outside by nephridia

      Fertilization- external

      Incubation, brooding- external brooding in some ectoprocts, brooding until larval stage in brachiopods

      Asexual reproduction- bryozoa asexual colonies develop from single sexually produced individual (ancestrula), no asexual reproduction in brachiopoda

   5. Circulation in Lophophorates (Joanna)

      Circulatory fluid and carrier molecules

      • Blood cells and hemoglobin
      • Gases and nutrients

      Structural mechanism to pump fluid

      • Heart
      • Muscle action of blood vessel walls

      Path of fluid movement

      • Blood flows through a complex network of vessels, before it leaves the vessels and flows over the organs. Despite this setup, they are still considered to have a closed circulatory system

      System Architecture

      • Closed in Phoronid
      • Open in Brachipod
      • No system in Ectoprocts
   6. Gas exchange in Lophophorates (Emily)

      Ectoprocts

      Fluid movement across surface-movement is across the walls of the protraced parts of the polypide

      Architecture of system- the tentacles provide surface area but there is no specific system.

      Local conditions- there are not respirtory pigments to aid in anoxic condtions.

      Branchiopoda

      Fluid movement across surface-Occurs across the general body surface especially the large surface areas of the tentacles and mantle

      Architecture of system-Because of the presence of hemerythrin and the general arangment of the animal the coelomic fluid is the medium or oxygen transport not the blood.

      Local conditions-nothing is mentioned regarding anoxic conditions

   7. Excretion/water balance in Lophophorates (Jen)

      -phoronid-

      -a pair of metanephridia lie in the trunk; each has two nephrostomes opening to the metacoel

      -in heach nephridium, the nephrostomes join a curved nephridioduct, leading to a nephridiopore adjacent to the anus

      -not much is known, but crystalline matter has been seen to exit the nephridiopores, representing precipitated nitrogenous waste products

      -ectoproct

      -metabolic wastes are accumulated and transported by phagocytic coelomocytes

      -elimination of wastes not entirely known, but occurs partly by brown bodies

      -appearance of brown bodies associated with degeneration of polypides which is followed by reformation of a new polypide

      -it is thought that metabolic wastes are precipitated and concentrated in the brown bodies and therefore are eliminated or rendered inert

      -brachiopod

      -have one or two pairs of metanephridia with nephrostomes opening to the metacoel

      -nephridioducts exit through pores into the mantle cavity

      -nephridia discharge phagocytic coelomocytes that have the accumulated metabolic wastes

   8. Growth and development in Lophophorates (Maria)
      • Cleavage of embryo and blastula formation — radial cleavage of embryo
      • Germ layer formation and gastrulation — tripartite body plan (prosome, mesosome, metasome)
      • Mosaic vs. regulative control — regulative embryo control ?
      • Coelom formation — 3 paired coelomic compartments (echizocoelous ?)
      • Indirect or mixed development
      • Blastopore becomes mouth in Phoronida but not in Brachiopoda or Bryzoa
      • Segmentation — unsegmented?
   9. Sensation and coordination in Lophophorates (Zaynab)
      • Rather diffuse, lacks distinct cerebral ganglion (condition related to the sedentary lifestyle and overall reduction in cephalization in these worms)
      • Most nervous system is intimately associated with the body wall.
      • CNS comprises a simple intraepidermal nerve ring, which lies at the base of the lophophore and is continuous with the subepidermal nerve layer.
      • The nerve ring supplies the tentacles with nerves as well as giving rise to motor nerves to some of the longitudinal muscles in the metasome.
      • Phoronids possess one or two longitudinal giant motor fibers in the trunk.
   10. Defense against predators and pathogens in Lophophorates (Kayla)

       Phylum Phoronid:

       Physical:

       -defensibly ciliated

       Chemical, behavioral, immune: not much is known

       Phylum Bryozoa

       Physical

       Exoskeleton can be chitinous or calcified

       Posses Avicularia are modified to be jaws to defend the colony. Vibracula have modified whip like structures to defend the colony.

       Can have spines and protuberances

       Chemical:

       Can have chemicals against predators

       Behavioral and immune: not much is known

       Phylum: Brachiopod:

       Physical:

       Shells

       Spines in some animals

       Chemical, Immune, Behavioral:

       Not much is known

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