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Invertebrate Zoology

Lecture Notes 

Platyhelminthes - Gnathostomulida

 

Notes:  This is an outline of my class notes - details and visuals will be given in class!

Read: Chapter 14 in Hickman, Roberts & Larson.

  1. Phylum Platyhelminthes
    1. Gr. platys - flat + helmins, - worm
    2. Pla tee hell min' thees
    3. Figures 14-2 to 14-22 pp. 283-296
    4. There are 25,000 species
    5. Bilateral symmetry
    6. Body flattened dorso-ventrally
    7. Three embryonic germ layers: endoderm, mesoderm, ectoderm
    8. Organ level of organization
    9. Extracellular digestion in gastrovascular cavity, intracellular in gastrodermal cells
    10. Excretory system (protonephridia)
    11. Simple respiration by diffusion
    12. Anterior ganglia and two longitudinal nerve cords (nerve ladder)
    13. Sense organs, some with eyespots
    14. Non-parasitic forms may crawl or swim by muscular/ciliary movements
    15. No skeletal system
    16. Reproduction usually sexual
      1. Sexual forms usually monecious
      2. Asexual reproduction by fission
    17. Mostly marine, some freshwater, many parasitic
    18. Origins unknown
    19. Classes
      1. Turbellaria
        1. Figures 14-2(283), 14-3 - 14-5(284), 14-6(285), 14-7, 14-8(286), 14-9, 14-10 (287), 14-11 (288).
        2. L. turbellae - bustle - + aria - like
        3. Tur'bel-lar' e-a
        4. Mostly free-living
        5. From 5mm to 50 cm
        6. rhabdites produce mucus
        7. usually carnivorous
        8. protonephridia with flame cells
        9. can regenerate
        10. about 4,500 species
      2. Trematoda (flukes)
        1. 14-12(289), 14-13, 14-14(291), 14-15 (292)
        2. Gr. trematodes, with holes + eidos, form
        3. Trem' a-to'da
        4. similar to turbellaria, but no cilia
        5. hooks or suckers for attachment, most internal organs retained
        6. indirect life cycle
          7.
          1. intermediate host mollusc
            1. asexual reproduction takes place here
          2. final host vertebrate
            1. sexual reproduction takes place here
        7. 9,000 species (with Monogenea)
      3. Monogenea
        1. 14-16(293)
        2. Gr. mono, single + gene, origin
        3. Mon' o-gen' e-a
        4. monogenetic flukes
        5. parasitize fish gills, frog & turtle bladders, hippopotamus eyes
      4. Cestoda (tapeworms)
        1. 14-17, 14-18(293), 14-19(295), 14-20 to 14-22(296)
        2. Gr. kestos, girdle, eidos, form
        3. Ses-to' da
        4. serial reproductive organs (proglottids)
        5. scolex for attachment
        6. usually no reproduction in intermediate hosts
          1. massive production of eggs instead
        7. about 5,000 species

     

  2. Nemertea - Ribbon worms
    1. Nemertea - a figure from Greek mythology; a daughter of Nereis, Nemertes, the unerring one
    2. Nem-er'te-ans
    3. 14-23, 14-24(297), 14-25 to 14-27(298)
    4. bilateral symmetry
    5. to 60 meters long, usually under 20 cm
    6. most marine, some freshwater, terrestrial
    7. free-living, predaceous
    8. through gut
    9. blood-vascular system
    10. pilidium larvae
    11. eversible proboscis
    12. mostly dioecious, can reproduce by fragmentation
    13. flame cells for excretion
    14. simple respiration
    15. over 900 species

     

  3. Gnathostomulida
    1. Gr. Gnathos, jaw + stoma, mouth
    2. Nath' o-sto-myu' lid-a
    3. 14-28(300)
    4. bilateral symmetry
    5. to 1mm
    6. marine meiofauna
    7. free-living, detritivores
    8. incomplete gut
    9. direct development
    10. scraping pharynx
    11. monecious
    12. simple excretion
    13. simple respiration
    14. 80 species

 

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09/19/00

 

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