Biology 625
Fall semester lecture note outline

Updated: 24 September 1999

The text below simply represents a crude lecture outline of one of the topics covered in class. It is not meant to substitute for attending lectures or ignoring the textbook. Additional material, including line drawings, kodachromes, and more extensive information on life-cycles and basic biology, will be supplied in the lectures.

TOPIC 38. Miscellaneous taxa

Phylum: Haplosporidia

  1. you will not be tested over this taxon
  2. distantly related to the dinoflagellates, Apicomplexa, and ciliates; but forming a distinct taxon in itself
  3. spore forming organisms with anterior pore sometimes covered by an operculum
  4. no polar tubes or polar filaments present
  5. all species parasites of invertebrates
  6. amoebula in spore which is the infective stage
  7. life-cycle of Haplosporidium nelsoni (MSX disease) in oysters
    1. it is thought that spores are ingested
    2. uninucleate or binucleate amoebula exits
    3. either invades host cell or crosses gut and enters body cavity
    4. karyokinesis without cytokinesis, resulting in multinucleate plasmodium
    5. uninucleate sporoblasts develop within plasmodoium
    6. fragments and each sporoblast develops into individual spore
    7. in some species, the nucleus within the sporoblast divides and then recombines
    8. most species, spores liberated from oysters are not infective to uninfected oysters. Another host may be involved.
  8. pathology of H. nelsoni involves degeneration of infected tissues and death of oysters
  9. other genera and species
    1. Bertramia in worms and rotifers
    2. Coelosporidium in cockroaches
    3. Minchinia in oysters, chitins, etc
    4. Urosporidium in polchaetes

Class: Perkinsasidea

  1. you will not be tested over this taxon
  2. most closely related to dinoflagellates, and distantly related to apicomplexans and ciliates; with apical complex composed of incomplete conoid, polar ring, subpellicular microtubules, rhoptries, and micronemes
  3. dispersal stages consisting as flagellated zoospores; with curved apical ribbon of microtubules surrounded by sheath
  4. homoxenous and without sexual reproduction
  5. few species; i.e. Perkinsus marinus in oysters off east coast and in Caribbean
    1. biflagellate zoospores in environment (2-4 micrometers long); flagella with mastigonemes
    2. phagocytosed by oysters
    3. enter epithelium of intestine
    4. multiple fission or budding
    5. young aplanospores (spores) produced, which enlarge
      1. 5-10 micrometers in diameter (some up to 30 micrometers)
      2. central vacuole, usually eccentric, with refringent inclusion termed vacuoplast
      3. 1-3 "lomasomes" and a single nucleus within the cytoplasm
    6. a germinating spore (sporangia) may also be produced from the aplanospore, with discharge tube; cytoplasm undergoes binary fission in spore
    7. aplanospore produces prezoosporangia, which is a multinucleate plasmodium
    8. plasmodia released into environment
    9. cytokinesis to produce zoosporangia that give rise to flagellated zoospores

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