I. SYNONYMS: Microsporidians, myxosporidiomycota, cnidosporidians.

II. NUMBER: >1500 species

III. PHYLUM CHARACTERISTICS

• A Structure and Physiology
  • Cell Form: Unicellular spores enclosed by an imperforate wall within which one uninucleate or dinucleate sporoplasm (text with tooltip) Ameba-like portion of a microsporidian cyst that is infective to the next host. is associated with and extrusion apparatus composed of a polar cap and an eversible polar filament (text with tooltip) Cellular organelle coiled inside spore. When a spore encounters a new host cell, the filament uncoils and injects the infective sporoplasm through the filament. . Amoeboid sporoplasm emerges from the polar tube when the spore “hatches,” and this often develops into a syncytial plasmodium. For illustrated spore structure and life history see Glugea Spore Structure and Life History.
  • Flagella: No flagella.
  • Basal Bodies: Not known.
  • Cell Covering: Spore wall of 3 layers.
  • Chloroplasts: Not present.
  • Food Reserves: Not known.
  • Mitochondria: Not present.
  • Golgi: Present.
  • Nucleus: Diploid?
  • Centrioles: Reported.
  • Inclusions and Ejectile Organelles:
  • Ejects polar filament from spore which resembles the nematocyst of the coelenterates.

• B. Mitosis, Meiosis and Life History
  • Mitosis: Closed with an intranuclear spindle whose poles center on plaques (centrioles??).
  • Meiosis: Suspected.
  • Sexual Reproduction and Life History:
  • Intracellular parasites of many organisms. Characteristic spore with evertible thread.

• C. Ecology: Parasites of animals and protists.