I. SYNONYMS: Sarcodina, amoebae, rhizopods, Myxomycota, myxomycetes, acellular slime molds, plasmodial slime molds.

II. NUMBER: > 600 species.

III. PHYLUM CHARACTERISTICS:

• A. Structure and Physiology
  • Cell Form: Uninucleate amoebae to large plasmodial (text with tooltip) A plasmodium is a multinucleate cell formed by nuclear divisions without cytokinesis. amoebae.
  • Flagella: Haploid zoospores (text with tooltip) A zoospore is an asexual spore that is motile. Zoo- (pronoumced zo-o) is a prefix that means moving. with a one or a pair of unequal anteriorly (text with tooltip) An anteriorly-directed flagellum extends in the direction of the motion of the motile cell. The interpretation is that the flagellum functions by pulling the cell. and posteriorly (text with tooltip) Recurrent flagella bend to the posterior end of the cell. Typically, they are identified as recurrent when anteriorly-directed flagella are present. directed flagella (sparsely hairy or whiplash?)
  • Basal Bodies: Orthogonal (text with tooltip) Basal bodies are perpendicular (or orthogonal) when their orientation relative to each other is at a right angle. ; roots with an outer microtubular array and a microtubular cone attached to the nucleus.
  • Cell Covering: Feeding cells naked; sclerotia (text with tooltip) A sclerotium (sclerotia) is a portion of a Myxotist plasmodium that forms a hardened chitinous outer covering as protection against dessication or other environmental extremes. Thus, it is an asexual structure that, while multinucleate, behaves as a cyst. with a chitinous covering.
  • Chloroplasts: Not present, although the cells of slime molds tend to be heavily pigmented.
  • Food Reserves: Not known.
  • Mitochondria: Tubular cristae (text with tooltip) Mitochondrial cristae that form as extended saccate structures or tubes are called tubular cristae. .
  • Golgi (text with tooltip) Golgi apparatus (also called dictyosome) is an internal membrane system of stacked flattened sacs. They occur in nearly all eukaryotes and are involved in storing and secreting cellular products. : Present.
  • Nucleus: Uninucleate to multinucleate plasmodium.
  • Centrioles: Not known.
  • Inclusions and Ejectile Organelles: Not present.

• B. Mitosis, Meiosis and Life History
  • Mitosis: Closed (text with tooltip) Mitosis is closed when the segregation of daughter chromosomes occurs within the bounds of the nuclear membrane (the nuclear membrane does not break down). with an intranuclear spindle (text with tooltip) An intranuclear spindle elaborates within the nuclear membrane of an organism with closed mitosis. .
  • Meiosis: Within spores.
  • Sexual Reproduction and Life History: Sexual reproduction occurs by fusion of haploid uninucleate cells to form a zygote that develops into a diploid plasmodium. Specialized sporangia develop from the plasmodium and meiosis occurs in the spores (probably the abortion of 3 nuclei occurs because a single amoeba emerges from each spore). Sexual life history not known in most groups.

• C. Ecology: Heterotrophic; feeding on bacteria.