I. SYNONYMS: Trichomonads, Hypermastigids, Polymonads.

II. NUMBER: >2,000 species known.

III. PHYLUM CHARACTERISTICS:

• A. Structure and Physiology
  • Cell Form: Unicellular.
  • Flagella: Several or many flagella borne on the anterior end of the cell; in clusters of 4 or multiples of 4 (?) with 3 anterior (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 one posterior ( recurrent (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. ) flagellum.
  • Basal Bodies: At least some of the basal bodies (text with tooltip) Basal bodies (also called kinetosomes) are organelles that are not membrane-bound. All eukaryotic flagella (also called undulipodia) are underlain or attached to the cell by the basal body. The basal body is a microtubular structure with the general formula 9(3)+0. They are indistinguishable from centrioles. are associated with parabasal (text with tooltip) Parabasal bodies are large modified golgi bodies that lie in association with the basal bodies and flagellar roots of the Parabasalotista. structures composed of striated filamentous fibers with closely allied golgi complexes. Cytoplasmic microtubular elements also arise from the basal bodies. Basal bodies appear to be parallel (text with tooltip) Basal bodies are parallel when their orientation relative to each other is parallel. .
  • Cell Covering: Naked; with specialized cytostome (text with tooltip) Cytostome (literally cell mouth) is a permanent opening into the cell into which food particles move and are incorporated into food vacuoles. -like region on posterior end of cell.
  • Chloroplasts: Not present.
  • Food Reserves: Not reported.
  • Mitochondria: Not present, but hydrogenosomes (text with tooltip) Hydrogenosomes are symbiotic bacteria or organelles that generate hydrogen as a kind of anaerobic mitochondrion. , anaerobic metabolic organelles, in some.
  • 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 and modified to parabasal body, a golgi complex that is attached by a striated root (text with tooltip) Striated roots (also called kinetodesma, banded roots, kinetodesmal fibers, or striated fibers) are banded flagellar roots that elaborate from basal bodies. They form a distinctive and diagnostic network in the Ciliata. , the parabasal root, to the nucleus.
  • Nucleus: In karyomastigonts (text with tooltip) A karyomastigont is a 'unit' that includes basal bodies, flagellar roots, and a nucleus. ; or the axostyle (text with tooltip) An axostyle is rod-like microtubular structure that occurs in certain Metamonadotista and Parabasalotista. The axostyle runs through the axis of the cell from the anterior (usually anchored around the nucleus) to the posterior end, often forming an extended point at the posterior end. associated with nucleus (sometimes encapsulating it). Chromosomes remain condensed during interphase.
  • Centrioles: Not reported but certain basal bodies with elaborate “atractophores” (text with tooltip) An atractophore is a rod-like structure that elaborates from the basal body and behaves as a centriole. behave as centrioles.
  • Inclusions and Ejectile Organelles:
  • Food vacuoles:

• B. Mitosis, Meiosis and Life History
  • Mitosis: The nuclear membrane remains intact ( 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). ) during mitosis; the spindle is extranuclear (text with tooltip) An extranuclear spindle elaborates outside of the bounds of the nuclear envelope (the nuclear envelope does not break down). and extends across one side of the nucleus with chromosomes connected to microtubules at kinetochores (text with tooltip) A kinetochore is also called a centromere, the point on a chromosome to which the spindle fibers attach. situated in the nuclear envelope; the spindle poles are associated with “atractophores” (fibrous extensions from certain basal bodies).
  • Meiosis: Presumed.
  • Sexual Reproduction and Life History:
  • Reported in some.

C. Ecology: Mostly endobiotic (text with tooltip) Endobiotic (adj.) means 'living within'. This refers to endosymbionts. and phagotrophic (text with tooltip) Phagotrophic (adj.) refers to a cell (or organism) that engulfs food particles. . A few taxa are free-living.