I. SYNONYMS: chytrids

II. NUMBER: > 900 species.

III. PHYLUM CHARACTERISTICS:

• A. Structure and Physiology
  • Cell Form: Unicellular to filamentous; usually with a concentration of ribosomes next to the nucleus; a prominent oil droplet and a rumposome (text with tooltip) Structure composed of interconnecting tubules at the posterior end of the zoospore. body.
  • Flagella: Zoospores and sperm with a single posteriorly-directed (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. whiplash (text with tooltip) (1) A whiplash flagellum is a eukaryotic 9+2 flagellum with few or no flagellar hairs or scales. These may be directed anteriorly or posteriorly. (2) A whiplash flagellum is free of hair-like mastigonemes and usually is trailing or posteriorly-directed. flagellum; some are multiflagellated.
  • Basal Bodies: Two; parallel (text with tooltip) Basal bodies are parallel when their orientation relative to each other is parallel. with barren basal body (text with tooltip) Basal body with no associated flagellum. alongside active basal body (rumposome) in some or detached and not parallel in others; with microtubular roots; Catenaria zoospores (text with tooltip) A zoospore is an asexual spore that is motile. Zoo- (pronoumced zo-o) is a prefix that means moving. with microtubular basket attached to the nucleus.
  • Cell Covering: Secreted body wall of chitin and glucan.
  • Chloroplasts: Not present.
  • Food reserves: Oil.
  • Mitochondria: Flattened cristae (text with tooltip) Flat cristae (crista, sing.) are wall-like cristae within certain mitochondria. .
  • 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: Cells uninucleate.
  • Centrioles (text with tooltip) Centric (adj) describes a type of diatom that is radially symmetrical. It also describes nuclear division in which centrioles are present. : Present.
  • Inclusions and Ejectile Organelles: Not present.

• B. Mitosis, Meiosis and Life History
  • Meiosis: Zygotic in the Chytridiomycetes and in the diploid phase of Blastocladeomycetes.
  • Sexual Reproduction and Life History: Isogamous (text with tooltip) Isogamous (adj) describes sexual reproduction in which the gametes are structurally identical. to anisogamous (text with tooltip) Anisogamous (adj.) describes sexual reproduction in which the gametes are structurally siimilar, but not identical. , at least 1 gamete is motile; zygotes may germinate to form a resting spore.
    • Life Cycle of Polyphagus

• C. Ecology: Parasitic or saprobic.