SYNOPTIC DESCRIPTION OF THE PHYLUM OOMYCOTA (WINTER 1879)
| EUKARYA> CHROMALVEOLATA> HETEROKONTAE> OOMYCOTA |
OOMYCOTA LINKS
| The following description comes from Margulis and Schwartz (1988 and 1998), Dick (1990), Fuller (1990), Barr and Desaulniers (1989), and Beakes (1989). |
I. SYNONYMS: Oomycetes, water molds, phycomycota.
II. NUMBER: >800 species.
III. PHYLUM CHARACTERISTICS:
- A. Structure and Physiology
- Cell Form: Unicellular to siphonaceous (text with tooltip) Siphonous (adj) describes a filament that has no cross walls. filaments (with or without crosswalls).
- Flagella: Zoospores (text with tooltip) A zoospore is an asexual spore that is motile. Zoo- (pronoumced zo-o) is a prefix that means moving. with one anteriorly-directed (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. tinsel (text with tooltip) A tinsel flagellum is one that is covered with flagellar hairs and thus appears thicker in light microscopy. Usually, tinsel flagella are anteriorally-directed. flagellum or with two flagella, one anteriorly-directed tinsel flagellum and a 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. 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.
- Basal bodies: The two 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. lie at 180o in the oomycetes; single functional basal body attached to “centriole” in hyphochytridiomycetes.
- Cell covering: Cell covering of cellulose and/or chitin.
- Chloroplasts: Not present.
- 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: Diploid.
- Centrioles: Present and outside nucleus.
- 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). or open with polar fenestrae.
- Meiosis: Gametic (text with tooltip) Gametic meiosis occurs when gametes are the immediate results of meiosis. .
- Sexual reproduction and life history: Isogamous (text with tooltip) Isogamous (adj) describes sexual reproduction in which the gametes are structurally identical. to oogamous. Life histories of Saprolegnia and Phytophthora are representative of the phylum.
- C. Ecology: Parasitic or saprobic in water or soil.
| LITERATURE CITED Barr, D. J. S. and N. L. Desaulniers. 1989. The flagellar apparatus of the Oomycetes and Hyphochytridiomycetes. In: Green, J. C., B. S. C. Leadbeater, and W. L. Diver, eds. The chromophyte algae; problems and perspectives. Systematics Association Special Volume No. 38. Clarendon Press. Oxford. pp. 343-355. Beakes, G. W. 1989. Oomycete Fungi: their phylogeny and relationship to chromophyte algae. In: Green, J. C., B. S. C. Leadbeater, and W. L. Diver, eds. The chromophyte algae: problems and perspectives. Systematics Association Special Volume No. 38. Clarendon Press. Oxford . pp. 325-342. Bold, H. C., C. J. Alexopoulos, and T. Delevoryas. 1987. Morphology of Plants and Fungi. 5th edition. HarperCollins Publishers. New York. Dick, M. W. 1990. Oomycota. In: Margulis, L., J.O. Corliss, M. Melkonian, and D.J. Chapman, eds. 1990. Handbook of the Protoctista; the Structure, Cultivation, Habits and Life Histories of the Eukaryotic Microorganisms and Their Descendants Exclusive of Animals, Plants and Fungi. Jones and Bartlett Publishers. Boston . pp. 661-685. Fuller, M.S. 1990. Hyphochytridiomycota. In: Margulis, L., J. O. Corliss, M. Melkonian, and D. J. Chapman, eds. 1990. Handbook of the Protoctista; the structure, cultivation, habits and life histories of the eukaryotic microorganisms and their descendants exclusive of animals, plants and fungi. Jones and Bartlett Publishers. Boston. pp. 380-387. Margulis, L. and K. Schwartz. 1988. Five kingdoms, an illustrated guide to the phyla of life on earth. 2nd Edition. W.H. Freeman and Co. New York. Margulis, L. and K. Schwartz. 1998. Five kingdoms, an illustrated guide to the phyla of life on earth. 3rd Edition. W. H. Freeman and Company. New York. Patterson, D. J. 1999. The diversity of eukaryotes. American Naturalist. 154 (Suppl.): S96–S124. Sogin, M. L. and D. J. Patterson. 1995. Stramenopiles. Version 01 January 1995 (under construction). http://tolweb.org/Stramenopiles/2380/1995.01.01 In: The Tree of Life Web Project, http://tolweb.org/ |
| By Jack R. Holt. Last revised: 02/26/2012 |
