Oedogonium Link ex Hirn, 1900
Lectotype species: Oedogonium grande Kützing ex Hirn
Original publication: Hirn, K.E. (1900). Monographie und iconographie der Oedogoniaceen. Acta Societatis Scientiarum Fennicae 27: i-iv, 1-394, 27 figures, 44 plates.
Request PDFType designated in: Tiffany, L.H. (1937). Oedogoniales Oedogoniaceae. North American Flora 11(1): 1-102, incl. 36 pls.
Description: Unbranched uniseriate filaments attached to substratum by basal holdfast cells; occasionally free-floating. Vegetative cells generally uniform in size and shape in each species; usually cylindrical, but sometimes undulate, nodulate, or even angulate in profile view; all cells in filament normally capable of division. Shapes of basal holdfast cell and apical cell often distinctive. Vegetative cells uninucleate, highly vacuolate, and with a large reticulate, parietal chloroplast containing one to many (usually) pyrenoids. Pyrenoid matrix penetrated by numerous, branched, cytoplasmic channels. Asexual reproduction by means of zoospores, although fragmentation of filaments and germination of aplanospores and akinetes may also occur. Zoospores produced singly in zoosporangia developed directly from vegetative cells. Each zoospore with small hyaline anterior region at the base of which is borne a ring of many flagella (ca. 150). Upon emergence from zoosporangium each zoospore initially enveloped by delicate, transparent vesicle. Following liberation from vesicle and short period of motility, zoospore attaches to substratum, loses flagella and begins dividing to form new filament. Sexual reproduction oogamous; monoecious or dioecious. Species either macrandrous (lacking dwarf males) or nannandrous (with dwarf males). Dwarf males are small, short, antheridium-producing filaments attached near oogonia and derived from multiflagellate androspores through repeated cell division. Single division of oogonial mother cell forms swollen oogonium subtended by a supporting (suffultory) cell. Oogonia single or in a series; each with single large egg. Short, disk-shaped antheridia contain 1-2 multiflagellate sperm cells. Motile male gametes exit antheridia and are chemotactically attracted to oogonia. Fertilization follows passage of sperm cell through pore or slit-like opening in oogonial cell wall. Zygotes (oospores) initially green, but gradually become red or orange-red and develop a thick, often multilayered, cell wall with species specific surface ornamentation. Meiosis in zygote prior to germination leads to formation of four multiflagellate cells. Following short motility period, each of these cells attaches to a substratum and divides repeatedly to form new filament.
Information contributed by: L.R. Hoffman & M.D. Guiry. The most recent alteration to this page was made on 2019-01-30 by M.D. Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
Most recent taxonomic treatment adopted: Huxley, R. & Pentecost, A. (2002). Order Oedogoniales. In: The Freshwater Algal Flora of the British Isles. An identification guide to freshwater and terrestrial algae. (John, D.M., Whitton, B.A. & Brook, A.J. Eds), pp. 409-432. Cambridge: Cambridge University Press.
Comments: Oedogonium species are typically epiphytic and attached to aquatic vegetation or inorganic substratum by a basal holdfast cell; sometimes free-floating. Most commonly encountered in shallow standing waters, e. g., ponds, lakes and ditches. Common in freshwater habitats worldwide; only a few species in brackish water. Greatest abundance of species in temperate and subtropical regions. Cell division distinctive of Oedogoniales. Involves formation of ring of new cell wall material near apical end of dividing cell prior to mitosis. Following mitosis, the parental cell wall splits into two unequal portions that remain in contact with this ring. The two portions of the parental cell wall gradually separate as wall material constituting ring "stretches" to form new cylindrical cell wall components shared by the two developing daughter cells following cytokinesis. The apical-most daughter cell receives a large portion of new wall material from ring, and only a small cap-like portion of old parental cell wall. As a result, this cell bears the distinctive marking of an "apical cap" at it apex. A series of apical caps (up to >20) may occur on a cell that has undergone repeated cell division. A phycoplast forms during cytokinesis. Species differ markedly in cell size with diameters ranging from 4-54 µm, commonly 14-30 µm. Chromosome size and number likewise variable according to species; length from <1 µm to >20 µm and n=9 to ca. 41. The validity of some species may be questioned, particularly in view of recognition of polyploidy in the genus and the polymorphic nature of many taxonomic characters.
Oedogonium with its simple unbranched filament has been postulated to be the most primitive genus in the order, although data to support this opinion is inadequate. Experimental studies have examined the role of hormonal substances in sperm attraction and in regulation of sexual reproduction in nannandrous species. Ultrastructural studies have investigated developmental aspects of cell division, zoosporogenesis, and gametogenesis.
Verification of Data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.
Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera,
organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA)
and intended to be published in CD format.
These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above.
The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.
Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.
Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=43424
Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 30 January 2019. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 22 November 2024
