Mychonastes P.D.Simpson & S.D.Van Valkenburg, 1978

Holotype species: Mychonastes ruminatus P.D.Simpson & S.D.Van Valkenburg

Original publication and holotype designation: Simpson, P.D. & Van Valkenburg, S.D. (1978). The ultrastructure of Mychonastes ruminatus gen. et sp. nov., a new member of the Chlorophyceae isolated from brackish water.. British Phycological Journal 13(2): 117-130.

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Description: Cells solitary or in groups rarely more than 4. Cells spherical or slightly ovate, 1-10 µm or up to 30 µm diameter. Cell walls with irregular arrangement of ridges only visible with electron microscopy; one species with 1-2 dark brown spots of iron encrustation. Cells uninucleate; chloroplast single and parietal, up to 4 prior to spore production; pyrenoids absent. Asexual reproduction by autospores, 2 or 4 or up to 64 formed per cell; released by rupture of parental cell walls; residues of cell walls remaining in cultures. Flagellated stages and sexual reproduction unknown. Mychonastes planktonic with M. ruminatus in brackish water; known only from Chesapeake Bay, Maryland; found throughout the year but a dominant during August, September. In culture growth at 1- 30 0/00 with cell size decreasing with increasing salinity; growth decreasing below 10 0/00 and above 20 0/00. Other species reported from Europe, occurring in freshwater (M. homosphaera) or isolated from soil (M. zofingiensis). 18S rRNA analysis of chlorococcalean algae by Wilcox and others (1992) suggest that M. homosphaera (as C. minutissima) closer to Nanochlorum, than Chlorella. Taxonomic position complicated by absence of cultured strain of type species. Further study required to define monophyletic nature of genus and its affinities. Genus distinguished from Chlorella based on cell wall features and absence of pyrenoid, although pyrenoid present or absent in Chlorella depending on generic concepts. Genus variously assigned to Oocystaceae or subfamily Scotiellocystoideae of Tetraedronaceae (or Chlorellaceae). Species distinguished based on cell size, number of autospores, chloroplast morphology and habitat. Chemotaxonomy of pigments supports recognition of genus. Cells solitary or in groups rarely more than 4. Cells spherical or slightly ovate, 1-10 µm or up to 30 µm diameter. Cell walls with irregular arrangement of ridges only visible with electron microscopy; one species with 1-2 dark brown spots of iron encrustation. Cells uninucleate; chloroplast single and parietal, up to 4 prior to spore production; pyrenoids absent. Asexual reproduction by autospores, 2 or 4 or up to 64 formed per cell; released by rupture of parental cell walls; residues of cell walls remaining in cultures. Flagellated stages and sexual reproduction unknown. Mychonastes planktonic with M. ruminatus in brackish water; known only from Chesapeake Bay, Maryland; found throughout the year but a dominant during August, September. In culture growth at 1- 30 0/00 with cell size decreasing with increasing salinity; growth decreasing below 10 0/00 and above 20 0/00. Other species reported from Europe, occurring in freshwater (M. homosphaera) or isolated from soil (M. zofingiensis). 18S rRNA analysis of chlorococcalean algae by Wilcox and others (1992) suggest that M. homosphaera (as C. minutissima) closer to Nanochlorum, than Chlorella. Taxonomic position complicated by absence of cultured strain of type species. Further study required to define monophyletic nature of genus and its affinities. Genus distinguished from Chlorella based on cell wall features and absence of pyrenoid, although pyrenoid present or absent in Chlorella depending on generic concepts. Genus variously assigned to Oocystaceae or subfamily Scotiellocystoideae of Tetraedronaceae (or Chlorellaceae). Species distinguished based on cell size, number of autospores, chloroplast morphology and habitat. Chemotaxonomy of pigments supports recognition of genus. Emended by Krienitz, C. Bock, Dadheech & Proschild (2011: 99).

Information contributed by: T. Kalina & D. Garbary. The most recent alteration to this page was made on 2014-03-25 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Tsarenko, P.M. (2011). Chlorococcales. In: Algae of Ukraine: diversity, nomenclature, taxonomy, ecology and geography. Volume 3: Chlorophyta. (Tsarenko, P.M., Wasser, S.P. & Nevo, E. Eds), pp. 232-264. Ruggell: A.R.A. Gantner Verlag K.-G..

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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.

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Citing AlgaeBase
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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 25 March 2014. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 24 April 2024

 
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