Phacotus Perty, 1852

Holotype species: Phacotus viridis Perty

Currently accepted name for the type species: Phacotus lenticularis (Ehrenberg) Diesing

Original publication and holotype designation: Perty, M. (1852). Zur Kenntniss kleinster Lebensformen: nach Bau, Funktionen, Systematik, mit Specialverzeichniss der in der Schweiz beobachteten. pp. 1-228, 17 plates. Bern: Verlag von Jent & Reinert.

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Description: Unicellular,biflagellate and uninucleate algae with protoplasts contained in a firm,strongly compressed, colorless to brownish lorica; color resulting from iron deposition.In narrow side view, lorica obviously consists of two equal sections withclosely adpressed contact margins, sometimes slightly raised forming anindistinct keel. Lorica surface smooth, slightly roughened or variouslyornamented. In broad front view, lorica ovoid, ellipsoid, globose orbroadly and irregularly undulate. Protoplast somewhat smaller thanlorica. Chloroplast parietal, cup-shaped, with an anterior stigma, withor without a pyrenoid. Flagella anterior, emerging from a common openingin lorica or from separate openings. Two contractile vacuoles present atbase of flagella.Asexualreproduction by division into 2- 4-8(-16) daughter cells. Daughter cellsreleased on separation of two halves of mother cell lorica. Sexual reproductionapparently occurs by fusion of isogametes, giving rise to quadriflagellateplanozygote; mature zygote with thickened wall. Meiosis presumably zygotic.

Information contributed by: G.E. Dillard. The most recent alteration to this page was made on 2012-06-29 by Michael Guiry.

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

Most recent taxonomic treatment adopted: Masjuk, N.P., Lilitska, G.G. & Kapustin, D.O. (2011). Chlamydomonadales. In: Algae of Ukraine: diversity, nomenclature, taxonomy, ecology and geography. Volume 3: Chlorophyta. (Tsarenko, P.M., Wasser, S.P. & Nevo, E. Eds), pp. 157-218. Ruggell: A.R.A. Gantner Verlag K.-G..

Comments: Phacotus cosmopolitan with twelve well described species; allinfrequently encountered freshwater forms, in many cases known only fromtype localities. Four additional species of doubtful taxonomic validitywere described by Playfair (1918, P. bullatus) and Skvortzow (1957, P.asiaticus, P. hyalina, P. oblongus). P. bullatusmay not be properly assigned to Phacotus (Ettl 1983a; Huber-Pestalozzi1961), whereas the Skvortzow taxa are poorly described.InPhacotus lenticularis (Ehrenberg)Stein, the normally copious mucilageenvelope is greatly reduced in thickness in cells grown in nitrogen-supplementedmedium. Depending upon nitrogen source, the structure and composition ofthe lorica varies. Ultrastructurally, visualization of lorica andmucilage is enhanced by staining with alcian blue, thus corroborating chemicalevidence of a high anionic charge density. By weight, the lorica was 36 %carbohydrate (glucose the principal sugar); 26 % protein; 4 % sulfate; andvarious minerals, mainly calcium and manganese, comprising the remainder.The extracellular mucilage is a glycoprotein, with hydroxyproline as principal amino acid. Loricas subjected to protease and trypsin digestion undergostructural alteration

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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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Michael Guiry in Guiry, M.D. & Guiry, G.M. 29 June 2012. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 25 February 2024

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