Ochromonas Vysotskii, 1887
Lectotype species: Ochromonas triangulata Vysotskii
Original publication: Vysotskii, A.V. (1887). Mastigophora i Rhizopoda, naydennyya v Veysovom i Repnom ozorakh. Otchet ob ekskursii dlya izsledovaniya slavyanskikh solyanykh ozer Khar'kovskoy gubernii, v botanicheskom otnoshenii [Mastigophora and Rhizopoda, found in Veysovoe and Turnip lakes. Report on the excursion for the study of the Slavic salt lakes of the Kharkov province, in botanical terms]. pp. ii, 20, 2 plates. Kharkiv: Universitetskoy Tipografiya. [in Russian]
Type designated in: Lemmermann, E. (1899). Das Phytoplankton sächsischer Teiche. Forschungsberichte aus der Biologischen Station zu Plön 7: 96-135, pls I, II.
Description: Cells naked, solitary, spherical-to-ellipsoid or pyriform in face view and not compressed intransverse section. Front end obliquely truncate, has an emargination from which 2 microscopically visible unequal flagella emerge, one long bearing tripartite tubular hairs, the other short and smooth. Cells usually free-swimming, occasionally resting or attaching to substrate at the posterior end. Cells may become amoeboid, losing the flagella. Cell surfaces of several species covered with small wart-like outgrowths. Chloroplasts 1-2, rarely several, yellow-to-brown or rarely greenish, usually with a stigma and in a few species a pyrenoid. Sometimes chloroplasts are much reduced and pale, and by abnormal divisions cells may lose their chloroplasts. Chloroplasts contain a girdle lamella with chloroplast DNA arranged in a ringshaped structure just inside. They are enclosed by the chloroplast endoplasmatic reticulum which may be continuous with the nuclear envelope. Protoplast contains 1-4 contractile vacuoles, one or several chrysolaminaran vesicles, food vacuoles, and sometimes numerous trichocyst-like bodies (mucocysts, discobolocysts) under the cell surface. Asexual reproduction involves either division of activemotile cells or immobile cells dividing within gelatinous envelopes. Cells dividing in gelatinous envelopes may produce palmelloid colonies with many cells. During mitosis the spindle microtubules make direct connections with rhizoplasts, which are fibrous structures extending from the flagellar basal bodies. The nuclear envelope largely disappears during mitosis, only small portions connected to the chloroplast persisting. Sexual reproduction unknown. Many species produce stomatocysts. The formation process has been described in detail for O.tuberculata Hibberd. The silica of the stomatocyst wall is laid down within a silica deposition vesicle, whose membrane (the silicalemma) is very much like that of diatoms. Most studies on cytology, biochemistry, physiology, and nutrition haveused O.danica Pringsheim (Aaronson 1974, Cole and Wynne 1974, Loeblich and Loeblich 1978). Auxotrophy for various vitamins is common. Heterotrophic nutrition, both by osmotrophic and phagotrophic means, accompanies the photosynthetic mode. Solid food is engulfed into a primary food vacuole, which migrates to the posterior portion of the cell and is incorpotated into a larger digestion vacuole. Excretion products of O.danica include a variety of mebranous vesicles, carbohydrates, nucleic acid-like molecules, proteins (including enzymes), lipids, and vitamins. Reports on O.malhamensis, another species often used in experimental studies, should be referred to Poteriochromonas malhamensis. Species of Ochromonas occur worldwide, some probably cosmopolitan. Most species are freshwater plankton forms, others are also brackish and marine. Note: In the present treatment of genera of Chrysophyceae the order/family Ochromonadales/Ochromonadaceae (cells with two unequal flagella) has been included in the Chromulinales/Chromulinaceae (cells with one flagellum visible in the light microscope), since electron microscopy has demonstrated the two flagella on various "uniflagellates" (see Preisig 1995), and since species of both Ochromonas and Chromulina are otherwise very similar, except for the length of the short flagellum. It has to be shown in the future (e.g. by gene sequencing), whether such a combination of higher-level-taxa is really justified, or whether separate orders and families should be recognized.
Information contributed by: H.R.Preisig. The most recent alteration to this page was made on 2022-10-26 by E.A. Molinari Novoa.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
Gender: This genus name is currently treated as feminine.
Most recent taxonomic treatment adopted: Kawai, H. & Nakayama, T. (2015). Introduction (Heterokontobionta p.p.), Cryptophyta, Dinophyta, Haptophyta, Heterokontophyta (except Coscinodiscophyceae, Mediophyceae, Fragilariophyceae, Bacillariophyceae, Phaeophyceae, Eustigmatophyceae), Chlorarachniophyta, Euglenophyta. In: Syllabus of plant families. Adolf Engler's Syllabus der Pflanzenfamilien. Ed. 13. Phototrophic eukaryotic Algae. Glaucocystophyta, Cryptophyta, Dinophyta/Dinozoa, Haptophyta, Heterokontophyta/Ochrophyta, Chlorarachnniophyta/Cercozoa, Chlorophyta, Streptophyta p.p. (Frey, W. Eds), pp. 11-64, 103-139. Stuttgart: Borntraeger Science Publishers.
Comments: Kristiansen & Preisig (2001: 9) record this genus as alternately being a member of the family Ochromonadaceae Lemmerman 1899. Nicholls & Wujek (2003) record this genus as being a member of the Order Ochromonales. Throndsen (1997: 618) record this genus as being a member of the Family Ochromonadaceae, Order Ochromonadales and Class Chrysophyceae.
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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.
Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=43790
Cite this record as:
E.A. Molinari Novoa in Guiry, M.D. & Guiry, G.M. 26 October 2022. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 11 December 2023