Placoma
| Generic name: PLACOMA Schousboe ex Bornet et Thuret, 1876. Notes Algol. 1: 4. | ||||||||||
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| Type species: Placoma vesiculosum Schousboe 1876 | ||||||||||
| Descriptions: Komárek & Anagnostidis (1998): Cells in more or less globular colonies, located near the surface of gelatinous, irregular spheres; thallus is small or expanded, mucilaginous, more or less lobate or vesiculose with wavy or smooth surface, usually «hollow», with cells situated in one or several layers in the outer part of the colony, irregularly or radially arranged in irregular rows or groups, or in flattened layers. Gelatinous envelopes colourless, yellow-brownish or pinkish coloured. Cells without or with individual envelopes, which are sometimes layered, more or less spherical, irregular in outline or slightly elongate, with homogeneous, blue-green, olive-green, yellow-green or pinkish, sometimes slightly granular content. Komárek (1992):Unicellular - colonial; thallus small or expanded, gelatinous, more or less spherical, irregular spherical, slightly lobate or vesiculose with waved surface, usually hollow, with cells situated in one or several layers on the surface of a colony, irregularly, radially or in irregular rows or groups. Gelatinous envelopes colourless, yellow-brownish or pinkish coloured. Cells with or without special own envelopes, sometimes layered, more or less spherical, irregular in outline or slightly elongated, with homogeneous, blue-green, olive-green, yellow-green or pinkish, sometimes slightly granular content. Geitler (1932): Lager halbkugelig oder unregelmäßig-gekröseartig, gefaltet, lappig, im Alter im Innern hohl, weit ausgebreitete Überzüge bildend. Zellen in weiten blasigen Hüllen, nach Art von Gloeocapsa in Zellfamilien, welche an der Peripherie des Lagers mehr oder weniger deutlich radial orientiert sind. |
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| Genotype differences, molecular data: | ||||||||||
| Reproduction strategies, life cycles, cell division: Komárek & Anagnostidis (1998): Cell division irregular, in various planes, predominantly perpendicular to the surface of a colony. Reproduction by solitary liberated cells or by mucilaginous clusters of cells. Freshwater (usually from running waters) as well as marine species (rocky littorals of seas and oceans); only one species known from Europe. Komárek (1992): Cell division irregular, probably in more planes, predominantly perpendicular to the surface of a colony. Reproduction probably by solitary liberated cells or by mucilaginous clusters of cells. |
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| Ultrastructure: | ||||||||||
| Taxonomic position, higher hierarchy: Cyanophyceae, Chroococcales, Hydrococcaceae Notes to taxonomy, misinterpretations: |
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| Ecology, ecophysiology, ecological significance: Komárek (1992): Three species known from rocky littorals of seas and oceans; freshwater species described from wet rocks with streaming water or from streams of different kind from very distant localities allover the world. Little known genus, which needs further studies. |
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| Distribution, endemism, problematic citations: |
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| List of species: Placoma africanum Wille 1903 Placoma regulare Broady et Ingerfeld 1991 Placoma vesiculosum Schousboe in Bornet et Thuret 1876 Placoma violaceum Setchel et Gardner in Gardner 1918 Placoma willei Gardner 1927 Unclear taxa: |
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Drawings: Komárek 1992
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