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Microcrocis

Generic name: MICROCROCIS Richter, 1892. In Hauck et richter, Phyk. Univers., Fasc. 11: 548.
Synonyms: BECKIA Elenkin, 1933. Monogr. Alg. Cyanoph. URSS, pars. Spec. 1: 71.; HOLOPEDIUM (Lagerheim) Lagerheim, 1893. Nuova Notarisia 4: 209.; PSEUDOHOLOPEDIA (Ryppowa) Elenkin, 1935. Monogr. Alg. Cyanoph. URSS 1: 539.; [Druet & Daily, 1956; Richter in Hauck & Richter, Phyk. Univ. 11: 548. 1892. Holopedium Lagerheim. Nuova Notarisia 4: 209. 1893. Merismopoedia Subgenus Holopedium Lagerheim, Ofvers. K. Sv. Vet.-Akad. Forh. 40(2): 43. 1883. Holopedium - Subgenus Microcrocis Fotti, Syll. Myxophyc., p. 111. 1907. -Type species: Merismopoedia geminata Lagerh.]
Diagnosis:
Type species: Microcrocis dietelii Richter 1892.
Descriptions:
Komárek & Anagnostidis (1998): Colonies microscopic to macroscopically visible, flat, tabular, free-living, mucilaginous,
composed of one layer of densely packed cells, sometimes composed of subcolonies; cells sometimes arranged in perpendicular rows (usually in young colonies), later quite irregularly (in several species rows of cells rarely are formed); mucilage colourless, cells without individual mucilaginous envelopes. Cells elongate, ellipsoidal, oval or rod-shaped, with rounded ends, oriented with their longer axis perpendicular to the plane of colony (during the life cycle stages with rounded cells occur). Thylakoids (in M. geminata) are wavy and disposed through the whole cell content (Chang in litt.).

Komárek (1992):Unicellular - colonial; colonies many-celled, microscopic, rarely macroscopically remarkable (with many cells), table-like, flat or slightly waved, uniserial, mucilaginous, usually with irregular outline, with cells gathered in one layer in the plane of colony; in young colonies are the cells more or less in rows perpendicular one to another, in old colonies irregularly and usually very densely gathered, in several cases up to polygonal in outline (subg. Beckia). Mucilaginous envelope fine, colourless, diffluent; cells without their own mucilaginous envelopes. Cells rarely spherical when young, later (at least in a part of the life cycle)
elongated, situated perpendicularly to the plane of colony, widely oval, oval up to rod-like, with rounded ends, sometimes several hundreds in a colony; cells usually without visible chromatoplasma (irregular arrangement of thylakoids within the cells).

Geitler (1932, sub Holopedia): Zellen zu tafelförmigen Kolonien von mehr oder weniger unregelmäßigem Umriß vereinigt, ellipsoidisch bis zylindrisch (die Längsachse senkrecht auf der Fläche der Kolonie stehend), mit abgerundeten Enden, ohne Spezialhüllen, in
gemeinsamer Gallerte liegend. Teilungen nach zwei Raumrichtungen, parallel zur Längsachse.

Genotype differences, molecular data:
Reproduction strategies, life cycles, cell division:
Komárek & Anagnostidis (1998): Cells divide lengthwise in two perpendicular planes in successive generations (i. e., lengthwise with the longer cell axis) and perpendicularly to the plane of colony; cells separate and slightly shift apart from one another after division. Reproduction by disintegration of colonies. During the vegetation cycle of several species there are various morphological («Synechocystis-», «Merismopedia-», typical «Microcrocis-») stages.
Komárek (1992): Division of cells more or less in two planes, perpendicularly one to another and to the plane of colony (i.e., lengthwise); the cells form in young colonies the perpendicular rows, later in more-celled colonies are arranged irregularly. Reproduction by the disintegration of colonies.
Ultrastructure:
Taxonomic position, higher hierarchy:
Cyanophyceae, Chroococcales, Merismopediaceae, Merismopedioideae
Notes to taxonomy, misinterpretations:
Ecology, ecophysiology, ecological significance:
Komárek (1992): Epipelic and metaphytic species growing mainly in small water bodies (pools and waters with water vegetation or with sandy substrate), but two species are known from brackish up to salinic localities in flat sea beaches and in riverine aestuaries (M. sabulicola, M. marina). Known from northern temperate zone, rarely from tropics (mainly not revised data).
Physiology and biochemistry:
Distribution, endemism, problematic citations:
Reference strain:
Infrageneric scheme, species concept:
List of species:
Microcrocis bella (Beck-Mannagetta) Komárek et Anagnostidis 1995
Microcrocis dietelii Richter 1982
Microcrocis geminata (Lagerheim) Geitler 1942
Microcrocis gigas (Ryppowa) Komárek et Anagnostidis 1995
Microcrocis granulata (Skuja) Skuja in Starmach 1966
Microcrocis irregilaris (Lagerheim) Geitler 1942
Microcrocis marina (Lagerheim) Komárek et Anagnostidis 1995
Microcrocis obvoluta (Tiffany) Frank et Landman 1988
Microcrocis pulchella (Buell) Geitler 1942
Microcrocis sabulicola (Lagerheim) Geitler 1942
Microcrocis solea (Komarenko) Komárek et Anagnostidis 1995

Unclear taxa:
Holopedia dednensis Pevalek 1925
Holopedia mutisiana Guerrero 1946
Holopedia clementei Guerrero 1946

Keys:
List of stains:
Drawings:
Komárek 1992
Application technology:
Literature:
  2.1 taxonomy: Geitler 1942, Skuja 1948, Fott 1972, Niell & Anadon 1978, Komárek & Anagnostidis 1986, Frank & Landman 1988, Komárek 1992, Komárek & Anagnostidis 1998
  2.2 cytomorphology:
  2.3 16S rRNA sequencing:
  2.4 biology and life cycles:
  2.5 ecology: