The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of freshwater unicellular algae, less common today than they were during the Proterozoic.Evolutionary Biology: A Plant Perspective Only 15 species have been described, but more species are likely to exist.The monoplastidic bottleneck in algae and plant evolution | Journal of Cell Science Together with the red algae (Rhodophyta)  and the green algae plus land plants (Viridiplantae or Chloroplastida), they form the Archaeplastida.
However, the relationships among the red algae, green algae and glaucophytes are unclear, in large part due to limited study of the glaucophytes.
The glaucophytes are of interest to biologists studying the development of chloroplasts because some studies suggest they may be similar to the original algal type that led to green plants and red algae in that they may be basal Archaeplastida.
Unlike red and green algae, glaucophytes only have asexual reproduction.Plants: A Very Short Introduction Characteristics
The plastids of glaucophytes are known as 'muroplasts', 'cyanoplasts', or 'cyanelles'.
Unlike the plastids in other organisms, they have a peptidoglycan layer, believed to be a relic of the endosymbiotic origin of plastids from cyanobacteria.
Glaucophytes contain the photosynthetic pigment chlorophyll a.
Along with red algae and cyanobacteria, they harvest light via phycobilisomes, structures consisting largely of phycobiliproteins.
The green algae and land plants have lost that pigment.Skuja, A. (1948).
Taxonomie des Phytoplanktons einiger Seen in Uppland, Schweden.
Symbolae Botanicae Upsalienses 9(3): 1-399.
Like red algae, and in contrast to green algae and plants, glaucophytes store fixed carbon in the cytosol.
Glaucophytes have mitochondria with flat cristae, and undergo open mitosis without centrioles.
Motile forms have two unequal flagella, which may have fine hairs and are anchored by a multilayered system of microtubules, both of which are similar to forms found in some green algae.
Classification
Phylogeny of Glaucocystophyceae.
Only 13 species of glaucophytes are known, none of which is particularly common in nature.
The five included genera are:
Phylum Glaucophyta Skuja 1948
Class Glaucocystophyceae Schaffner 1922 [Cyanophorophyceae]
Order Cyanophorales Kies & Kramer 1986
Family Cyanophoraceae Kies & Kramer 1986
Genus ?Peliaina Pascher 1929
Peliaina cyanea Pascher 1929
Genus ?Strobilomonas Schiller 1954
Strobilomonas cyaneus Schiller 1954
Genus Cyanophora Korshikov 1924 (is motile and lacks a cell wall)
C. tetracyanea Korshikov 1941
C. biloba Kugrens et al. 1999
C. sudae Takahashi & Nozaki 2014
C. paradoxa Korshikov 1924
C. kugrensii Takahashi & Nozaki 2014
C. cuspidata Takahashi & Nozaki 2014
Order Gloeochaetales Kies & Kremer 1986
Family Gloeochaetaceae Bohlin 1901 ex Skuja 1954
Genus Cyanoptyche Pascher 1929 (is the least studied of the seven genera)
Cyanoptyche gloeocystis Pascher 1929
Genus Gloeochaete von Lagerheim 1883 [Schrammia Dangeard 1889 non Britton & Rose 1930 non Guppy 1895; Cyanochaete Gobi 1916] (has both motile and immotile stages, and its cell wall does not appear to be composed of cellulose)
G. wittrockiana von Lagerheim 1883
Order Glaucocystales Bessey 1907
Family Glaucocystidaceae Bohlin 1901 ex West 1904
Genus Glaucocystopsis Bourrelly 1961
Glaucocystopsis africana Bourrelly 1961
Genus Glaucocystis Itzigsohn 1868 (is immotile, though it retains very short vestigial flagella, and has a cellulose wall)
G. bullosa (Kützing 1836) Wille 1919
G. caucasica Tarnogradskii 1957
G. cingulata Bohlin 1897
G. duplex Prescott 1944
G. molochinearum Geitler
G. simplex Tarnogradskii 1959
G. nostochinearum Itzigsohn 1868 ex Rabenh.
1935
G. geitleri Pringsheim 1958 ex Takahashi & Nozaki 2016
G. incrassata (Lemmermann 1908) Takahashi & Nozaki 2016
G. miyajii Takahashi & Nozaki 2016
G. bhattacharyae Takahashi & Nozaki 2016
G. oocystiformis Prescott 1944
The glaucophytes were considered before as part of family Oocystaceae, in the order Chlorococcales.
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