The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of unicellular
algae found in freshwater and moist terrestrial environments,[1][2] less common today than they were during the
Proterozoic.[3] The stated number of species in the group varies from about 14 to 26.[4][5][6] Together with the
red algae (Rhodophyta) and the
green algae plus land plants (
Viridiplantae or Chloroplastida), they form the
Archaeplastida.
The glaucophytes are of interest to biologists studying the evolution of
chloroplasts as they may be similar to the original algal type that led to the red algae and green plants, i.e. glaucophytes may be
basal Archaeplastida.[1][7][4]
The most early-diverging genus is Cyanophora, which only has one or two plastids. When there are two, they are semi-connected.[13]
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.[11]
Phylogeny
External
Together with
red algae and
Viridiplantae (
green algae and
land plants), glaucophytes form the
Archaeplastida – a group of
plastid-containing organisms that may share a unique common ancestor that established an
endosymbiotic association with a
cyanobacterium. The relationship among the three groups remains uncertain, although it is most likely that glaucophytes diverged first:[4]
The alternative, that glaucophytes and red algae form a clade, has been shown to be less plausible, but cannot be ruled out.[4]
Internal
The internal phylogeny of the glaucophytes and the number of genera and species varies considerably among taxonomic sources. A phylogeny of the Glaucophyta published in 2017 divided the group into three families, and includes five genera:[14]
Glaucophyta
Cyanophoraceae
Cyanophora
Gloeochaetaceae
Cyanoptyche
Gloeochaete
Glaucocystidaceae
Glaucocystopsis
Glaucocystis
Taxonomy
A 2019 list of the described glaucophyte species has the same three subdivisions, treated as orders, but includes a further five unplaced possible species, producing a total of between 14 and 19 possible species.[4]
As of March 2022[update],
AlgaeBase divided glaucophytes into only two groups, placing Cyanophora in Glaucocystales rather than Cyanophorales (however the entry was dated 2011).[15] AlgaeBase included a total of 26 species in nine genera:[16]
^Cruzan, Mitchell B. (2018). Evolutionary Biology. Oxford University Press. p. 20.
ISBN978-0-19-088268-6.
^
abcdeFigueroa-Martinez, Francisco; Jackson, Christopher; Reyes-Prieto, Adrian (2019). "Plastid Genomes from Diverse Glaucophyte Genera Reveal a Largely Conserved Gene Content and Limited Architectural Diversity". Genome Biology and Evolution. 11 (1): 174–188.
doi:
10.1093/gbe/evy268.
PMC6330054.
PMID30534986.
^
abSkuja, A. (1948). Taxonomie des Phytoplanktons einiger Seen in Uppland, Schweden. Symbolae Botanicae Upsalienses 9(3): 1-399.Guiry, M.D.; Guiry, G.M.
"Glaucophyta". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.