Glaucophyte

Unlike red and green algae, glaucophytes reproduce exclusively through asexual means. They undergo open mitosis without centrioles, a trait shared with other basal eukaryotes. Reproductive modes include binary fission, zoospore formation, and autosporulation. For example, Cyanophora paradoxa divides longitudinally, producing two daughter cells, each inheriting a single cyanelle. Species of Glaucocystis reproduce via non-motile autospores. To date, there is no evidence of sexual reproduction in glaucophytes. ==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. This peptidoglycan layer plays a functional role in plastid division and is considered molecular evidence of their cyanobacterial ancestry. Glaucophytes contain the photosynthetic pigment chlorophyll a. Like red algae, and in contrast to green algae and plants, glaucophytes store fixed carbon in the cytosol. This cytosolic carbon fixation, rather than fixation within plastids, is considered a retained ancestral trait. Glaucophyte phycobilisomes are composed primarily of phycocyanin and allophycocyanin, two key pigments also present in cyanobacteria. These pigments allow absorption of light at wavelengths that chlorophyll cannot, enhancing light harvesting in low-light aquatic environments. Studies of endosymbiotic gene transfer (EGT) suggest that several genes originally encoded in cyanobacterial ancestors have been relocated to the nuclear genome in glaucophytes, reflecting early stages of plastid-host genomic integration. The evolution of glycogen and starch metabolism in eukaryotes gives molecular clues to understand the establishment of plastid endosymbiosis. The most early-diverging genus is Cyanophora, which only has one or two plastids. When there are two, they are semi-connected. 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. == 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: }} 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. • Order Cyanophorales • Genus Cyanophora – 5–6 species A recent study by Takahashi et al. (2023) used both morphological and molecular data to distinguish five distinct species within the genus Cyanophora, confirming species boundaries and supporting the utility of combined phylogenetic analysis. • Order Glaucocystales • Genus Glaucocystis – 7–8 species • Order Gloeochaetales • Cyanoptyche – 1 species • Gloeochaete – 1 species • Other possible species • ?Archaeopsis monococca Skuja • ?Chalarodora azurea Pascher • ?Glaucocystopsis africana Bourrelly • ?Peliaina cyanea Pascher • ?Strobilomonas cyaneus Schiller , AlgaeBase divided glaucophytes into only two groups, placing Cyanophora in Glaucocystales rather than Cyanophorales (however the entry was dated 2011). AlgaeBase included a total of 26 species in nine genera: • Glaucocystales • Chalarodora Pascher – 1 species • Corynoplastis Yokoyama, J.L.Scott, G.C.Zuccarello, M.Kajikawa, Y.Hara & J.A.West – 1 species • Cyanophora Korshikov – 6 species • Glaucocystis Itzigsohn – 13 species • Glaucocystopsis Bourrelly – 1 species • Peliaina Pascher – 1 species • Strobilomonas Schiller – 1 species • Gloeochaetales • Cyanoptyche Pascher – 1 species • Gloeochaete Lagerheim – 1 species None of the species of Glaucophyta is particularly common in nature. ==References==