Glaucophyta (glau-KA-fa-ta) is formed from two Greek roots that mean blue-green (glauko -γλαυκο); and plant (phyto -φυτό).  The reference is to the blue-green color of the cyanelles.  Glaukos also was a Greek sea god.


All glaucophytes occur in freshwater, but are rarely observed.  They tend to be coccoid and occur in loose colonies formed by the persistent cell wall of the parent cell following division (Figure A).  When they form motile cells (Figure B), the flagella are heterodynamic and covered with mastigonemes.  The base of the flagellar apparatus is associated with a multilayered structure (MLS) and cruciate flagellar roots, characters also associated with the Praesinophyta (in the Viriviplantae).  

They are clearly blue-green and their plastids retain aspects of the primary cyanobacterial endosymbiont not seen in any other taxa (except an unrelated euglyphid amoeba or Cyanomonas).  Because the endosymbionts retain a thin murein wall and appear to be cyanobacterial, the plastids are usually called cyanelles (Figure C).  They have subsurface sacs, a character that Patterson (1999) listed as an identifying synapomorphy.  If these sacs are alveoli, they might destroy the defining synapomorphy of the Alveolatae. 


Moreira et al. (2000) and recent supertree analyses (Baldauf 2003; Keeling 2004; and Nikolaev et al. 2004) confirm the monophyly of the three groups.  Cavalier-Smith (2002, 2003) interprets the Rhodophytes and Viridiplantae as sister groups while the Glaucophytes are outgroups within the Plant clade.  Other analyses (Bhattacharya et al. 1995 and Nikolaev et al. 2004) showed them to be very different from the viridiplantae+rhodophytae.  Patterson (1999) includes the glaucophytes in his list of sisterless taxa, but includes Cyanidium in that group.

In the past they have been classified with the cryptophytes (Bourrelly 1970; Moestrup 1982), the chlorophytes (Bourrelly 1966), rhodophytes (Schnepf and Brown 1971; Cavalier-Smith 1982, 1986; Melkonian 1984), and the chlorophytes+euglenophytes (Moestrup 1982; Melkonian 1982, 1983; Kies and Kremer 1990).  Since 1990, the group has been classified independently (e.g. Kies and Kremer 1990; Patterson 1999; Graham and Wilcox 2000; Van den Hoek et al. 1995, and Lee 1999).  Clearly, these taxa hold uncertain status within the plants, the primary photosymbionts.

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A. Glaucocystis, a coccoid taxon.

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B. A motile cell of Cyanophora.  Note the heterodynamic flagella. 

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C. A TEM micrograph of Glaucosphaera that shows the cyanobacterial nature of the cyanelles.

Images taken from:


The description of this phylum comes from Bold and Wynne (1985), Van den Hoek et al. (1995), Graham and Wilcox (2000), Kies and Kremer (1990), and Patterson (1999).

I. SYNONYMS: glaucophytes.

II. NUMBER: >13 species (9? genera).


A. Structure and Physiology

Cell Form: Unicellular and loose colonies.

Flagella: 2 unequal flagella present in most with mastingonemes, inserted subapically; 9+0 pseudocilia in some.

Basal Bodies: Present; with a multi-layered structure (MLS) and cruciate flagellar roots.

Cell Covering: Covered by a thick proteinaceous cell wall.

Chloroplasts: Numerous coccoid cyanelles, dominated by blue-green phycobillins; with chlorophyll a, B-carotene, xanthophylls. 

Food Reserves: True starch free in the cytoplasm.

Mitochondria: Plate-like cristae.

Golgi: Present and associated with the basal bodies and/or the nucleus.

Nucleus: Uninucleate.

Centrioles: Not present.

Inclusions and Ejectile Organelles: Pulsating vacuole.

B. Mitosis, Meiosis and Life History

Mitosis: Open; division by infurrowing.

Meiosis: Not known.

Sexual Reproduction and Life History: Not known.

C. Ecology: Mainly found in fresh water habitats; rare.


This is a modification of Kies and Kremer (1990) and Lee (1999).



Glaucocystis, Cyanophora, Gloeochaete, Glaucosphaera.


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Melkonian, M. 1984. Flagellar apparatus ultrastructure in relation to green algal classification. In: Irvine, D. E. G. and D. M. John, eds. Systematics of the Green Algae. Academic Press. London/Orlando. pp. 73-120.

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Van Den Hoek, C., D. G. Mann, and H. M. Jahns. 1995. Algae, An Introduction to Phycology. Cambridge University Press.  Cambridge.

By Jack R. Holt.  Last revised: 03/21/2010