Glaucophyta

Content
Summaries of the Ten Algal Divisions
  Cyanophyta and Prochlorophyta
  Glaucophyta
  Rhodophyta
  Heterokontophyta
  Haptophyta
  Cryptophyta
  Dinophyta
  Euglenophyta
  Chlorarachniophyta
  Chlorophyta
Endosymbiosis and Origin of Eukaryotic Algae

Glaucophytes (Figure 1.28) are basically unicellular flagellates with a dorsiventral construction; they bear two unequal flagella, which are inserted in a shallow depression just below the apex of the cell. Glaucophytes are rare freshwater inhabitants, sometimes collected also from soil samples. They posses only chlorophyll a and accessory pigments such as phycoerythrocyanin, phycocyanin, and allophycocyanin are organized in phycobilisomes. Carotenoids such as β-carotene and xanthophylls such as zeaxanthin are also present in their chloroplast. This unusual chloroplast lies in a special vacuole and presents a thin peptidoglycan wall located between the two plastid outer membranes. Thylakoids are not stacked. The chloroplast DNA is concentrated in the center of the chloroplast, where typically carboxysomes are present, which contain the RuBisCo enzyme. Starch is the reserve polysaccharide, which is accumulated in granular form inside the cytoplasm, but outside the chloroplast. Glaucophytes live photoautotrophically with the aid of blue-green plastids often referred to as cyanelles. Cyanelles are presumed to be phylogenetically derived from endosymbiotic cyanobacterium. Sexual reproduction is unknown in this division.
 
A group of eight autospore of Glaucocystis nostochinearum still retained within parent cell
FIGURE 1.28 A group of eight autospore of Glaucocystis nostochinearum still retained within parent cell
wall. (Bar: 10 µm.)