colonies of 2–4–8 spherical cells in a mucilagenous envelope
diameter cells 6–21 µm
each cell with gelatinous setae, 100–500 µm long
colored blueish-green by sausage-shaped cyanelles
cyanelles are arranged parietally
spherical nucleus central
Gloeochaete wittrockiana
So far I have only found Gloeochaete wittrockiana in the Simmelried, where the alga occurs rarely but regularly. In the samples, the colonies, which usually consist of 4 cells, are easily recognizable by their blueish-green color. The coloration is caused by so-called cyanelles, which are regarded as endosymbionts (s. fig. 4 a). In the course of evolution, cyanobacteria were taken up and integrated by the algae as symbionts. If an original chloroplast of the algae was present, it has been completely regressed.
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Gloeochaete wittrockiana is classified as a tetrasporal alga because the cells can form very long gelatinous setae (s. fig. 1). In the literature their length is given as 100–250 µm, but I was also able to find colonies with bristles 500 µm long (s. fig. 1). However, they are very delicate and the thin ends can easily be overlooked.
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The nucleus is located in the center of the cell. It appears to lie in a separate vacuole, which is free of cyanelles and which is separated from the ectoplasm by a granular layer (s. fig. 4 b).
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Skuja (1956) described that Gloeochaete wittrockiana can form swarmer with two flagella and two contractile vacuoles (s. drawings above). I myself have not yet been able to observe such swarmers.
Fig. 1:Gloeochaete wittrockiana. L = appr. 500 µm (of colony with gelatinous setae). A colony of 4 cells with long, delicate setae (arrows). The setae have a length of about 500 µm. Obj. 20 X.
Fig. 2 a-b:Gloeochaete wittrockiana. D = 13–15 µm (of cells). Two focal planes of a colony of 4 cells. Obj. 60 X.
Fig. 3:Gloeochaete wittrockiana. D = 15–17 µm (of cells). A colony of 4 cells in a mucilagenous envelope. Obj. 100 X.
Fig. 4 a-b:Gloeochaete wittrockiana. D = 12–13 µm (of cells). Focal plane on the blueish-green cyanelles (CY, a) and the nuclei (Nu, b). The cyanelles have a length of 3.5 µm. Obj. 100 X.
Fig. 5:Gloeochaete wittrockiana. A cluster of cells, mixed up with different species of algae, cyanobacteria and purple bacteria. Obj. 60 X.