Cosmarium boeckii Wille, 1880

Most likely ID: n.a.

 

Synonym: n.a.

 

Sampling location: Mühlweiher Litzelstetten

 

Phylogenetic tree: Cosmarium boeckii

 

Diagnosis: 

  • semi-cells almost semi-circular, flattened apices
  • length 30–40 µm, width 28–38 µm
  • basal angles rounded
  • apices with 4–5 flat undulations
  • closed sinus, outside widened
  • cell wall with marginal rows of papillae
  • in the center of semi-cell 4 papillae arranged in diamond shape
  • one pyrenoid per semi-cell
Cosmarium-boeckii
Cosmarium boeckii

I found Cosmarium boeckii in several specimens in July 2025 in the Mühlweiher Litzelstetten. There, the specimens were found growing on floating aquatic plants.

 

The identification of Cosmarium boeckii is essentially achieved by the 4 papillae, which are located in the middle of the semi-cells and arranged in a diamond shape. However, these are not easy to recognize in living specimens. They were best seen in my specimens under brightfield illumination (s. fig. 2 b).

Cosmarium-boeckii

Fig. 1 a-b: Cosmarium boeckii. L = 36 µm. Two focal planes of a specimen found in July 2025 in the Mühlweiher Litzelstetten. Obj. 100 X.

Cosmarium-boeckii

Fig. 2 a-b: Cosmarium boeckii. L = 36 µm. The same specimen as shown in fig. 1 a-b in brightfield illumination. Note the 4 papillae in the center of the semi-cells arranged in a diamond shape (arrowheads). Obj. 100 X.

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