Cosmarium orthostichum Lundell, 1871
Most likely ID: n.a.
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Synonym: n.a.
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Sampling location: Schwemm Moor (Austria)
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Phylogenetic tree: Cosmarium orthostichum
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Diagnosis:Â
- semi-cells ellipsoid, apices flat, sides convex
- length 36–37 µm, width 31–33 µm
sinus deep, laterally widened
cell wall with transverse rows of warts - paired warts near central field
- one chloroplast with one pyrenoid per semi-cell
So far, I have only found a few specimens of Cosmarium orthostichum in the Schwemm Moor in Austria. Lenzenweger (1999) also reports that this alga occurs only sporadically.
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The essential characteristic of Cosmarium orthostichum is the paired, sometimes even triple, warts in the central field of the semi-cells (s. fig. 1 c). However, this feature can only be recognized at high magnification. The size seems to lie within a very narrow range. Lenzenweger gives a length of 36–37 µm, while my specimens were mostly 38 µm long. This therefore also seems to be a fairly constant characteristic of Cosmarium orthostichum.
Fig. 1 a-c: Cosmarium orthostichum. L = 38 µm. Three focal planes of a slightly squashed specimen. Note the paired warts in the central field of the semi-cells (arrows). Obj. 100 X.
Fig. 2 a-c: Cosmarium orthostichum. L = 38 µm. The same specimen as shown in fig. 1 a-c in brightfield illumination. Obj. 100 X.