Cosmarium botrytis

Meneghini ex Ralfs, 1848

Most likely ID: n.a.

 

Synonym: n.a.

 

Sampling location: Simmelried, Botanical Garden Darmstadt, Pond of the convent Hegne, Ulmisried  

 

Phylogenetic tree: Cosmarium botrytis

 

Diagnosis: 

  • semi-cells oval trapezoidal
  • apices flattened, slightly convex
  • length 56–111 µm, width 48–85 µm
  • sinus deep, narrow, slightly dilated internally
  • lateral convex margins with warts
  • cell wall with small warts
  • pores between warts
  • two pyrenoids per semi-cell
Cosmarium-botrytis
Cosmarium botrytis

Cosmarium botrytis is a very common species that I find in several of my sampling sites. It has a characteristic appearance because the two pyrenoids per semi-cell sit in protrusions of the chloroplast, giving the impression that they are sitting on stalks (s. fig. 1 a and 2 a). The convex lateral margins are covered with warts, while the apices are strongly flattened and smooth. If you focal plane is on the cell wall, distinct pores between the irregularly distributed warts can be seen (s. fig. 1 b and 2 b).  

Cosmarium-botrytis

Fig. 1 a-b: Cosmarium botrytis. L = 108 µm. Focal planes on the pyrenoids (a) and the pores of the cell wall (b). Obj. 60 X.

Cosmarium-botrytis

Fig. 2 a-b: Cosmarium botrytis. L = 108 µm. The same specimen as shown in fig. 1 a-b in brightfield illumination. Obj. 60 X.

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