Staurastrum margaritaceum

Meneghini ex Ralfs, 1848

Most likely ID: n.a.

 

Synonym: n.a.

 

Sampling location: Sima Moor (Austria)

 

Phylogenetic tree: Staurastrum margaritaceum

 

Diagnosis: 

  • cells about as wide as long, semi-cells bell-shaped
  • length 24–30 µm, width 24–28 µm
  • shape highly variable with 3–6 arms
  • arms projecting horizontal
  • two rings of warts on each side of isthmus
  • distal ends of arms with inconspicuous spines
  • apices convex with concentric rings of small warts
  • each semicell with one axial chloroplast, each with one pyrenoid
  • spherical nucleus positiones in the isthmus
Staurastrum-margaritaceum
Staurastrum margaritaceum

Staurastrum margaritaceum is a very variable species, which usually has a three- or four-fold symmetry in apical view. However, there are also specimens with a five- or six-numbered symmetry (s. drawings above). Common to all varieties, however, are short or absent spines and convexly curved apices. In addition, there is a ring of small warts on both sides of the isthmus.

 

Of all the described substspecies, the specimen shown below is most similar to form „e“ (s. drawing above). The four arms have no spines at the distal end, but only inconspicuous warts.

 

I found Staurastrum margaritaceum in large numbers in the Sima Moor (Austria) in June 2024. All specimens had a four-armed symmetry and had no spines, only warts.

Staurastrum-margaritaceum

Fig. 1 a-d: Staurastrum margaritaceum.  L =28 µm. Four focal planes in lateral view. Note the ring of warts (RW) on both sides of the isthmus. Nu = nucleus, PY = pyrenoid. Obj. 100 X.

Staurastrum-margaritaceum

Fig. 2 a-b: Staurastrum margaritaceum. The specimen as shown in fig. 1 a-d in apical view. The warts on the apices as well as at the distal ends of the four arms are small and inconspicuous. Obj. 100 X.