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 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 varieties, the specimen shown below is most similar to variety 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.
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.
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.