Staurastrum pileolatum. Notice rectangular cell with very shallow sinus, concave sides and broadly rounded angles.
Cell dimensions (L x B): 40 x 20 µm
Conjugated cells of Staurastrum pileolatum with a globose, spiny zygospore in between.
Staurastrum pileolatum, detail of (another) zygospore furnished with bi- and trifid spines.
St. pileolatum belongs to a group of Staurastra characterized by cells that are hardly constricted and about cylindric in shape*. Semicells in St. pileolatum are about rectangular in outline with concave lateral margins, a strongly retuse apex and broadly rounded angles. Cell wall sculpturing in the form of (emarginate) verrucae set in an isthmial ring and some concentric series around the apical angles. Zygospores are globose and furnished with stout, bi- or trifid spines**. St. pileolatum has its main distribution in relatively cold, upland regions. In the Netherlands, St. pileolatum was only very recently discovered**.
* occasionally accounted a separate genus, Cylindriastrum (Palamar-Mordvintseva 1976)
** see: Van Westen, M., 2015. Taxonomic notes on desmids from the Netherlands. — Phytotaxa 238: 230-242.
Empty semicell of St. pileolatum in apical view showing triradiate configuration (apical angles somewhat produced).
Same empty semicell of St. pileolatum in isthmial view showing a whorl of pronounced verrucae encircling the base of the semicell.
Empty cell of Staurastrum pileolatum in frontal view showing cell wall sculpturing in the form of an isthmial whorl and some concentric series of verrucae around the apcal angles.