Haplotaenium rectum. Notice the lack of an apical vacuole and the shallow but nevertheless distinct sinus.

Cell dimensions (L x B): ca 330 x 20 µm



Desmid of the month
March 2013

Haplotaenium rectum

Like Haplotaenium minutum H. rectum differs from representatives of the genus Pleurotaenium by an axial (not parietal) chloroplast and the lack of an apical vacuole. Compared with H. minutum, H. rectum is characterized by larger cell dimensions and a distinctly marked sinus. Like H. minutum it is confined to acidic, oligotrophic habitats. In the Netherlands, H. rectum is a rather rare species.

Haplotaenium rectum, detail of cell apex. Notice perfectly smooth cell wall, central row of pyrenoids (characteristic of an axial chloroplast) and lack of an apical vacuole.