Cell of P. polymorphum showing a girdle band and fine, longitudinal striae on its wall.

Cell dimensions (L x B): ca 60 x 25 µm



Desmid of the month
January 2010

Penium polymorphum

Penium polymorphum is characterized by cylindric-oval cells and a cell wall that is furnished with closely-set, fine longitudinal striae. As in all Penium species, usually one or more girdle bands may be distinguished. Chloroplasts are provided with a number of marked, longitudinal ribbons and usually a single, central pyrenoid. In central Europe, P. polymorphum is rather common in acidic, oligotrophic peat bogs. Until now, it was not found in the Netherlands but as it is known from neighbouring Belgium and Germany it could be expected in the Netherlands too.

Another cell of P. polymorphum without a distinct girdle band. Image

Penium polymorphum
Image © Koos Meesters

Cell of P. polymorphum with two girdle bands.

SEM picture of a cell of P. polymorphum with two girdle bands. Near the apices the longitudinal striae on the cell wall pass into a network of anastomosing, broken and irregular ones.

Detail of the mid region of the cell showing striae as sharp ridges. Notice the mesh-like appearance of the cell wall in between, characteristic of the family of Peniaceae.

Mouse over: Detail of the cell apex.