Desmid of the month
May 2009

Euastrum binale

Euastrum binale, in particular its var. gutwinskii, is one of the most common desmid species in acidic, oligotrophic moorland pools and bogs. Despite the small dimensions and a lack of conspicuous cell wall ornamentation it may be readily recognized. Semicells are trapezoid-pyramidal in outline with a slightly dilated apex marked by acute angles and a wide, shallow, V-shaped median incision. Var. gutwinskii differs from the nominate variety by having an additional lateral lobe in between the basal and the apical lobe. Zygospores are only incidentally encountered.

Image © Marien van Westen

Euastrum binale var. gutwinskii. Notice the somewhat pyramidal semicell outline and the wide, V-shaped apical incision.

Cell dimensions (L x B): ca 25 x 20 µm

Dichotypical cell of Eu. binale. The upper semicell is characteristic of the nominate variety, the lower one rather of var. gutwinskii.

SEM picture of Eu. binale var. gutwinskii showing scrobiculation of the cell wall in a zone around the slightly inflated centre of the semicell (mouse over).

Image: Hanny Kooijman-van Blokland © IBED (mouse over)