Desmid of the month
September 2008

Actinotaenium cucurbita

Actinotaenium cucurbita is characterized by more or less cylindric cells, broadly rounded at the apex, and  by stelloid chloroplasts incorporating a central pyrenoid. An important additional feature is found in the marked pore fields easily to be distinguished in empty cells, even at low magnification.

In the Netherlands (and elsewhere in Europe) A. cucurbita is one of the most common desmid species in acidic, oligotrophic bogs. It may stand desiccation for longer periods, so may also be encountered in emerse Sphagnum hummocks and on wet substrates that dry out periodically.

Image © Marien van Westen

Actinotaenium cucurbita. Notice the stelloid chloroplasts (one per semicell) each of them incorporating a big, globular pyrenoid.

Cell dimensions (L x B): 40 x 20 µm

Image© Marien van Westen

Empty cell of A. cucurbita. Notice the marked pore fields, equally distibuted over the cell wall.

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

SEM picture of an A. cucurbita cell showing cell wall sculpture at higher magnification.

mouse over:

SEM close-up of part of the cell wall (near the isthmus) showing pore fields in more detail. Each cell wall pore is situated in the centre of a crater-shaped pore field.