Desmid of the month
January 2011

Cosmarium subprotumidum

C. subprotumidum belongs to a group of Cosmaria characterized by a granulate cell wall and a crenate cell outline. As compared to the lateral crenations the apex is more flattened and somewhat produced. Granulation is in the form of some three longitudinal series of granules in the semicell centre and a number of radiate series linked up with each of the peripheral crenations. Contrary to most desmid species, C. subprotumidum can be also met with in (slightly) alkaline waters. In the Netherlands it is a common species in meso-eutrophic water bodies like peat pits, fen hollows, ditches and ponds.

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Cell of Cosmarium subprotumidum in frontal view. Notice crenate lateral sides and more flattened apex.

Cell dimensions (L x B): 30 x 28 µm

Image © Chris Carter (after British material)

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Another cell, both in frontal and apical view. Notice cell wall granulation and central inflation of the semicell body (apical view in mouse over)

mouse over mages © Chris Carter

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A somewhat smaller cell (23 x 23 µm) from the Netherlands. Notice produced apex.

Image © Koos Meesters

Dead, empty cell of C. subprotumidum showing pattern of cell wall granulation. Notice three longitudinal series in the semicell centre, the exterior ones being bent in the form of an almost closed circle.

Image © Koos Meesters

SEM picture of C. subprotumidum showing the pattern of cell wall granulation in more detail.

Image Hanny Kooijman née van Blokland © IBED