Euastrum crassum
Mouse over image © Alfred van Geest

Euastrum crassum (var. crassum). Notice deep median invagination of the apical lobe, faintly incurved lateral sides and a transversal series of three pronounced basal tubercles in each of the semicells.

Cell dimensions (L x B): ca 150 x 75 µm

 

 

Desmid of the month
December 2012

Euastrum crassum

Euastrum crassum somewhat resembles Eu. oblongum but differs by less differentiated lateral sides which are only faintly incurved. It also differs in its ecological demands. Whereas Eu. oblongum finds optimal conditions in slightly acidic, mesotrophic habitats, Eu. crassum is only encountered in distinctly acidic, oligotrophic water bodies, particularly in bog pools with a slight input of minerals. In the Netherlands, that kind of habitat has been destroyed on a large scale so that Eu. crassum is to be considered an endangered Red-List species.

Euastrum crassum in lateral view
Mouse over image © Alfred van Geest

Cell of Euastrum crassum in lateral view. Notice median inflation of the semicell.

Euastrum crassum, SEM image
SEM image © Jan Šťastný (after Austrian material)

SEM picture of Euastrum crassum. Notice marked cell wall pore fields with an extra deep scrobicle in the semicell centre.

 

Euastrum crassum var. microcephalum
Image © Jan Šťastný (after Irish material)

Cell of Euastrum crassum var. microcephalum differing from the nominate variety in that it has a smaller, less pronounced apical lobe.

 

SEM image of Euastrum var. microcepalumImage © Jan Šťastný (after Irish material)

SEM picture of Eu. crassum var. microcephalum. The cell in question shows less marked pore fields and some four scrobicles in the semicell centre, but those features are not characteristic of this particular variety.