Euastrum humerosum image © Henk Schulp

Euastrum humerosum var. humerosum

Cell dimensions (L x B): ca 130 x 70 µm

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Desmid of the month
March 2006

Euastrum humerosum

Like Euastrum oblongum Euastrum humerosum belongs to the group of Euastrum species in which the median apical incurvation is in the form of a deep, closed invagination. Semicells are about pyramidal in outline with rather deep incurvations separating apical, lateral and basal lobes. The basal lobes in their turn are incurved too, so more or less doubled. In the Netherlands both the nominate variety and var. affine (characterized by deeper lateral incurvations) are of occasional occurrence in acidic, oligotrophic moorland pools.

Euastrum humerosum var. affine image © Henk Schulp

Euastrum humerosum var. affine

Notice the somewhat dilated apical lobe and the pronounced lateral lobes (like hunched shoulders) characteristic of this variety.

Empty cell of Eu. humerosum var. affine well showing its cell wall sculpturing.

Notice a marked pit in the centre of the semicell with on either side a prominent tubercle. Three similar tubercles in transversal line are at the base of the semicell.