Image © Marien van Westen

Euastrum coeselii. Notice relatively broad, flat apex with slight median indentation as well as rounded semicell angles.

Cell dimensions (L x B): 17 x 13 µm


Image © Alfred van Geest

Another cell of Euastrum coeselii showing chloroplasts with a single, central pyrenoid.

Image Hanny Kooijman née Van Blokland © IBED

Another SEM picture of Eu. coeselii. Notice semicells with a distinct central tubercle surrounded by a semicircle of scrobicles.

 

 

Desmid of the month
April 2017

Euastrum coeselii

Euastrum coeselii, originally known as Eu. binale var. groenbladii, was raised to species level by Kouwets ( 1987). Compared to Eu. binale , semicells in Eu. coeselii are less trapezoid (i.e., with a boader apex relative to the base). Moreover, apical angles are less acute and the median apical indentation is hardly marked, sometimes even almost invisible. Semicell wall is provided with a central tubercle (sometimes much reduced) and a number of scattered fine pores often in combination with some scrobicles. Eu. coeselii may rather be confused with Eu. insulare. In last-mentioned species, however, the median apical indentation is more marked resulting in a dichotomy of the apical lobe. Moreover, Semicells of Eu. insulare show lateral lobes next to the basal lobes where those lobes in Eu. coeselii merge to single ones. In the Netherlands, Eu. coeselii is rather common in various mesotrophic water bodies.

Reference:
Kouwets, F.A.C., 1987. Desmids from the Auvergne (France). — Hydrobiologia 146: 193-263.

Image Hanny Kooijman née Van Blokland © IBED

SEM picture of Eu. coeselii showing scattered cell wall pores and semicells with a reduced central tubercle.