Roya obtusa

The genus Roya belongs to the saccoderm desmids (Fam. Mesotaeniaceae). Per cell there is but one single, plate-like chloroplast that may be provided with longitudinal ridges. In the midregion of the cell the chloroplast shows a notch enclosing the laterally located nucleus. 

By far the most common species of this genus is Roya obtusa (including R. anglica that better be considered a variety of R. obtusa). Roya obtusa is characterized by slightly curved, cylindric cells with broadly rounded to truncate apices. Usually, the dorsal cell margin just below the apex is somewhat incurved. In the Netherlands Roya obtusa, in particular its var. anglica, is locally rather common on wet, oligotrophic, loamy or sandy substrates.

Image © Henk Schulp

Roya obtusa (var. anglica). The singular chloroplast displays a notch in the midregion where the cell nucleus is located.

Cell dimensions (L x B): 80 x 7 µm

 

<< Image on the left:

Another cell of Roya obtusa (var. anglica) showing on the left pole the slight subapical incurvation of the dorsal margin that is characteristic of the species.

Image © Henk Schulp