Desmids: Giants and Dwarfs

Although, in general, cell dimensions of desmids are larger than those in most other unicellular algal groups, there are huge differences between the various species.

The smallest species are less than 10 micrometer in length (1000 µm = 1 millimeter), such as Actinotaenium geniculatum, an acidophilous desmid that is usually associated with peat moss.

image on the right:

Short cell chains of Actinotaenium geniculatum  settled on cells (alternating green, living cells and dead,  hyaline cells) of a Sphagnum leaf. The Actinotaenium geniculatum cells figured measure about 8 x 5 µm.

image © Henk Schulp

(find site: ‘Hatertse vennen’, The Netherlands)

left:

detail with Actinotaenium geniculatum

Extremely long cells may be found in species of the genera Closterium and Pleurotaenium.  For instance, Closterium turgidum and Pleurotaenium nodulosum may attain a cell length of more than a millimeter (>1000 µm).

image © Henk Schulp

(find site: ‘De Haak’, The Netherlands)

left:

Two paired cells of Xanthidium octocorne (recently having undergone division) next to the cell apex of Pleurotaenium coronatum (var. robustum). Cell dimensions (length x breadth) of X. octocorne are ca 25 x 20 µm (excluding spines); of P. coronatum ca 600 x 55 µm.

image on the right:

Micrasterias laticeps (ca 100 x 160 µm) next to a small, unidentified Staurastrum species (in apical view) and a filamentous colony of Teilingia granulata (cell size ca 7 x 7 µm)

Micrasterias torreyi (var. curvata), ca 300 x 200 µm, together with Micrasterias abrupta, ca 50 x 50 µm (at the margin of the image, not quite in focus)