Desmid of the month
November 2009

Closterium pusillum

Closterium pusillum is readily to be recognized by its small, thick-set cells with broadly rounded to truncate apices. Chloroplasts are bounded at the cell ends by a large, globular vacuole usually holding a single crystal.  Cell morphology, in particular length to breadth ratio, is most variable (Brook 1992). Cl. pusillum is a semi-atmophytic species characteristic of wet substrates and ephemeral puddles. In the Netherlands it is widely distributed and, like other desmid species with a comparable way of life, less rare than originally presumed.

Brook, A.J., 1992. The desmid Closterium pusillum Hantzsch from two terraqueous habitats, with observations on asexual spore production. — British Phycological Journal 27: 409-416.

Cell of Closterium pusillum. Notice the broadly rounded apices and the large terminal vacuoles incorporating a single crystal.

Cell dimensions (L x B): 35 x 7 µm

Closterium pusillum
Image © Henk Schulp

Another cell of Cl. pusillum showing terminal vacuoles situated at some distance from the apex.

Cell of Cl. pusillum var. laticeps differing from the nominate variety by capitate cell ends.

Closterium pusillum var. laticeps
Image © Henk Schulp