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.

Reference:
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.
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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

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

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

Closterium pusillum var. laticeps
Image © Henk Schulp