Desmid of the month
October 2003

Closterium aciculare

Closterium aciculare, photographed in its natural environment.
Celldimensions (L x B): ca 500 x 7 µm

Closterium aciculare * is a typically planktonic species. Because of its high cellular surface to volume ratio sinking velocity is low. Particularly in big water bodies where there is always some water movement by currents or wave action cells are easily maintained in the water column. 

Culture experiments have shown that Closterium aciculare definitly needs ammonium as a nitrogen source; it cannot be grown in medium containing only nitrate (Coesel 1991). This    is an exceptional phenomenon amongst algae (and other plants) and may explain the rather unusual ecological distribution of Cl. aciculare. Whereas, in our temperate climatic region, most desmid species flourish in oligo-mesotrophic waters in summertime, highest population densities of Closterium aciculare are encountered in eutrophic waters, in spring or autumn. Particularly under those latter conditions relatively high concentrations of ammonium are to be expected (Coesel 1991).

* acicularis (Latin) = needle-shaped

Reference

Coesel, P., 1991. Ammonium dependency in Closterium aciculare T. West, a planktonic desmid from alkaline, eutrophic waters. Journal of Plankton Research 13: 913-922.

image © Peter Coesel

Cell of Closterium aciculare, grown in medium containing ammonium. The cell looks vital, shows a well-developed chloroplast (in which a series of pyrenoids is visible) and may divide readily.

image © Peter Coesel

Cell of Closterium aciculare, grown in medium without ammonium. The cell shows a highly contracted chloroplast (with an accumulation of starch) and is unable to reproduce.