Desmid of the month
August 2003

Desmidium swartzii

Desmidium* is one of the filamentous desmid genera characterized by rather firm intercellular connections: filaments are only to be disrupted by robust mechanical pressure. From the Netherlands some four species are known, of which Desmidium swartzii is the most common. Cells of this species are triangular in apical view. After cell division daughter cells stick together so that the filament in question increases in length. Moreover, cell filaments are markedly twisted, to be seen from a gradual shift in position of the cellular lobe facing the observer.

In case of conjugation (almost) all cells in the paired filaments are sexually activated, resulting into a series of zygospores coupling the empty cell filaments.

* The genus name of Desmidium - derived from the Greek word 'desmos' (= ribbon, chain or bond) - presumably gave rise to the family name of Desmidiaceae.

Disrupted filament showing some single cells in apical view (triangular)

Two cell filaments of Desmidium swartzii; notice helical twisting of the filaments

Cell dimensions (l. x br): ca 20 x 50 ┬Ám

Zygospore formation in Desmidium swartzii