Two cells of Penium margaritaceum. Chloroplasts are provided with longitudinal ridges. Between the chloroplasts big vacuoles are to be distinguished (dark-coloured in the upper cell).

Cell dimensions (L x B): ca 120 x 25 µm.



Desmid of the month
March 2004

Penium margaritaceum

The genus Penium is characterized by, among other things, cylindrical cells and distinct girdle bands in the cell wall. The outside of the wall shows a pattern of more or less regularly arranged granules or longitudinal ridges (Kouwets & Coesel, 1994). In Penium margaritaceum cell wall sculpture consists of minute, scattered granules. In the Netherlands it is a rare species and usually only a few cells per sample are encountered. However, last July it was occurring as predominating species in a shallow, recently excavated sand pit near the village of Crailo. Remarkably, many of the cells were dead and empty, showing a gap in their wall which was obviously caused by some unknown predator. 


Kouwets, F.A.C. & P.F.M. Coesel1984. Taxonomic revision of the conjugatophycean family Peniaceae on the basis of cell wall ultrastructure. — Journal of Phycology 20: 555-562.

Dead, empty cell of Penium margaritaceum. Cell wall shows distinct girldle bands as well as a sculpture of scattered granules. Upper left of the centre there is a gap in the wall caused by some predator, possibly the aggresive amoeba 'Vampyrella'.