Desmid of the month
September 2004

Cosmarium striolatum

C. striolatum* can hardly be confused with any other Cosmarium-species. The large, rounded-cylindrical cells are characterized by a slight median constriction and a very regular pattern of cell wall granules, arranged in transversal and oblique-decussate series. In Europe, the species in question is far from common. The Netherlands seem to be at the westernmost border of its distribution area, for C. striolatum was never recorded from the United Kingdom (Brook & Williamson, 1991). In the Netherlands until recently C. striolatum was only known from some moorland pools near the village of Oisterwijk where it was encountered by Prof. J. Heimans in 1916. However, June 2002 it was rediscovered in a number of mesotrophic quivering fen plots in the nature reserve ‘De Wieden’ (Coesel, 2004).

* Synonym: Cosmarium tesselatum

Image © Wim van Egmond

Detail of cell wall. The granules are arranged in transversal and oblique-decussate series; each granule  is surrounded by six cell wall pores.

References:

Brook, A.J. & D.B. Williamson, 1991. A check-list of desmids of the British Isles. Freshwater Biological Association, Ambleside, 40 pp.

Coesel, P., 2004. Bijzondere sieralgvondsten in ‘De Wieden’ (in Dutch, with summary in English). — Gorteria 30: 1-6.