Desmid of the month
May 2010

Cosmarium ungerianum
var. subtriplicatum*

C. ungerianum var. subtriplicatum belongs to the group of granulate Cosmaria in which the granules are unequal in size and unevenly distributed over the cell wall surface. The apical angles are provided with series of marked, often brownish coloured, marginal and intramarginal tubercles. Similar, but generally somewhat smaller tubercles/granules are disposed at the basal angles and in a circular group in the semicell centre. Also between that central group and the semicell apex a distinct tubercle is located. In the Netherlands, C. ungerianum var. subtriplicatum itself is unknown but there are some records of the closely affiliated var. bohemicum, from oligotrophic moorland pools, more than half a century ago.

* Possibly, this variety is more related to Cosmarium triplicatum Wolle than to C. ungerianum (Nägeli) De Bary

Cosmarium ungerianum var. subtriplicatum. Notice the pronounced marginal and intramarginal tubercles at the apical angles as well as the single median, subapical tubercle characteristic of this variety.
Cell dimensions (L x B): ca 60 x 50 µm

DIC Image © Wim van Egmond (after Czech material)

Another cell of C. ungerianum var. subtriplicatum. Notice the brownish colour of the bigger tubercles at the apical angles.


Cell showing wall sculpture in centre of the semicells, i.e., brownish tubercles, each surrounded by a series of scrobicles (lightening in this picture).


Idem, detail.

Cosmarium ungerianum var. subtriplicatum SEM image


SEM image of C. ungerianum var. subtriplicatum


image ©Jan Šťastný