Cosmarium pericymatium

Cosmarium pericymatium belongs to a small group of desmid species that can stand long periods of severe drought (Brook 2001). With its thick-set cell shape (low cell surface to content ratio) and thick cell wall evaporation rate is reduced. At first glance cells not seldom seem to be smooth-walled and may remind of some species of the genus Actinotaenium, but at closer examination the subglobose semicells appear to be faintly and unevenly undulate at the margin.

C. pericymatium is known from wet moss cushions and shallow rain puddles, but also from garden ornaments periodically holding some water. In the Netherlands it was only rather recently discovered for the first time, i.e., amongst mosses growing on a sandstone statue located in Blijdorp Zoo (Rotterdam).

Reference

Brook, A.J., 2001. The drought-resistant desmid, Cosmarium pericymatium Nordstedt, and a description of the new var. corrugatum. — Quekett Journal of Microscopy 39: 127-132.

Cell of Cosmarium pericymatium characterized by  a shallow sinus, subglobose semicells with an unevenly undulate margin and stelloid chloroplasts.

Cell dimensions (L x B):  40 x 25 µm