A light and electron microscopical investigation of Ochromonas sphaerocystis Matvienko (Chrysophyceae): the statospore, vegetative cell and its peripheral vesicles

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Abstract
Vegetative cells of Ochromonas sphaerocystis Matvienko are examined by light and electron microscopy. The ultrastructure is generally typical for the Chrysophyceae although the nucleus has a sheet-like evagination which penetrates between the two chloroplast lobes and which is surrounded by a pyrenoid. There are numerous vesicles, approximately 1 μm diam. at the periphery of the cell. These stain with Sudan Black B, but not with methylene blue, brilliant cresyl blue or Sudans III and IV. An electron dense amorphous material appears adjacent to the membrane when fixed with osmium tetroxide. Statospore formation involves retraction of extracystic cytoplasm, including the chloroplast. The fully formed statospore has a thick neck with a recurved collar. Ochromonas sphaerocystis is compared with O. crenata Klebs and is concluded to be a separate species.