Fig 53.

Maryna umbrellata, transmission electron micrograph of a resting cyst, showing the cover of glass granules and many peculiar, white-spotted globules within the cyst. These conspicuous storage products are produced by unstained, tortuous strands of glycogen embedded in an electron-dense, proteinaceous matrix. Note that the volume of the thick cyst wall is, indeed, the same as that of the encysted cell. This demonstrates impressively the significance of the wall in the life cycle. Very likely, the wall does not only protect the cell from environmental stress but also plays an important role in the environment and in initiating the excystment process. The asterisk marks shrinkage space between the encysted cell and the cyst wall. BL – basal layer, E + C – ectocyst and cortex, G – glass granules, M – mesocyst, MA – macronucleus. Scale bar 50 μm.