Figs 41–52.

Maryna umbrellata, light (46, 47) and electron microscopical (41–45, 48–52) structure of the cyst contents after staining with UL (42, 44) or bismuth (41, 45, 48) and in protease digested, unstained sections (43, 49–52); 41 – the thin endocyst and the cortex of the ciliate are electron-dense and sometimes separated by a narrow shrinkage space (arrow; cp. Fig. 32); 42, 44, 46, 47 – the cyst contents consists mainly of “spongy globules” and lipid droplets (47). The spongy globules, whose polygonal substructure is sometimes recognizable in the TEM (44, arrows) and after prolonged chromic acid treatment in the PAS reaction (46), consist of an electron-dense matrix and electron-lucent, structureless “holes” (42, 44). The lipid droplets and the cyst plasm (42, 44, asterisks) appear structureless; 45, 48 – when stained with bismuth, both the electron-lucent areas in and between the spongy globules and lipid droplets show a foamy structure, indicating the presence of polysaccharides. The matrix of the spongy globules shows a polygonal pattern, each polygon usually having an electron-lucent, foamy centre; 43, 49–52 – sections treated with protease for 25 min (43, 49–51) and 50 min (52) are much less electron-dense than ordinary sections (31–34, 49) because most substance of the mesocyst and the spongy globules has been digested. Mild digestion leaves back the contents of the “holes” of the spongy globules (43, 51) and, occasionally, the membranes surrounding their subunits (50). Strong digestion leaves back mainly the membranes (52). The lipid droplets have a proteinaceous centre (49, 51, 52). C – ciliate cortex, E – endocyst, EC – ectocyst, G – glass granules, L – lipid droplets, M – mesocyst, MT – mitochondria, SG – spongy globules. Scale bars: 500 nm (Fig. 48), 1 μm (41, 43, 44, 49), 2 μm (42, 45, 50–52), and 10 μm (46, 47).