Frenzelina reniformis, at two diffferent levels
Frenzelina reniformis Penard, 1902
Diagnosis: test membranous, semi-hemispherical or hemispherical, usually with an open ventral face; very small mineral grains, loosely attached to the membrane; test in dorsal view usually elliptical; test not always present; plasmabody broad-elliptical or kidney-shaped; aperture flexible, commonly a short small tube; numerous fine filopodia, often in a bundle; nucleus vesicular with one central nucleolus.
Dimensions: 26-30 µm (Penard); my measurements: shell 18-33 µm.
Ecology: fresh water, in ditches and lakes, between sphagnum and debris. Very common.
Remarks: Naked specimens closely resemble Lecythium-species, which also have a flexible aperture. Naked cells can have a thick layer of mucous to which small particles adhere.
Empty shell, c. 33 µm
Drawing: from Penard (1902)
Two cells from the same location
Frenzelina reniformis, just like Penards drawing above (l) and cell attached to the cover glass (r)
Dividing specimen, without test; kidney-shaped specimen without test
Small cylindrical aperture and bundle of filopodia
Pseudostomal view; lateral view
Cells about 24 µm, almost naked. Both cells from the same wet mount.
Frenzelina reniformis, with filopodia, cell c. 28 µm.
Shell almost a complete sphere, with small pseudostome
The same specimen, changing its aperture within one minute.
Frenzelina reniformis naked form
Frenzelina reniformis, nucleus visible
Two naked specimens from the same wet-mount-culture. Notice the difference in size.
Frenzelina reniformis, 26 µm
Frenzelina reniformis, with small tubular pseudostome; body 22 µm