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Rhizamoeba timidum
Rhizamoeba timidum, characteristic shape, covered with detritus

 

Rhizamoeba timidum (Bovee, 1972) Siemensma, 1987

Diagnosis: Small amoeba, which can spread very flat with numerous pseudopodia; pseudopodia conical or blunt; polypodial form usually covered with a layer of detritus; monopodial form ovoid-shaped or more elongated; nucleus spherical with central nucleolus; cytoplasm clear, with many very small granules; one large contractile vacuole; hyaloplasm at the anterior end with eruptive bulges; hyaloplasm may run back along the sides.

Dimensions: my measurements: monopodium 42-100 µm, polypodial form 35-60 µm; nucleus 6.5-8.0 µm.

Ecology: Fresh water. I found this species several times in the Netherlands.

Remarks: It is possible that this species can be split in more than one species. One location showed several specimens which strongly resembled R. timidum, but with a much larger nucleus, 9.6-12 µm.

Rhizamoeba timidum
Rhizamoeba timidum with broad lamellapodium
Rhizamoeba timidum
This specimen moves from its polypodial shape into the monopodial from, leaving the detritus behind.
Rhizamoeba timidum
Broad monopodial form; nucleus visible and uroid with trailing filaments.
Rhizamoeba timidum
Rhizamoeba timidum
The same specimen, in phase contrast and in DIC.
Rhizamoeba timidum
A specimen leaving its covering of debris. Note the trailing filaments.
Rhizamoeba timidum
Rhizamoeba timidum, flattened polypodial form, covered with detritus.
Rhizamoeba timidum - Ferry Siemensma
Rhizamoeba timidum – Drawing: Ferry Siemensma, 1987
Rhizamoeba timidum
Rhizamoeba timidum – Drawing: Ferry Siemensma, 1987
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