Rhizamoeba coerulea – Microworld

Rhizamoeba caerulea, about 130 µm large, with at least two nuclei, one elongated oval and the other one more spherical.

Rhizamoeba caerulea (Schaeffer, 1926) Siemensma, 1987

Diagnosis: Medium-sized to large amoeba, which can spread very flat with very fine subpseudopodia, sticked to the substrate; polypodial form usually covered with detritus; monopodial form bat-shaped; numerous, up to 32 small nuclei; cytoplasm clear, with many very small granules and some elliptical crystals; several contractile vacuoles; hyaloplasm at the anterior end with eruptive bulges; hyaloplasm may run back along the sides.

Dimensions: My measurements 150—260 µm, nuclei 4.8—24.0 µm (Penard 5-7 µm). Schaeffer (1926): 150 µm.

Ecology: Freshwater.

Geographical distribution: In a stream near Epe (1980) and in a pond at Groeneveld (2012), both in the Netherlands. All amoebae were collected from floating detritus.

Remarks: It is possible that this species is identical to R. clavarioides.

Rhizamoeba species are very sensitive for light. This one started to retract its pseudopodia immediately when it came into the light path of the microscope.

Nuclei, 15 µm and 11 µm, each with two peripheral nucleoli.

The same cell as above after two weeks in a moisture chamber. It is also retracting its pseudopodia.

Rhizamoeba caerulea, 130 µm

Rhizamoeba caerulea A-B. polypodia; C-D transition from polypodium to monopodium; E. monopodium; F. floating form. After Siemensma, 1987.

Rhizamoeba caerulea A-C. monopodia; D. flattened form on agar; E-G. development of pseudopodia; nuclei, drawn in their internal relationship.- After Siemensma, 1987

Ferry Siemensma, created February 27, 2019; last modified June 09, 2026