Description: The cell has a central body from which numerous granuloreticulopodia emerge. The cell body can be small or large, flat or cylindrical, with a rounded to an irregular and elongated one; the common shape is more or less sausage-shaped and elongated. The cell body can sometimes be branched or with holes, but only after migration. The cytoplasm always presented several adjacent opposite conspicuous flows. The granuloreticulopodia emerge from any part of the cell. There are of two types: a few large ones that can reach a length of over one mm and numerous thin ones that form an network (reticulum) all around the cell body and at the end of or parallel with the large granulopodia. All pseudopodia show a bidirectional movement of vacuoles, granules and food particles. The cell does not move as amoebae do, but migrates to a new location by transferring the whole cytoplasm through one large vein by unidirectional movement. The whole content of the cell, including organelles and nuclei, slowly flows out of the initial cell body into the new one. Contractile vacuoles are present in both the cytoplasm and the pseudopodia. Nuclei numerous, almost 1000 nuclei in a large specimen. Nuclei spherical with peripheral nucleolar material and some scattered granules throughout the nucleus. The cell captures prey with its thin thread-like granuloreticulopodia and transports it into the cell body. When stationary, the body is sausage-shaped. It does not move or relocate for many hours or even days. One specimen which was hidden in a cluster of debris, stayed there for three days before migrating to another piece of debris.
Dimensions: Cell body 350-1760 µm (n=2). Reticulopodium up to 4 cm in diameter. Nuclei 5.47-7.26 µm (mean=6.28 µm; n=60, measured in one specimen); number of nuclei: almost 1000 in a large cell.
Ecology: I found this large naked amoeboid when I was searching a Petri dish with material from the Crailoo pond. This specimen was sampled from organic sediment in the shallow part of the pond at Crailoo near the city of Hilversum, the Netherlands, January 2020. At home, I kept the material in a glass jar on a window sill in a not-heated room. I found this amoeboid after three weeks when searching some of this material in a Petri dish. In the same sample there were also some cells of Lacogromia cassipara present.
Remarks: This species is morphologically similar to H. saranae, but differs in the size of the nuclei (5.47-7.26 µm versus 2-4 µm for H. saranae).