Observation Descriptions on Saccamoeba limax

If sample water is left to rest in Petri dishes in the laboratory for a few days or weeks, a small, natural habitat can develop there. Samples from oligotrophic waters are particularly suitable for this method. With the dissecting microscope one can observe the protistic life in such microhabitats very well and transfer interesting objects with the pipette to a slide for more detailed examination. The following report deals with protists that are part of neuston (Preston, 2003), as they live on the surface membrane of the water body.

Numerous shell amoebae (testate amoebae) from the Arcellinida group, genus Pyxidicula, were moving on the underside of the surface membrane of the water, which was also covered with a bacterial lawn. In addition to the testate amoebae, a large number of naked amoebae of a certain species, each about 60 µm long, were living there. Strictly speaking, it is the hyponeuston, the community on the underside of the water surface, to which the amoebae belong. It is to be distinguished from the epineuston, the symbiotic community on the surface membrane; the organisms there (e.g. certain types of golden algae) are not surrounded by water.

The naked amoebae showed very different shapes, which I could not assign to one and the same species at first glance. After a longer period of observation, however, I had the opportunity to witness the transformation of the star-shaped resting form into the round and elongated moving form. The sequence Figure 1–6 shows this, as well as the phagocytosis of a pyxidicula cell by a naked amoeba.

Sample from Pond Suploch, Hiddensee (Germany) Latitude: 54.538638, Longitude: 13.097802.