Extended Observation Descriptions

Amoeboid Protists
Naked Amoebae
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- Saccamoeba limax
Testate Amoebae
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- Pyxidicula operculata
Heliozoic Amoebae
Algae
- non-flagellous -
Chlorophyta
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- Chlorella spec.
- Eremosphaera viridis
Streptophyta (Desmidiaceae)
Ciliates
- Ciliophora -
Prostomatea
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- Coleps hirtus
OIigohymenophorea
Diatoms
- Bacillariophyta -
Coscinodiscophyceae
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- Melosira lineata
METAZOA
Cnidaria
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- Hydra viridissima
Rotifera
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- Ptygura kostei
- Ptygura longicornis

Extended Observation Description on Saccamoeba limax

Saccamoeba limax (Dujardin, 1841) Page, 1974

Taxonomic description in the Encyclopedia of Life

Link to the corresponding entry in Protisten.de

Naked Amoebae Hunting for Pyxidicula

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 Fig. 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.

Fig. 1: Saccamoeba limax in floating form with vesicular nucleus (arrowhead), crystals (arrowhead outline), food vacuole (double arrowhead) and the uroid (arrow).
Fig. 2–6: Phagocytosis of Pyxidicula operculata by Saccamoeba limax.
Scale bars indicate 25 µm.

Fig. 7: Saccamoeba limax with two ingested Pyxidicula cells (arrows). The contractile vacuole (arrowhead) is surrounded by large crystals typical for Saccamoeba limax.
Scale bar indicates 25 µm.

Fig. 8: Saccamoeba limax. Representation of the contractile vacuole and the uroid (arrowhead). The engulfed Pyxidicula cell has a nucleus that still appears intact (arrow).
Scale bar indicates 25 µm.

Like Pyxidicula operculata, this species has a vesicular nucleus with a relatively large central nucleolus. Both components of the karyoplasm show no granules. In the cytoplasm of the naked amoeba, other larger components can be seen: rhombic and bipyramidal crystals as well as food vacuoles. In Fig. 6, the contractile vacuole can also be seen and at the right rear end of the cell, an empty Pyxidicula shell can be seen, which had been excreted shortly before the photograph was taken.

Fig. 7 and 8 show other Saccamoeba cells. In the cell body of the amoeba from Fig. 7, two Pyxidicula shells can be seen (arrows). The specimen in Fig. 8 has engulfed a Pyxidicula cell, the digestion is apparently not very far advanced, at least the cell nucleus of the Pyxidicula still appears intact (arrow). On the uroid (arrowhead), the shaggy cell region that is dragged along during movement, two shells excreted shortly before the picture was taken are attached to plasma threads.

Fig. 9: Saccamoeba limax in its elongated locomotive form.
Scale bar indicates 25 µm.

Fig. 10: Saccamoeba limax when changing moving direction.
Scale bar indicates 25 µm.

The different forms of appearance of Saccamoeba limax

When the naked amoebae presented here are in the phase of locomotion on substrate, they show an elongated, monopodial shape with a appr. round cross section and a fine warty uroid. When changing direction, a Y-shape often results.

As the above images (Fig. 1 and 10) show, Saccamoeba limax can change shape from star-shaped (which also represents the floating shape in open water) to oblong up to pear-shaped. It should also be noted that in some manifestations the uroid is only partially visible.

© Wolfgang Bettighofer,
images under Creative Commons License V 3.0 (CC BY-NC-SA).
For permission to use of (high resolution) images please contact postmaster@protisten.de.

Protisten.de

Extended Observation Description on Saccamoeba limax

Naked Amoebae Hunting for Pyxidicula

The different forms of appearance of Saccamoeba limax

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