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 Pyxidicula operculata

Pyxidicula operculata (Agardh, 1827) Ehrenberg, 1838

Taxonomic description in the Encyclopedia of Life

Link to the corresponding entry in Protisten.de

Pyxidicula operculata as a Member of Neuston

The overview in Fig. 1 shows a bacterial lawn, a number of circular structures, which on closer inspection are hourglass-shaped, and naked amoebae. The small watch glasses turned out to be shell (testate) amoebae from the group of Arcellinida, genus Pyxidicula Ehrenberg 1938.

Fig. 2 to 5 show several optical sections through the observed cells. In the group of four in Fig. 2, the focus is on the level of the bacterial layer. In Fig. 3 the focus is on the nuclei. Fig. 4 presents the vesicular (ellipsoidal) nucleus with its large central nucleolus together with the contractile vacuoles, next to it an empty shell, where one can even see the fine granulation of the shell material (pseudochitin with sandpaper structure) and its beaded rim. In order to be able to display the surface structure of the shell material and the beaded rim equally sharply, several optical sections were combined using DOF image technology.

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

Fig. 1: Overview of the water surface membrane with bacterial lawn, shell amoebae and naked amoebae.
Scale bar indicates 100 µm.

Fig. 2: Pyxidicula operculata amoungst bacteria.
Scale bar indicates 10 µm.

Fig. 3: P. operculata, the lens is focused on the level of the nuclei (arrow) and the contractile vacuoles (arrowhead).
Scale bar indicates 10 µm.

Fig. 4: Pyxidicula with the typical vesicular nucleus and the two contractile vacuoles next to an empty shell (DOF image).
Scale bar indicates 10 µm.

Fig. 5: Detail of Fig. 3. Nucleus with extraordinary structured nucleolus.
Scale bar indicates 10 µm.

Fig. 6: Lateral view of a Pyxidicula showing the conical (v-shaped) pseudopodia (arrow).
Scale bar indicates 10 µm.

The aperture (the pseudostome, the shell opening) is almost as large as the shell diameter. The shells are shaped like a flattened hemisphere. Fig. 5 shows a rarely observed nucleus figure with the additional zone of aberrant optical density in the center of the nucleolus.

The larger dots in the cell plasma are mitochondria. A piece of chitin from a mosquito that hatched in the sample container and then accidentally fell into the water and died opened up the opportunity to photograph a Pyxidicula cell in lateral view (Fig. 6). The shell cross section and the aperture are clearly visible. The observer can discover the way of attachment to the substrate and the shape of the pseudopodia.

Some specimens of the sample resembled Pyxidicula patens in some morphological aspects, but the shell diameter was only half of the expected value. For further details on the sample shown here, please see Pycidicula spec. in arcella.nl.
Specimens of this sample were molecularly examined by Daniel G. Lahr in 2011 and were shown to belong to the species P. operculata (https://doi.org/10.1371/journal.pone.0022780).

© 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 Pyxidicula operculata

Pyxidicula operculata as a Member of Neuston

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