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Darbyshirella
Darbyshirella species, Dordogne river, France

Genus Darbyshirella Berney, Bass & Geisen, 2015

Diagnosis: Multinucleate, highly branching and reticulate naked amoebae with slender, pointed, sometimes branched pseudopodia. The whole cell body is strongly branching and of narrow width, especially in the most extended parts, while more condensed parts are wider. Pseudopodia and branches are usually formed when cells condense in the anterior extending regions, resulting in up to three new branches. Posterior end usually pointed with no or few pseudopodia and no branching. Anastomoses occur randomly between branching parts of the cell body that come into contact, leading to networks of varying complexity. Very elongated amoebae are often less reticulate than more condensed ones. Many contractile vacuoles present in the entire cell. Movement of entire cells too slow to be directly observable. Cysts present, varying both in size and shape.
Type species: Darbyshirella terrestris.

Diagnosis: Non-marine, with morphological characteristics of the genus. Usually above 600 µm in length. Cell body often narrower than 2 µm, more condensed parts up to 30 µm. Cysts with two clearly separate walls, spherical, oval or bean-shaped, varying between 10-40 µm in diameter. Mainly bacterivorous, but some cells may ingest small eukaryotes.

Ecology: Soil

Photomicrographs: I found the species from the photomicrographs on this page in a wet mount kept for some days in a moisture chamber. The sample came from sediments in the river Dorgdogne in France. At first I found one plasmodium, but within some days several specimens came up in a corner under the cover glass. Some specimens were attached to the glass slide, some others to the cover glass. The plasmodia moved very slowly and didn’t show any reaction to the light of the microscope. The plasmodia were roughly V-shaped, with many fine filopodia at the broadest part.
All specimens were about 250 µm large with about six nuclei, which were broad oval, 8-9 µm large, and with an irregularly shaped nucleolus, varing in shape from nearly spherical to a thin sheet.
The plasma was filled with rod-like structures, moving in bidirectional way. These structures are no granules as seen in foraminifera.There were many contractile vacuoles present.
In the same area where the plasmodia were active, some cysts appeared. I’m not sure if these cysts belong to the plasmodia. The cysts were spherical to oval, with a a somewhat crenulated outer layer.

Probably a cyst
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