Genus Darbyshirella Berney, Bass & Geisen, 2015
Diagnosis: Multinucleate, highly branching, and reticulate naked amoebae with slender, pointed, and occasionally branched pseudopodia. The entire cell body is extensively branched and typically narrow, especially in its most extended regions, while more condensed areas appear wider. Pseudopodia and branches usually form when cells condense in the anterior extending regions, often producing up to three new branches. The posterior end is generally pointed, with few or no pseudopodia and no branching.
Anastomoses occur randomly when branching parts of the cell body come into contact, creating networks of varying complexity. More elongated amoebae tend to be less reticulate than more condensed ones. Numerous contractile vacuoles are distributed throughout the cell. The movement of entire cells is too slow to be observed directly. Cysts are present and vary in both 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.
Habitat: Soil, freshwater.
Photomicrographs: I discovered the species shown in the photomicrographs on this page in a wet mount that had been kept for several days in a moisture chamber. The sample was collected from sediments in the Dordogne River, France. Initially, I found a single plasmodium, but within a few days, multiple specimens appeared in a corner beneath the cover glass. Some were attached to the glass slide, while others adhered to the cover glass. The plasmodia moved very slowly and showed no reaction to the microscope’s light.
The plasmodia were roughly V-shaped, with numerous fine filopodia extending from the broadest part. All specimens measured approximately 250 µm in size and contained around six nuclei. The nuclei were broadly oval, 8–9 µm in size, with irregularly shaped nucleoli that varied from nearly spherical to thin, sheet-like structures.
The plasma was filled with rod-like structures that moved bidirectionally. These structures were distinct from the granules typically observed in foraminifera. Numerous contractile vacuoles were present.
In the same area where the plasmodia were active, some cysts appeared. However, it is uncertain whether these cysts belonged to the plasmodia. The cysts were spherical to oval, with a somewhat crenulated outer layer.
