Pseudamphitrema* (Work title)

Diagnosis: Shell colorless, tubular, circular in cross section, resembling the shape of a peanut, with two opposite pseudostomes; mid region of the test sometimes slightly smaller; shell wall rigid, organic with small encrusted xenosomes, tapering towards both apertures. Pseudostomes very small, but hard to observe because of an adhering bunch of xenosomes. Nucleus vesicular, with spherical nucleolus; nucleus eccentrically layered. Pseudopodia branching, but not anastomosing. In the filopodia some granules are present. Cytoplasm fills the shell nearly entirely. When the cell is moving, only one pseudostome emits pseudopodia. The other aperture doesn’t show filopodia during locomotion, but these can appear fast.

Dimensions: length 10.5-19.6 µm,  breadth 6.5-7.4 µm (n=6); nucleus 3.3 µm (n=2).
Specimens from Gaasterland: length 17.7-21.5 µm,  breadth 7.7-9.2 µm (n=2); nucleus 3.3 µm (n=2)

Ecology: fresh water, brackish water. I found this species in samples of Crailoo and Gaasterland (July, 2019), both in the Netherlands, and at three locations in France:

• small pool fed by rainwater along a forest road in the hills of Southern France near Hyères.(GPS 43.168849, 6.375886); it is dried up during summer time.
• small stream in a forest in the Valley of Traouiera between Trégastel and Perros-Guirec (Bretagne).
• old washing accommodation, with brackish water along the coast of Île-Grande (Bretagne); the pond is fed by rain water and incoming high tide (see photograph at the bottom).

Remarks: This species resembles in shape a Paramphitrema species, but the type of pseudopodia doesn’t agree with the descriptions of all known Paramphitrema species which usually have one or two flagellum-like filopodia which can branch. The filopodia of the species described here are much more branched, with short branches at right angles. They resemble the filopodia of Pseudodifflugia species.
This species shows some resemblance with P. muelleri, but that species has non-branching filopodia or filopodia which only branch at the aperture.
Sometimes the cell can be confused with Pseudodifflugia when only one aperture emits filopodia.