Penardeugenia
Elliptical aperture through which filopodia and conopodia extend

 

 

Penardeugenia bathybioticus (Penard, 1904) Deflandre, 1958

 

I found this amoeboid in a sample from the river Weser in Germany October 2012. My first thought was a Rotosphaerid, because of the reddish color and carmine colored granules, and its relatively large nucleus. But its behavior resembled more that of a Cochliopodium. However, the amoeba never spreads out fully, as Cochliopodium-species do, but always extends its conopodia through an elongated, usually small, elliptical aperture. The amoeba is enveloped by a scale bearing and very flexible membrane. Though I have observed several specimens, I couldn't succeed in isolating one for SEM observations.

 

Penardeugenia
The membrane contains numerous small scales.
Penardeugenia Weser
Flexible aperture (arrowheads)
Penardeugenia
Penardeugenia
This specimen is probably dead.
Penardeugenia
Penardeugenia
Rounded specimen with nucleus visible
Penardeugenia

 

 

These drawings show the shape of the amoeboid, which is actually a pouch with a flexible aperture, varying in shape from broad oval to narrow elliptical.
Penardeugenia
Broad aperture
Penardeugenia
The same photomicrograph in black and white
Penardeugenia
Characteristic narrow elliptical aperture when moving along the substrate (direction South-West).

Penardeugenia

With food particles
Penardeugenia
Penardeugenia
Penardeugenia
Relatively large nucleus with small central nucleolus.