Penardeugenia bathybioticus

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.

References: Dumack, K., Siemensma, F., Bonkowski, M., 2018. Rediscovery of the Testate Amoeba Genus Penardeugenia (Thaumatomonadida, Imbricatea). Protist, 169, 1, 29-42.

The membrane contains numerous small scales.

Flexible aperture (arrowheads)

This specimen is probably dead.

Rounded specimen with nucleus visible

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.