Rhogostoma
Rhogostoma spec. with broad lamellipodium and retracting pseudopods

 

 

Rhogostoma spec.

 

Diagnosis: shell spherical, covered with small mineral grains; aperture is a small rectangular slit, invaginated; pseudopodia small digitate, usually extending from a broad lamellipodium.

 

Dimensions: shell c. 35 µm (n=20)>

 

Ecology: sediments of peatbog, the Netherlands.

 

Remarks: This amoeba came up in a wet mount kept for several days in a moisture chamber. The test is broadly ovoid and covered with small xenosomes. The pseudostome is a small slit, shaped as a rectangular hole. This pseudostome is perpendicular to the longitudinal axis of movement. The amoeba moves by means of a broad hyaline veil, with an irregular border on which small digipodia appear. The uroid is formed by some trailing filaments, which can be branched. No nucleus could be observed. About twenty cells were present in the mount. The sample came from the Bert Bospad. One week later I found a specimen in a sample from the Dammerkade, also in the Netherlands. Recently I found it in samples from Crailoo.
The veil is extremely thin and hard to detect in normal light. That could be the reason that this remarkable amoeba has been overlooked in the past.
This could also be a Capsellina species.

 

Rhogostoma
Rhogostoma
Cell moves to the left; arrow indicates direction of movement
Rhogostoma
Rhogostoma
Distinct slit<
Rhogostoma
Rhogostoma
Two shells with a more or less rectangular pseudostome.
Rhogostoma
Rhogostoma>
Rhogostoma
Rhogostoma
All four photomicrographs of the same specimen, Crailoo
Rhogostoma
Rhogostoma/div>

 

Rhogostoma
Detail of lamellipodium; note the dark lines of the digipodia in the veil.
Rhogostoma
Rhogostoma