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Actinosphaeridium

A. pedatus, drawing after Penard, 1903

Genus Actinosphaeridium Zacharias, 1893

Actinosphaeridium pedatus Zacharias, 1893
Syn.: Nucearia caulescens Penard, 1903

Diagnosis: Cell surrounded by a mucous layer. Filopodia with granules, sometimes branching. Cell stalked; stalk ends at the cell body. During cyst formation the cyst is covered with siliceous plates.

Dimensions: Cell body 16-20 µm, with mucous layer about 40 µm.

Ecology: Several specimens between wet moss in a small pond on an ecoduct near Crailoo, the Netherlands, February 2021, just one week after the ice had melted.

Remarks: I could not detect any mucous layer in my specimens. It was not visible in phase contrast, nor in DIC. The cells were surrounded by a thin membranous shell, which was hard to detect.

Actinosphaeridium

Actinosphaeridium pedatus
Actinosphaeridium
Habitus, branched pseudopodium
Actinosphaeridium
Cell with captured prey
Actinosphaeridium
Actinosphaeridium
“Foot” of the stalk, attached to the cover glass
Actinosphaeridium
Phase contrast
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