Diagnosis: Shell organic, yellow till brown or brown-grey, hyaline, without xenosomes, sometimes with some spines; in dorsal view more or less circular, in lateral view half spherical or flattened; aperture more or less centrically located, tubular invaginated, with 2-5 bridges.
Dimensions: 35-48 µm (Penard), mean 48 (Hoogenraad & De Groot); my measurements 48-54 µm.
Ecology: Sediment of ditches, between waterplants, in Sphagnum.
Remarks: This species is easy to identify. Hoogenraad & De Groot (1940) noted that this small species has been observed in the Netherlands only once, in 1908. I have found it with regular intervals, but never abundant.
Centropyxis delicatula, – the Netherlands
Centropyxis delicatula, 49 µm in diameter, stacked – Netherlands
Centropyxis delicatula, 48 µm in diameter
Centropyxis delicatula, Wannsee, Berlin
In an interesting paper, “Aquatic organisms as amber inclusions and examples from a modern swamp forest” (2007), Alexander R. Schmidt and David L. Dilcher show a photomicrograph (see above) of the shell of Centropyxis delicatula, embedded in modern tree resin (A) and 100-million-year-old Cretaceous amber from Schliersee, Germany (B).
Shell 46 µm and 54 µm – Simamoor, Austria
Centropyxis delicatula in side view – 48 µm in diameter
Centropyxis delicatula in side view – 49 µm in diameter
Centropyxis delicatula, with different number of bridges
Centropyxis delicatula – drawing: Ferry Siemensma
Centropyxis delicatula in side view – 50 µm in diameter