Difflugia binucleata Penard, 1902
Diagnostics: Test ovoid with a distinct neck, thus resembling a vase. Test mainly composed of fragments of diatom shells, embedded in an organic matrix. Test often with adhering debris and therefore hard to detect between sediments. Always two vesicular nuclei present. Color yellow till brown.
Dimensions: Penard length 100 – 135 µm; my measurements 130 – 216 µm, mean 152 µm.
Ecology: mesotrophic watertype; debris in Sphagnum pools and between aquatic plants in ditches with Sphagnum contact. A rich population is present in the pond of Crailoo, the Netherlands.
Remarks: In 1904 Penard described this remarkable species (see his drawing below). As main characteristic he mentions the presence of two nuclei, hence the name. Another remarkable fact is that the test of this species is covered with a loose layer of debris, mainly around the neck and aperture. Therefore the shell might be hard to detect for non-specialists. The test has a distinct collar with a distinct neck. The test is mainly composed of fragments of diatom tests.