Difflugia binucleata Penard, 1902
Diagnostics. Shell ovoid with a distinct neck, resembling a vase. It is primarily composed of fragments of diatom frustules embedded in an organic matrix, often accompanied by adhering debris, making it difficult to detect within sediment. Two vesicular nuclei are always present. The shell’s color ranges from yellow to brown.
Dimensions: Penard (1902): Shell length 100 – 135 µm; my measurements 130 – 216 µm, mean 152 µm.
Habitat: Mesotrophic watertype; debris in Sphagnum pools and between aquatic plants in ditches with Sphagnum contact. A rich population was present in the pond of Crailoo, the Netherlands.
Remarks: In 1904, Penard described this remarkable species (see his drawing below). A key characteristic he noted is the presence of two nuclei, which inspired its name. Another notable feature is the loose layer of debris covering the test, particularly around the neck and aperture, making the shell difficult to detect for non-specialists. The test features a distinct collar and neck and is primarily composed of fragments of diatom tests.
