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Difflugia sp.
D. yorkui, 273-307 µm (Naardermeer)

Difflugia yorkui Nicholls, 2007

Diagnosis: Shell large, elongated oblong, usually with a distinct neck and covered with large and irregularly shaped siliceous particles except in the anterior region where particles are very small; test roughly circular (not compressed) in transverse cross-section, tapering towards both anterior and posterior ends from its widest point at about the middle of the test. Aperture relatively small and circular,  . Organic basal material of the test (cement) organized in an open-meshed pattern of pores 0.3-0.8 µm in diameter separated by ribs 0.2-0.4 µm in width. With zoochlorellae. Nucleus ovular, densely filled with numerous small spherical nucleoli.

Dimensions: Nicholls (2007): Length 305-370 µm; width 140-162 µm; aperture 50-63 µm in diameter (n=12); my measurements: Length 222-460 µm (mean 365 µm); width 118-200 µm; aperture 56-101 µm (n=39).

Ecology: Freshwater; Canada, Netherlands (Naardermeer and several other locations).

Remarks: The identity of the Dutch shells was confirmed by Nicholls (pers. comm., 2021)

Difflugia yorkui
D. yorkui, reworked after Nicholls, 2007
Difflugia sp.
D. yorkui, 292 µm – stacked image, (Naardermeer)
D. yorkui
D. yorkui, 326 µm – 428 µm, (Naardermeer), all from the same sample.
Difflugia sp.
D. yorkui, nucleus in squeezed cell. Notice the zoochlorellae and the ingested diatoms.
Difflugia sp.
D. yorkui, shell ratio Length / Width (n=39)
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