Difflugia nodosa (Leidy, 1879)
Diagnosis: Test large, robust, pyriform, compressed in cross-section; fundus with 1-4 blunt conical projections; zoochlorellae present; nucleus large, spherical with large and small granules.
Dimensions: Penard 350-420 µm long. My measurements: 317-522 µm, nucleus Ø 50-70 µm.
Ecology: I found numerous specimens in sediments of ditches around the nature reserve Naardermeer, in Gaasterland, Diepveen, Bert Bospad and in a forest pond at Groeneveld, all in the Netherlands. Locally not rare.
Remarks: This species was first described by Leidy (1879) as a variety of Difflugia (pyriformis) oblonga. Cash (1909) described a new species, Difflugia crassa, but this species is probably identical with Difflugia nodosa. The photomicrographs on this page probably show different species.
DNA-research (Blandenier et al., 2017) showed that D. nodosa is a cryptic morphospecies including at least two species.