Fig. 1

Morphology and ultrastructure of D. papillatum. A Scanning electron microscopy image. The anterior end of the cell exposes the two flagella emanating from the flagellar pocket (left), the cytopharynx (right), and the conspicuous lip-like papillum between these two openings. Measurements taken from this image (using the ImageJ software): cell length > 10.5 μm (the exact size cannot be measured from this image because the cell does not lie flat); cell width ~ 5.9 μm; flagella length 6.5 μm; and cytostome width 0.31 μm. B Expansion microscopy-based model showing the nucleus and mitochondrion of a typical cell. Light gray, cell-surface tubulin; cyan, reticulated mitochondrion; blue, reticulated nuclear heterochromatin. The three-dimensional model was built from the Z-stack series of images after staining with DAPI and anti-tubulin antibodies. For details see Additional file 1: Sect. 1. Physical structure and size of the Diplonema papillatum nuclear genome