Lesquereusia spiralis

Lesquereusia spiralis, with dark colored mucus surrounding the collar

Lesquereusia spiralis (Ehrenberg, 1840)

Diagnosis: test colorless, circular or ovoid with an asymmetrical neck, slightly flattened laterally and composed of numerous siliceous curved rods interspersed with a meshwork of organic cement. Organic cement matrix between the rods has a distinctive rosette-like pattern. Neck prominent, sharply turned to ones side. Aperture terminal, circular and bordered by siliceous rods.

Dimensions: Length of shell 89-120 µm, breadth of shell 86-109 µm.

Habitat: in Sphagnum and detritus, feeding on diatoms and green algae.

Remarks:D. modesta and D. spiralis are sometimes hard to distinguish from each other and I am not sure if both species are really different species.

Reported as Lesquereusia spiralis, but Lesquereusia is an incorrect, though widely used, emendation of the original genus name.

I have often found Lesquereusia spiralis with a black violet area around the aperture (see specimen above). I have found this specimens abundant in Sphagnum pools at two locations west of the town of Hilversum (Netherlands): het Hol near Kortenhoef and a peat bog along the Bert Bospad in Loosdrecht. The specimens seem to be covered with a layer of mucus.

Lesquereusia spiralis, and L. modesta, typical forms

L. spiralis, both specimens from the same location (pictures stacked from several photographs)

Lesquereusia spiralis (stacked image) with a test composed of mineral plates and long thin needles. Some needles are clearly radial spines from heliozoa (see the the detailed images)