Motile cells of Pyramimonas species are covered with up to four
layers of submicroscopic scales made of polysaccharides. Details of scale
structure help separate Pyramimonas species from each other and
from species of Halosphaera.
The flagellate cell cytoskeleton is based on a subtly asymmetrical array of
four flagellar bases and four microtubular roots. The degree of
cytoskeletal asymmetry is one of the features that separates the subgenera.
The overall arrangement, especially in the subgenus Trichocystis,
closely resembles Halosphaera.
However, the "spline-MLS"
root system present in Halosphaera is missing from all Pyramimonas species. A Halosphaera-like duct system is
present, but the lumen of the duct is usually filled with scales (hence the
term "scale reservoir"), and there is no evidence that the duct is used to
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