body variable from cylindrical to club-shaped, straight or weakly bent, not flattened
in cylindrical form posterior and anterior end rounded, sides parallel
length 16–20 µm (of elongated cell)
one flagellum, almost of body length
distinct striation that spirals in counterclockwise direction
paramylon bodies elongate roundish to short rod-shaped
Astasia cylindrica
I found Astasia cylindrica in Simmelried in February 2017. During metabolic movement, this species adopts cylindrical shapes with almost parallel sides and rounded ends. This distinguishes it from all other Astasia species. Additional characteristics are the small size of about 20 µm, the distinct striation and the flagellum that does not quite reach body length. The paramylon granules were described by Pringsheim (1942) as „länglich rundlich bis kurz stabförmig (elongate roundish to short rod-shaped)“. In my population the paramylon grains were round or broadly oval.
Fig. 1 a-e: Astasia cylindrica. L = 16–19 µm. Different stages of the metabolic movement of a freely swimming specimen. Note the the cylindrical forms (b and c) during metabolic movement and the distinct striation of the pellicle with counterclockwise spirals (e). Obj. 100 X.