Petalomonas steinii (Klebs, 1893)

Most likely ID: n.a.


Synonym: n.a.


Sampling location: Simmelried


Phylogenetic tree: Petalomonas steinii



  • length 38 – 42 µm, width 22- 36 µm, thickness 10 – 16 µm
  • body ovoid to triangular
  • dorso-ventrally flattened
  • one flagellum
  • one dorsal keel
  • triangular in cross section
  • periplast with delicate lingitudinal striation
  • ventral side flat or concave
Petalomonas steinii

I found this specimen of Petalomonas steinii in 2008 in Simmelried. The specimen is 70 µm long and 45 µm wide. Thus it is much larger than given by Lemmermann (L 35 – 42 X W 22 µm) and Skuja (L 27-36 X W 12 -22 µm). Nevertheless I believe that Petalomonas steinii is present here. This I conclude from the presence of only one flagellum, the keel which runs dorsally and the rounded, triangular shape, which was described as a shape variant by Klebs (see drawing d, after Klebs). The species Petalomonas steinii is generally described as “strongly varying”. In addition, there is no convincing alternative.


Fig. 1 a-d: Petalomonas steinii. L = 70 µm. Ventral view of a slightly squashed specimen. The keel (K) on the dorsal side is only blurred (due to focussing through the cell). CV = contractile vacuole, F = flagellum, NU = nucleus. 100 X.