Rhabdomonas costata

(Korshikov) Pringsheim, 1942

Most likely ID: n.a.


Synonym: Menoidium costatum


Sampling location: Simmelried


Phylogenetic tree: Rhabdomonas costata



  • cell elongate, bean-shaped
  • anterior end obliquely truncate, posterior end rounded
  • length 20–30 µm
  • periplast with longitudinal ridges, twisted slightly clockwise
  • one flagellum, almost body length
  • spherical nucleus below middle
  • larger paramylon granules often in anterior half
  • sometimes some tiny paramylon grains at posterior end
Rhabdomonas costata

I have so far been able to detect Rhabdomonas costata only in the Simmelried, where the species occurs rather sporadically. It is easy to distinguish the species from Menoidium or Astasia, because the cell is not flattened (like Menoidium), has distinct longitudinal ridges and is not metabolic (like Astasia). For Rhabdomonas costata a slender, slightly curved shape is typical. The cell is transversely truncated at the anterior end.


More images and information of Rhabdomonas costata: Michael Plewka-Freshwater life-Rhabdomonas costata


Fig. 1 a-e: Rhabdomonas costata. L = 29 µm. Different focal planes of a freely swimming specimen. Note the longitudinal ridges (LR) of the pellicle. F = flagellum, Nu = nucleus. Obj. 100 X.


Fig. 2 a-c: Rhabdomonas costata. L = 28 µm. Different focal planes of a second freely swimming specimen. Obj. 100 X.