Cyclidiopsis acus (Korshikov, 1917)

Most likely ID: n.a.


Synonym: Lepocinclis cyclidiopsis


Sampling location: Purren pond, Simmelried


Phylogenetic tree: Cyclidiopsis acus



  • cells long and slender spindle-shaped
  • not metabolic, rigid
  • length 130–206 µm
  • cells colorless, chloroplasts absent
  • pelliucula spirally striated with very low pitch
  • anterior end snout-like, transversely truncated
  • posterior end acicularly pointed
  • one flagellum, about 35 µm long
  • one eyespot in the height of the reservoir
  • paramylon grains about 25–30 µm long, spindle-shaped with blunt ends
  • nucleus elongated in the middle of the cell
Cyclidiopsis acus

I find Cyclidiopsis acus in the Purren pond and the Simmelried regularly. Sometimes this species occurs in masses, especially in the Simmelried. The species is easily identified by the slender spindle shape and by the absence of chloroplasts (s. figs. 1 a-b and 2). The paramylon grains of Cyclidiopsis acus are also spindle-shaped, with blunted ends (s. fig. 3). In my population I also found specimens containing many small paramylon grains (s. fig. 4) which were irregularly shaped. Possibly these are remnants of degraded, spindle-shaped paramylon grains.


Fig. 1 a-b: Cyclidiopsis acus. L = 194 µm. A freely swimming specimen. CV = contractile vacuole, ES = eyespot, F = flagellum, Nu = nucleus. Obj. 60 X.


Fig. 2: Cyclidiopsis acus. L = 217 µm. A slightly squashed specimen in detail. CV = contractile vacuole, ES = eyespot, F = flagellum, Nu = nucleus, PG = paramylon grains. Obj. 100 X.


Fig. 3: Cyclidiopsis acus. A more transparent specimen with spindle-shaped paramylon grains (PG). The paramylon grains are 31–35 µm long. Note the striated pellicle (SP) of the specimen at the left side. Obj. 60 X


Fig. 4: Cyclidiopsis acus. Two specimens with irregularly shaped, small paramylon grains (SPG). Obj. 60 X