Phacus acuminatus (A. Stokes, 1885)

Most likely ID: n.a.


Synonym: Phacus acuminata


Sampling location: Simmelried, Purren pond, Mainau pond, Ulmisried


Phylogenetic tree: Phacus acuminatus



  • cell broadly ovoid, strongly flattened
  • length 23–40 µm, width 20–30 µm
  • often 1–2 prominent paramylon bodies
  • many chloroplasts, disc-shaped
  • very short caudal spine, V-shaped
  • one flagellum, about body length
  • striation of the pellicle longitudinally
Phacus acuminatus

Phacus acuminatus can is a very common species and I find it in different sites. The species can be recognized by its broad oval shape and the very short, V-shaped spine (s. fig. 1b). Usually 1–2 large, disc-shaped paramylon bodies are present in the cell, sometimes with a central hole or even ring-shaped. The specimens in my population were mostly 30 µm long. Because of the small size the species is often overlooked.


Fig. 1 a-c: Phaus acuminatus. L = 30 µm. Different focal planes of a slightly squashed specimen. CS = caudal spine, ES = eyespot, F = flagellum, Nu = nucleus, PP = prominent paramylon body, SP = striation of pellicle. Obj. 100 X.


Fig. 2: Phaus acuminatus. L = 32 µm. A second, strongly squashed specimen with two prominent paramylon bodies (PP). Chl = disc-shaped chloroplasts. Obj. 100 X.