Hemidinum nasutum (Stein, 1878)

Most likely ID: n.a.


Synonym: Gloeodinium montanum


Sampling location: Simmelried


Phylogenetic tree: Hemidinium nasutum



  • cells kidney-shaped with rounded poles
  • dorso-ventrally flattened
  • length 22–36 µm
  • cingulum only on left half of cell, tracels along cell in lefthand spiral
  • sulcus reaches posterior end
  • cell wall composed of thin plates, delicate ornamentation
  • chloroplasts numerous, small, yellow-brown to brown, arranged radially
  • eyespot absent
  • nucleus centrally in hypocone
Hemidinium nasutum

I find Hemidinium nasutum from spring to fall in Simmelried in floating plant masses and also in the upper layer of mud. The species is easily identified by a nose-shaped protrusion of the upper half of the cell (epitheca).


Fig. 1 a-c: Hemidinium nasutum. L = 24 µm. A freely swimming specimen in ventral view (a, b) and lateral view from right. Note the nose-shaped protrusion of the epitheca (arrowhead). Obj. 100 X.


Fig. 2 a-c: Hemidinium nasutum. L = 27 µm. Ventral view of a slightly squashed specimen in three focal planes. TF = transverse flagellum lying in the cingulum, LF = longitudinal flagellum. Obj. 100 X.