Heliophrya minima
(Rieder, 1936) Foissner, 1988
Most likely ID: n.a.
Synonyms: Heliophrya riederi, Craspedophrya rotunda f. minima
Sampling location: Simmelried
Phylogenetic tree: Heliophrya minima
Diagnosis:
- body discoid, flattened with hayline attachment ring
- no shell or stalk
- diameter 23–50 µm
- about 12 evenly spaced grouped tentacles with globular distal ends
- fully extented tentacles longer than body diameter
- macronucleus discoid in center of the cell
- one spherical micronucleus
- 1–13 contractile vacuoles (on average 5) in periphery of cell
- swarmer lenticular, 19 X 12 µm with 5 equatorial rows of cilia
Heliophrya minima often settles on floating coverslips on samples from the Simmelried. However, I rarely find this suctor.
When Heliophrya minima settles on the floating coverslip, it can be viewed from “below”. This makes the hyaline attachment ring more easily visible by means of which the suctor attaches to the coverslip (s. fig. 1 a). Since Heliophrya minima usually reaches a diameter of only 35 µm and is very flat, one can easily focus through the cell body (s. fig. 1 a-c).
Heliophrya minima can be distinguished from its larger relative Heliophrya rotunda by the evenly spaced tentacles, which are always arranged in bundles in Heliophrya rotunda.
Fig. 1 a-c: Heliophrya minima. D = 36 µm. Three focal planes of sessile specimen attached to the coverslip. Note the hyaline attachment ring (HAR). CV = contractile vacuoles, Ma = macronucleus, Mi = micronucleus, TE = tentacles. Obj. 100 X