Stentor roeselii (Ehrenberg, 1835)
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Pond of the convent Hegne, Simmelried
Phylogenetic tree: Stentor roeselii
Diagnosis:
body elongated trumpet-shaped, contracted ellipsoid to club-shaped
appears yellowish or brownish, no symbiotic algae
length 500–1200 µm, sometimes up to 3000 µm (of elongated specimens)
adoral membranelle running in clockwise to oral funnel
attached with thigmotactic cilia to the substrate
sometimes in a hyaline case, 200–300 µm long
macronucleus vermiform, along longitudinal axis of cell
7–20 spherical micronuclei adjacent to the macronucleus
contractile vacuole on left wall of oral funnel with one collecting duct reaching posteriorly
At low magnification, Stentor roeselii resembles Stentor muelleri, which also appears yellowish or brownish. However, Stentor roeselii is about 30 % smaller than Stentor muelleri and appears somewhat plumper when fully elongated (s. fig. 1 c). The decisive distinguishing feature, however, is the shape of the macronucleus. In Stentor roesilii it is vermiform shaped, whereas in Stentor muelleri it is monoliform and resembles a pearl necklace. The shape of the macronucleus can be easily recognized even in slightly squashed specimens (s. figs. 2 and 3 b). In contrast, the small micronuclei, which are attached to the macronucleus, can only be recognized in strongly squashed specimens (s. fig. 5).
Fig. 1 a-c: Stentor roeselii. L = 710 µm (of elongated specimen). A contracted (a) and fully elongated specimen in brightfield illumination. Obj. 20 X.
Fig. 2: Stentor roeselii. L = 710 µm. The same specimen as shown in fig. 1 a-c in DIC. Obj. 20 X.
Fig. 3: Stentor roeselii. L = 730 µm. A slightly squashed specimen. Note the vermiform macronucleus (Ma) arranged longitudinally in the cell. Obj. 40 X.
Fig. 4 a-b: Stentor roeselii. Focal plane on the pellicle with striation of colorless granules (a) and on the vermiform macronucleus (b, Ma) in a slightly squashed specimen. Obj. 60 X.
Fig. 5: Stentor roeselii. The vermiform macronucleus (Ma) in a strongly squashed specimen. Two micronuclei (Mi) are in the focal plane. Obj. 100 X.