Stentor muelleri (Ehrenberg, 1831)

Most likely ID: n.a.


Synonym: n.a.


Sampling location: Ulmisried, Purren pond, Mainau pond, Bussenried, Bündtlisried, Pond of the waste disposal company Constance, Simmelried


Phylogenetic tree: Stentor muelleri



  • body elongated trumpet-shaped, contracted obovoid to club-shaped

  • appears yellowish or brownish, no symbiotic algae

  • length 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

  • macronucleus moniliform of about 10–20 spherical parts

  • 10–17 spherical micronuclei adjacent to the nodules of the macronucleus

  • contractile vacuole on left wall of oral funnel

Stentor muelleri

Stentor muelleri is one of the most common ciliates. I find it in practically all my sampling sites. It is easily recognizable by its mostly yellow-brown color and the moniliform macronucleus, which can be seen even in unsquashed specimens (s. fig. 4). The two other Stentor species with a moniliform macronucleus are Stentor coeruleus (colored blue or blue-green) and Stentor polymorphus (green due to symbiotic algae).


If a few specimens of Stentor muelleri are placed under a coverslip with a high layer thickness, they stretch out completely after a short time at most. The specimens in my population were between 1000 – 1600 µm long when fully elongated.


Fig. 1: Stentor muelleri. L = 1100–1350 µm. Some specimen settled in a detritus flake. Obj. 4 X.


Fig. 2 a-b: Stentor muelleri. L = 1450–1560 µm. Two fully elongated specimens. Note the hyaline case (HC) of the specimens, only visible by attached particles and algae. Obj. 10 X.


Fig. 3 a-b: Stentor muelleri. L = 1060 µm. A further specimen in a hyaline case (HC) visible by attached bacteria. Obj. 10 X.


Fig. 4: Stentor muelleri. L = 1060 µm. The anterior half of the specimen as shown in fig. 3 a-b. Note the nodules of the moniliform macronucleus. Obj. 20 X.


Fig. 5: Stentor muelleri. The nodules of the moniliform macronucleus (Ma) with the adjacent micronuclei (Mi) in a strongly squashed specimen. Obj. 100 X.