portrait

Description :

Stentor (sten-torr) is a genus of large, trumpet-shaped ciliates, commonly found in freshwater ponds, usually attached with the posterior end to vegetation or other surfaces. Detached individuals may swim freely and adopt an oval to pyriform shape. At the anterior end of the cells a conspicuous peristomial field with a system of adoral membranelles spiralling clockwise to the cytostome. The cilia of the membranelles are much longer than the somatic cilia. The macronuclei of Stentor may be spherical, elongate to a long strand or formed like a string of pearls. There is a single contractile vacuole with two collecting canals near the cytostome. Some species build transparent loricas of secreted mucus. The cells can be intensive coloured by pigmentation granules located in the pellicula (green, pink, blue, orange or violet). This specimen of Stentor roeselii was collected in freshwater ponds near Konstanz, Germany. Stentor roeselii is colourless and the macronucleus is band-shaped. This specimen built up a pyriform lorica covered with foreign bodies. Bright field.