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 multiformis was collected in freshwater ponds near Konstanz, Germany. Stentor multiformis is blue-ish. The pigment granules are arranged in longitudinal stripes in the cortex. Depending on the habitat the colour can be more or less intense or greenish blue. The macronucleus of this species is spherical. Focal plane on the spherical macronucleus is the bright regiuon in the middle of the cell form. This picture was taken by Martin Kreutz using an Olympus microscope. Image copyright: Martin Kreutz, image used under license to MBL (micro*scope).
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From the collection
Freshwater ponds of Konstanz (Germany)
|Description of Stentor multiformis: Heterotrich ciliate, 200-500 micrometres long (usually 250 micrometres). With zoochlorellae. Cortical granules azure to sea green, appears blue or blue-green in transmitted light. Trumpet-shaped when extended; conical or clavate in contraction. Macronucleus oval. Widespread. Freshwater, marine and terrestrial.