Vorticellae Light Microscopy

Written by microscopes

Saturday, 04 August 2007

Vorticellae and Light Microscopy.

Vorticellae and Light Microscopy

Another interesting group of Infusoria are the Vorticellae. There are about seventy species known, but we will describe only one, since the microscopist will have no difficulty in recognizing the genus once he has seen one member. They belong to the class of fixed Infusoria, are very common, scarcely a leaf or twig of any aquatic plant being without at least one of them, and most of them are colorless, or nearly so. Green ones do occur, Vorticella smaragdina being one example, but most of them are entirely devoid of color. Individuals are invisible to the naked eye, but magnifications of Xs5O will reveal them clearly. The body is somewhat bell shaped and is carried at the apex of a contractile stem. The front or rim is wreathed with cilia, for the same purpose as was explained in connection with Carchesium.

While individual Vorticellae are invisible, their multiplication in colonial groups is sometimes so rapid during the summer that the entire colony breaks away from its mooring and goes floating away. These groups look like small spots of saliva or mucus floating on the water or attached to the leaves and stems of plants. When such a spot is discovered and touched with a needle-point, it seems to grow smaller or disappear almost entirely. Pick the plant on which it is found and place it in water for later examination.

Do not be alarmed if, upon reaching home, your colony seems to have vanished. Place the plant in an aquarium and await developments. It will presently appear and afford many hours of study. These Infusoria can contract with a suddenness that is most disconcerting. The observer may be calmly examining a Vorticella under the microscope when, for no apparent reason, it disappears like a flash, and one feels that the slide has been moved. Soon, however, it may be seen separating itself from its support, the coiled stem growing longer and straighter, until the whole animal is again in view. Sometimes it is barely extended when it again leaps from sight. If the student has an aquarium he will do well to introduce several colonies of these interesting animals, for they are always worth studying.