Osmoregulation in Paramecium.
| Many single celled organisms use a combination of techniques for maintaining osmotic balance. Paramecium caudatum is a good example. Paramecium typically lives in a hypotonic environment which means that water diffuses from the outside to the inside of the animal by osmosis. Paramecium removes water by using active transport and has a pair of organelles just for this purpose. These organelles are called contractile vacuoles. When Paramecia are examined using the light microscope the contractile vacuoles can be seen as a pair of spherical structures surrounded by a series of radiating ducts. These ducts collect water and pump it into the central area by means of sets of contractile fibers. In turn, the central sphere contracts when it is full, forcing water to the outside of the protist. | |
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In addition, Paramecium and other Protista have a second technique for regulating osmotic balance. If Paramecium is examined under polarized light, bright "inclusions" are typically visible as in the picture show here. These are crystals of salts. If the cytoplasm becomes excessively dilute, then the organism can release salts from these crystals to make the cytoplasm more hypersonic. Conversely if the cytoplasm becomes excessively hypersonic, salts can be taken out of solution by the organism. |
Both copyright Ralf Schmode. Used with permission 1998
schmode@vossnet.de
pgd revised 2/17/01