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The contractile vacuole complex (CVC) is an organelle composed of
several parts that is found mostly in protistans but also in some
lower forms of life such as fresh water sponges and the zoospores of
some fungi. Once thought to be principally involved in osmoregulation
it is now known to be involved also in the regulation of calcium, at
least in some cells such as Dictyostelium and
Paramecium, as the calcium concentration of the CV in
Paramecium increases dramatically when the cell is placed in a
high calcium-containing environment In Paramecium multimicronucleatum the contractile vacuole (CV) when filled consists of a single membrane-lined vacuole containing water and ions such as potassium, sodium, calcium and chloride. A flocculent material is sometimes seen that varies according to the growth medium and seems to result, at least in part, from some backflow into the CV when the CV is open to the cell’s environment. The CV in Paramecium, unlike Amoeba, is not free to move about in the cytosol but is bound to a permanent CV “pore” by ribbons of microtubules that arise from the edge of the pore. As there are usually two CVCs per cell there are two pores on the dorsal surface of the cell, one in the anterior and one in the posterior half of the cell. EM taken on 3/8/80 by R. Allen with Hitachi HU11A TEM. Neg. 5,000X. Bar = 1µm. Published in J. Protozool. 35:63-71, 1988. |
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