Can You Explain The Paramecium Contractile Vacuoles?


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In, Paramecium, unlike Amoeba, there are two contractile vacuoles, occupying somewhat fixed position in the endoplasm, one lying near each end of the body, close to the dorsal surface. These are more elaborate than the single contractile vacuoles of Amoeba for each of then are surrounded by a circlet of 6 to 10 long narrow; spindle shaped radiating canals, extending far into the body cytoplasm.

Each radiating or feeder canal can be differentiated into three parts outer, middle, and inner. Electron microscopy reveals that a spongy network of fine nephridial tubules surrounds the outer or the blind terminal part. The tubules deeply pervaded the surrounding cytoplasm from which they collect the excretory fluid.

The tubules have osmiphilic walls, showing positive staining reaction with somic acid. The whole layer of nephridial cytoplasm surrounding the radiating canals is 1 to 1.5 micron thick. The middle part or ampulla of a radiating canal becomes swollen like a bulb, when filled with the excretory fluid. The accessory vacuoles are, infect, the ampullae's of the feeder canals. The vacuoles in back end pulsates faster than the front side vacuoles because the back region of the body gets ore water due to the presence of cytophyranx.

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