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Journal of Experimental Biology 37,73-82 (1960)
Published by Company of Biologists 1960

The Physiology of Contractile Vacuoles : XI. Effects of Heavy Water on the Water Balance of a Suctorian

J. A. KITCHING ¹, J. E. PADFIELD ¹, and M. H. ROGERS ²

¹ Department of Zoology, University of Bristol
² Department of Mathematics, University of Bristol

1. The suctorian Discophrya collini (Root) has been subjected to D₂O-H₂O mixtures containing up to 99.7% D₂O.

2. In 25% D₂O or over there is a rapid but temporary shrinkage of the body. This shrinkage is difficult to estimate owing to the wrinkling of the body surface, but amounts to at least 10% in the undiluted (99.7%)D₂O.

3. During the period of temporary shrinkage the contractile vacuole ceases activity. Normal activity is resumed when the normal volume is regained. In concentrations of D₂O too low to cause shrinkage there is a temporary fall in the rate of vacuolar output.

4. Return to H₂O leads to a brief but often very considerable rise in vacuolar output.

5. It is concluded that D₂O penetrates less rapidly than H₂O. A difference of at least 10% in the diffusion constants in the membrane would be required to explain our results. We cannot exclude this as unreasonable from our data, although an explanation based on differences in the equilibrium properties of D₂O and H₂O might also be invoked.