Effects of High Hydrostatic Pressures on the Activity of Flagellates and Ciliates

Abstract

1. The effects of brief exposure to high hydrostatic pressures, ranging in some cases up to 18,000 p.s.i. (1225 atm.) has been studied in various flagellates and ciliates. Closely related species may react very differently. 2. In general high pressure depresses flagellar or ciliary movement, and in most cases, under the standard conditions of the experiments, all movement soon stopped at 8000-14,000 p.s.i. (544-953 atm.). The pressure required to stop movement was usually near that which caused visible structural damage (Table 1, p. 508). Movement was restored on release of pressure provided that the treatment had not been too drastic. 3. In the case of one peritrich ciliate (Epistilis plicatilis) a moderate pressure (1000-3000 p.s.i., or 68-204 atm.) caused an increase of ciliary frequency, but at still higher pressures the frequency was drastically reduced. 4. There is evidence that behaviour was affected by moderate pressures, quite apart from changes in the intrinsic activity of flagella or cilia. Certain flagellates and ciliates were stimulated to activity by application of moderate pressures, and others became motionless. 5. Spirostomum ambiguum was deprived of its ability to reverse or make the avoiding reaction while at high pressure, and at certain pressures the cirri of the hypotrich Stylonychia mytilus beat in a wild and uncontrolled way. It is suggested that high pressure affects ciliary co-ordinating mechanisms in various Protozoa.