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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3918

Ochiai Tsutomu, Asai Hiroshi, and Fukui Keiji; Hysteresis of Contraction-Extension Cycle of Glycerinated Vorticella. J.Protozool. 26(3):420-425, 1979

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The helical coiling state of a glycerinated stalk in the family Vorticellidae had been regarded, without any evidence, as a reversible and completely equilibrated mechano-chemical system regulated by the external free Ca2+ concentration. Our present detailed observations of many individual stalks of glycerinated Vorticella convallaria revealed that the contraction-extension cycle of the helical stalks caused by increasing and decreasing free Ca2+ concentration in the medium represents a kind of hysteresis. This phenomenon was observed in extensively glycerinated Vorticella in a medium of very low or physiological ionic strength, as well as in briefly glycerinated ciliates. With regard to the configurational change in various parts of a glycerinated stalk during the contraction-extension cycle, it was found that the initial bending of the stalk caused by increasing free Ca2+ concentration begins to take place near the zooid (head) while the initial reextension of the stalk with decreasing free Ca2+ concentration takes place simultaneously throughout the entire stalk. The Ca2+ threshold of complete reextension of the part of the stalk near the rootlet was found to be much higher than that near the zooid.