EFFECTS OF Ca++ AND K+ ON MOTILITY AND PHOTOMOTILITY OF THE MARINE
CILIATE FABREA SALINA
Spartaco Puntoni, Roberto Marangoni,
Domenico Gioffrè and Giuliano Colombetti
Istituto di Biofisica del C.N.R., Via S. Lorenzo
26, 56127 Pisa, Italy
Abstract
Fabrea salina is a motile ciliate marine protozoan belonging to the order
Heterotrichida, that shows photomotile reactions. We report here the results of a study on
motility and phototaxis of F. salina exposed to different Ca++ and K+ concentrations. Our
findings show that concentrations of potassium ions greater than that of the growth medium
and concentrations of calcium ions lower than that of the growth medium cause a
significant increase in phototactic response, while the cell speed is not significantly
affected. A more thorough analysis shows that the absolute concentrations of Ca++ or K+
are not important and that the phototactic responsiveness depends mainly on the ratio of
the K+ concentration to the square root of the Ca++ (the so called Ja value), in agreement
with the results obtained in other protozoa. Our results are tentatively discussed in
terms of altered membrane potential or ion channel conductances.
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