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1 February 2003 Effect of Preillumination on Photomotile Responses of the Marine Ciliate Fabrea salina
Roberto Marangoni, Giuliano Colombetti
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Fabrea salina is a marine ciliate that shows photomotile responses such as positive phototaxis and a step-down photophobic reaction. We found that preilluminated F. salina cells show a phototactic response significantly greater than that of dark-adapted cells when exposed to the same phototactic light stimulus. In particular, positive phototaxis is strongly enhanced by preillumination. This enhancement effect depends on the preillumination light irradiance, on the total preillumination dose, and on the duration of the dark interval between preillumination and the phototaxis measurement. Our results show that the determining factor is the total preillumination dose given to the sample. The enhancement effect shows an asymptotic behavior over a certain range of energy values (10–200 W/m). Further, the effect is transient; after 120 s in the dark, the cells lose any memory of the preillumination, independent of the preillumination energy received. These results are tentatively discussed in terms of light-driven membrane potential or membrane channel conductances.

Roberto Marangoni and Giuliano Colombetti "Effect of Preillumination on Photomotile Responses of the Marine Ciliate Fabrea salina," Photochemistry and Photobiology 77(2), 204-209, (1 February 2003).<0204:EOPOPR>2.0.CO;2
Received: 13 August 2002; Accepted: 1 November 2002; Published: 1 February 2003

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