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Effect of Preillumination on Photomotile Responses of the Marine Ciliate Fabrea salina ¶
Author(s) -
Marangoni Roberto,
Colombetti Giuliano
Publication year - 2003
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2003)0770204eopopr2.0.co2
Subject(s) - phototaxis , ciliate , biology , biophysics , botany , ecology
ABSTRACT 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.