The action of low-intensity light on biological objects has been studied by estimating the mobility variation of the ciliate Paramecium caudatum Erhenberg, 1838. Using apparatus that makes it possible to measure the motion of the paramecia after they are irradiated by laser diodes (irradiation wavelength at 445, 662, and 808 nm) and by an LED (518 nm), speed variations were observed immediately after irradiation, having a strongly expressed oscillatory component, which is presumably explained by the action of self-regulation mechanisms. In the days following irradiation with energy density 1 J/cm(2) in the blue-green region, the speed of the ciliates increases by about a factor of 1.3 by comparison with a control experiment (with no irradiation). The mobility gradually decreases as the energy density of the irradiation increases, falling by a factor of 1.26 at 15 J/cm(2) (445 nm) and by a factor of 1.19 (518 nm). Irradiation with wavelength 662 nm has a similar effect, except that the stimulating effect is appreciably stronger (by a factor of 1.64 at 1 J/cm(2)) while the suppression effect by a factor of 1.23 at 15 J/cm(2) is maintained. As far as the near-IR region is concerned (808 nm), the stimulation effect is present at all doses, demonstrating the greatest growth by a factor of 1.68 when the energy density is 15 J/cm(2). (C) 2021 Optical Society of America
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