Orientation of Paramecium swimming in a DC magnetic field

Abstract

We found that a ciliated protozoan, Paramecium, swam perpendicular to a static (DC) magnetic field (0.68 T). The swimming orientation was similar even when the ionic current through the cell membrane disappeared after saponin treatment. To determine the diamagnetic anisotropy of intracellular organs, macronuclei, cilia, and secretory vesicles, trichocysts, were selectively isolated. Both cilia and trichocysts tended to align their long axis parallel to the magnetic field (0.78 T). Paramecium mutants that lack trichocysts also swam perpendicular to the magnetic field, although the proportion fraction was smaller than the normal population. Since large numbers of cilia and trichocysts are arranged at right angles to the long axis of the cell, the diamagnetic anisotropies of cilia and trichocysts cause the long axis of the cell to align perpendicular to the magnetic field. In contrast to the DC magnetic field, an alternative (AC) magnetic field (60 Hz, 0.65 T) had almost no effect on the swimming orientation of Paramecium.

Impact of a High Magnetic Field on the Orientation of Gravitactic Unicellular Organisms—A Critical Consideration about the Application of Magnetic Fields to Mimic Functional Weightlessness

“…Parallel swimming of P. caudatum with respect to the direction of the applied strong magnetic field (*3 T) (Fujiwara et al, 2006;Valles, 2006a, 2006b), as well as perpendicular swimming of P. aurelia to a static magnetic field of moderate intensity (0.68 T) (Nakaoka et al, 2002), has been observed. Tanimoto et al (2002) described magnetotaxis of E. gracilis in a horizontal magnetic field gradient.…”

“…In a previous study, this group also investigated isolated cell organelles with respect to their diamagnetic anisotropy and thus orientation within a static magnetic field of 0.78 T; cilia as well as trichocyts oriented in parallel, while isolated macronuclei showed no tendency to align. Thus, orientation is determined by the diamagnetic anisotropy of the cell organelles (Nakaoka et al, 2002).…”

Effects of a 50 Hz magnetic field onDictyostelium discoideum (Protista)

“…However, it has been observed that magnetic fields affect swimming behavior of different species of Ciliates. The movement pattern appears to be altered both by ELF-EMFs (50 Hz, 0.5-2 mT; 60 Hz, 0.6 T) [Hemmersbach et al, 1997;Nakaoka et al, 2000] and static magnetic fields (0.126 T, 0.68 T) [Rosen and Rosen, 1990;Nakaoka et al, 2002]. Studies on cell population growth have revealed significant decreases in the growth rate of Amoeba hatchetti, A. castellanii, and A. polyphaga exposed to a uniform static magnetic field (71 or 106.5 mT) [Berk et al, 1997], as well as of Physarum polycephalum exposed to a 75 Hz magnetic field [Marron et al, 1975;Greenebaum et al, 1982]; conversely, a 72 Hz EMF increased cell fission rate in Paramecium [Dihel et al, 1985].…”

Effects of static magnetic fields on growth ofParamecium caudatum

“…Taking into account the above molecular behaviors, Paramecium, which is constituted of these heterogeneously organized diamagnetic substances, would be expected to undergo magnetic orientation. Such an approach has already been investigated by Nakaoka et al [2002], whereby K þ -hyperpolarized Paramecium cells exposed to a 0.68 T static DC field were found to orient themselves perpendicular to the magnetic field within a few seconds of exposure. The constant effort applied to escape from the influence of the magnetic force, which is directed perpendicularly to the direction of the field and direction of the motion, could increase the stress load of the organism due to the high-energy demand of the process.…”

“…The effects of magnetic fields on swimming behavior of Paramecium have been studied previously [Rosen and Rosen, 1990;Nakaoka et al, 2002]. Changes in swimming activities are related to the structure of the Paramecium cortex.…”