Abstract

Optical tweezers are used in Paramecium to control the positions of nuclei that play an important role during sexual reorganization. The beam from a Nd:YAG laser (λ = 1060 nm) was directed through a beam expanding telescope, through the microscope, and onto the specimen. With a 100× planachromatic phase contrast objective, ~100 mW could be focused into a 2-3-μm spot. First, the living Paramecium was immobilized in a rotocompressor. As the result of radiation pressure at the diffraction-limited focus of the laser beam, organelles in these immobilized Paramecium could be easily trapped and manipulated. The structures that could be most easily trapped and moved were the crystals. On the other hand, with available power levels we were not able to directly trap the micro- and macronuclei because of their small relative index of refraction. However, trapped crystals could be moved virtually anywhere in the cell at the observer’s discretion, and it was demonstrated that they could be used to push the micronuclei around the cell at will. Moreover, the growth and reproduction of Paramecia that had undergone laser irradiation at our available power levels showed no deleterious effects and showed no differences with non-irradiated control specimens.

© 1991 Optical Society of America