Tetrahymena: effect of freezing and subsequent thawing on breeding performance.

Tetrahymena pyriformis, syngen 1, frozen in 10 percent dimethyl sulfoxide, stored for 2 months, and then thawed could conjugate normally. More significantly, they were viable, in normal numbers, through two sex ual reorganizations. The strains ap parently did not sustain genetic dam age during the treatment. The tech niques offer considerable promise for the maintenance of breeding stocks in ciliated protozoans.