Halteria grandinella: a rapid swimming ciliate with a high frequency of ciliary beating.

A ciliated protozoan, Halteria grandinella, swam backward rapidly with a migration distance per second attaining 100 times the cell size. This high swimming velocity was accompanied by a high frequency of ciliary beating. Recordings with a high-speed digital video (10(3) frames/s) revealed that the frequency during forward and backward swimming was, respectively, 105 +/- 10 Hz and 260 +/- 30 Hz.