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. These frequencies are the highest among cilia and flagella reported to date. Electron microscopic observation of the ciliary structure confirmed normal 9 + 2 arrangements of the axoneme except that cilia for migration are bundled into membranelles. Ciliary beating of saponin-treated cells was reactivated by the addition of Mg2+ -ATP, although the beating amplitude was smaller than that of intact cells. Kinetic analysis of the ATP-dependent increase of beating frequency revealed that the maximal frequency in the presence of free Ca2+ and 0.9 microM Ca2+ was approximately 60 and 110 Hz, respectively. A possible mechanism to increase beating frequency with Ca2+ is discussed. Copyright 2005 Wiley-Liss, Inc.