Alternating torsions in a living '9+2' flagellum

Live spermatozoa of the Japanese quail were observed as they swam in highly viscous salines. Under these conditions, torsions of the flagellum were re adily seen. The torsions had a characteristic magnitude (nominally 180 degr ees) and pattern of incidence. As a cycle of bending propagated over it, ea ch position on the flagellum experienced first a sinistral torsion and, lat er, a restoring dextral torsion. The two zones of torsion were each associa ted with bending; between them was a torsion-free zone that tended to be st raight. The amount of interdoublet sliding needed to generate the torsions may be as little as 10 nm. These dynamic propagating torsions have been det ected by following the angular displacements of individual (swollen) mitoch ondria lying adjacent to the axoneme. It is suggested that torque generatio n is a primary outcome when the unconstrained '9 + 2' axoneme is activated.