Motile components in early rat spermatids.

In early rat spermatids, two distinctly different kinds of movements of cell components were detected by video-analysis. The primary flagellum, a typical 9 + 2 axonema, is capable of inducing wave-like movements in three dimensions, unlike late spermatid forms, which display motility of the now thickened flagellum only by repeated bending of its extreme part. Additionally, at the apical regions of spermatids of the same early stage, cytoplasmic protrusions executed rhythmic movements at a frequency of almost three times per second. The two kinds of motility of the different components in the same type are thought to be involved in normal orientation and transfer of spermatids in the tubulus seminiferous during their differentiation to sperm.