Stroboscopic illumination for the assessment of hyperactivated motility of mouse spermatozoa

Spermatozoa showing hyperactivated motility can be recognized in multiple-exposure micrographs. The cells were confined in 10-micrometer-deep chambers, illuminated in darkfield conditions, and photographed using a stroboscope (10 Hz). Hyperactivation, as judged from the pattern of ten superimposed images, could be promoted by raising the ionic strength of the medium but did not occur in the absence of calcium.