Laser light-scattering studies of bull spermatozoa. I. Orientational effects.

Calculations based on the known dimensions of bull spermatozoa show that the scattered light intensity is strongly dependent upon the relative orientation of the particle to the incident beam. The magnitude of this effect of apparently much greater than for other systems where motility has been investigated by dynamic light scattering. The calculations show that the scattering source can be approximated by a small spinning mirror, and consequently the greatest light intensity at the detector results from cells swimming in a direction perpendicular to the scattering vector. The calculations are in substantial agreement with photographic observations, as well as direct measurements of the scattered intensity. Previous treatments of dynamic light scattering from swimming bull spermatozoa based on point scattering models are shown to be incorrect.