FIG. 4.

Arrangement of sperm bundle inside the PSR. A–D) Still images of fast-frozen, wild-type sperm that entered the PSR. The uterus is positioned on the right beyond the view, and the DSR is on the left. A) This PSR is filled with sperm, with heads visible along the length (arrowheads). B) An enlarged image of A shows intertwining sperm flagellar bundles that are mostly parallel to each other. A small number of bent flagellar loops (arrows) are present in the mix. C) The sperm heads in the bundle are either well separated or clustered with a separation spacing of less than one head length (big arrowhead). D) Some clusters (arrowheads) contain as many as 22 sperm. E) The number of heads found in a cluster (x-axis) and observed frequency (y-axis) are plotted (n = 164 heads). Bar = 0.1 mm.