These are time-lapse videos of Caenorhabditis hermaphrodites that were (A) mated with the same species and (B) mated with a different species. Male sperm were fluorescently labeled and appear as white dots. In A, sperm localize normally to the spermatheca and uterus (outlined in yellow) and in B, sperm migrate abnormally outside of the gonad (outlined in white). Scale bar represents 100 microns. Images were taken every 10 seconds and the video is sped up 10X.