Some sperm cells poison their competitors

Competition among sperm cells is fierce - they all want to reach the egg cell first to fertilize it. A research team now shows in mice that the ability of sperm to move progressively depends on the protein RAC1. Optimal amounts of active protein improve the competitiveness of individual sperm, whereas aberrant activity can cause male infertility.

source https://www.sciencedaily.com/releases/2021/02/210204144021.htm