To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video Movie 2 Frame from a microscopic video of Prss50 null sperm at 40X magnification demonstrating a sperm with two heads (blue circle; 0.1x speed) as well as conjoined sperm. PRSS50 is a testis protease responsible for proper sperm tail formation and function Jason M. Scovell, Juan C. Bournat, Adam T. Szafran, Minerva Solis, Joshua Moore, Armando Rivera, Ching H. Chen, Jason Zhang, Nathan Wilken, Abhishek Seth, and Carolina J. Jorgez Development 2021. 148:None-None; doi: 10.1242/dev.197558 Download Original Video