ABSTRACT
Sperm cells are unusual in spending a crucial part of their life cycle traveling as “free-living” cells in the female reproductive tract, where conditions are fundamentally different from those inside the body. For example, sperm face O2 deprivation and uctuations of pH that would kill many cells. In addition, during the long transit to the egg, sperm face uncertain levels of energy substrates and variable levels of cations, essential for their excitatory nature. It is now clear that sperm have adapted to their free-living environment both biochemically and structurally. Specically, sperm appear to have evolved DHA membranes as an adaptation to the free-living state, allowing them to successfully traverse the hostile environment of the female reproductive tract. Interestingly, considering the roles of DHA membranes of sperm from an ecological perspective has helped illuminate in molecular terms why sperm tail membranes are enriched with DHA and why this adaptation is essential in the human reproductive cycle.
