LAUSR

BACKGROUND Interactions between sperm and the female reproductive tract (FRT) are complex, in many cases poorly understood, and likely to contribute to the mechanistic basis of idiopathic infertility. As such, it is not surprising that the FRT was often viewed historically as a "hostile" environment for sperm. The FRT has also been touted as a selective environment to ensure that only the highest quality sperm progress to the oocyte for the opportunity to participate in fertilization. Recent advances, however, are giving rise to a far more nuanced view in which supportive sperm x FRT interactions - in both directions - contribute to beneficial, even essential, effects on fertility. In this perspective article, we discuss several examples of positive sperm x FRT interactions. We believe that these examples, arising in part from studies of taxonomically diverse, non-mammalian systems, are useful to efforts to study mammalian sperm x FRT interactions and their relevance to fertility and the advancement of assisted reproductive technologies. This article is protected by copyright. All rights reserved.