Reproductive fluids enabling cryptic female choice of paternity do not induce concomitant gamete-mediated paternal effects in embryos of hybridizing salmonid fishes

Abstract

Post-mating sexual selection in the form of cryptic female choice provides opportunities for females to bias paternity to favor preferred males. However, little is known regarding how cryptic female choice might affect offspring outside of paternity, via female modified changes to sperm environmental experience. Gamete-mediated paternal effects are widespread, and female alteration of sperm experience may play an unrecognized role in shaping cryptic female choice. Using hybridizing salmonid fishes that have documented female mediated conspecific sperm preference via differential upregulation of sperm swimming performance, we created artificial split-brood and split-ejaculate fertilizations to determine if sperm experience in different conditions influences offspring development. Prior to contact with eggs, sperm experienced 20s of swimming in either water, or water with the addition of conspecific ovarian fluid or heterospecific ovarian fluid. Over 186 days, we quantified hatch timing, hatchling size, and developmental stage and found that differential sperm experience created biologically irrelevant (average effect size of 1.06%) changes on offspring development, which were much smaller than the effects of hybridization itself (average effect size of 10.45% for the species of the father). Since ovarian fluid drastically changes sperm experience when compared to water, we conclude that females can use ovarian fluid to bias paternity without concomitant consequences to offspring development.