Does post-ejaculatory sperm experience prior to fertilization alter embryo performance beyond paternity in an external fertilizing fish?

Abstract Beyond direct genetic inheritance, parents can influence the phenotype of their offspring by other means. Those based on experiences of the mother (maternal effect) and the father (paternal effect) prior to mating are well documented. Additionally, recent research has suggested that the environment encountered by sperm post-ejaculation might impact offspring development beyond the transfer of the paternal genome. However, the underlying mechanisms are generally not clear, and available literature presents conflicting perspectives on whether such effects are adaptive (anticipatory paternal effect) or maladaptive. Capelin (Mallotus villosus) sperm and embryos are sensitive to salinity and might represent a good system in which to investigate these discrepancies. We used a split-ejaculate and split-brood experimental block design to expose capelin sperm to known benign (25 psu) and stressful (35 psu) salinity prior to egg contact, and we split each batch of fertilized eggs for incubation at matched and mismatched salinity to those of sperm exposure. Our findings revealed no differences in hatch characteristics between embryos produced by sperm exposed to benign and stressful salinity conditions. A follow-up experiment found the same result with an increased selection gradient consisting of 5 and 35 psu. Our study does not support the hypothesis that sperm experiences exert an influence on the development of offspring characteristics.