Social stress in Zebrafish sperm. Social stress in fathers affects sperm small RNA and offspring transcriptome profiles

Environmental changes may affect paternal condition and following generations but the underlying transmission mechanisms of such information is unknown. Male-male competition induces a physiological stress response and affects male hormone levels, ejaculate traits and hatching rates in their offspring. Here we investigated the potential role of small RNAs in sperm in the transmission of male condition to the next generation. We exposed male zebrafish Danio rerio to high and low male-male competition environments for two weeks and collected sperm samples at the end. We also performed IVFs using a split-clutch design to distinguish between paternal and maternal effects and collected embryos at 24 hours to test for differentially expressed genes at this key developmental stage. We sequenced mi- and piRNAs and the full transcriptome in the resulting offspring and ran a differential expression analyses. We identified differentially expressed sperm mi- and piRNAs, with the strongest effects observed in sperm of males switching from a high to a low competition environment. We identified 612 differentially expressed genes in the embryos. The changes in gene expression in the embryos support the idea of faster development and hatching, and can be linked to some of the differentially expressed small RNAs in sperm.