Short-term variation in sperm competition causes sperm-mediated epigenetic effects on early offspring performance in the zebrafish

Abstract

The inheritance of non-genetic factors is increasingly seen to play a major role in ecology and evolution. While the causes and consequences of epigenetic effects transmitted from the mother to the offspring have received ample attention, much less is known about how variation in the condition of the father affects the offspring. Here, we manipulated the intensity of sperm competition experienced by male zebrafish Danio rerio to investigate the potential for sperm-mediated epigenetic effects over a relatively short period of time. We found that the rapid responses of males to varying intensity of sperm competition not only affected sperm traits as shown previously, but also the performance of the resulting offspring. We observed that males exposed to high intensity of sperm competition produced faster swimming and more motile sperm, and sired offspring that hatched over a narrower time frame but exhibited a lower survival rate than males exposed to low intensity of sperm competition. Our results provide striking evidence for short-term paternal effects and the possible fitness consequences of such sperm-mediated non-genetic factors not only for the resulting offspring but also for the female.

Keywords: Danio rerio; epigenetic inheritance; larval hatching; offspring survival; paternal effects; social environment.

Figure 1.

The change of sperm velocity over time (seconds post-activation), showing means and 95% CI. (a) VCL: curvilinear velocity (μm s⁻¹), (b) VSL: straight-line velocity (μm s⁻¹); (c) VAP: average path velocity (μm s⁻¹). In all three panels, the full line and black dots represent the ‘high’ sperm competition treatment, whereas the ‘low’ sperm competition treatment is represented by the dotted lines and open squares.

Figure 2.

Differences in hatching timing (in hours since fertilization) between offspring sired by males from high (solid line) and low (dashed line) sperm competition environments as shown by curves of hatching success. Shown are the proportions of hatched offspring in the two treatments measured in 2-h intervals between 48 and 80 h post-fertilization.