Parental stressor exposure simultaneously conveys both adaptive and maladaptive larval phenotypes through epigenetic inheritance in the zebrafish (Danio rerio)

Genomic modifications occur slowly across generations, whereas short-term epigenetic inheritance of adaptive phenotypes may be immediately beneficial to large numbers of individuals, acting as a bridge for survival when adverse environments occur. In the present study, crude oil was used as an example of an environmental stressor. Adult zebrafish (P-0) were dietarily exposed for 3 weeks to no, low, medium or high concentrations of crude oil. The F-1 offspring obtained from the P-0 groups were then assessed for transgenerational epigenetic transfer of oil-induced phenotypes. The exposure did not alter body length, body and organ mass or condition factor in the P-0 groups. However, the P-0 fecundity of both sexes decreased in proportion to the amount of oil fed. The F-1 larvae from each P-0 were then exposed from 3 hpf to 5 dpf to oil in their ambient water. Remarkably, F-1 larvae derived from oil-exposed parents, when reared in oiled water, showed a 30% enhanced survival compared with controls (P<0.001). Unexpectedly, from day 3 to 5 of exposure, F-1 larvae from oil-exposed parents showed poorer survival in clean water (up to 55% decreased survival). Additionally, parental oil exposure induced bradycardia (presumably maladaptive) in F-1 larvae in both clean and oiled water. We conclude that epigenetic transgenerational inheritance can lead to an immediate and simultaneous inheritance of both beneficial and maladaptive traits in a large proportion of the F-1 larvae. The adaptive responses may help fish populations survive when facing transient environmental stressors.