Maternal and paternal crude oil exposure differentially shapes early developmental transcriptomes and survival outcomes in Atlantic cod (Gadus morhua)

Understanding the long-term biological consequences of crude oil exposure on marine fish is essential for the sustainability of ecologically and economically important species such as Atlantic cod (Gadus morhua). While the direct effects of crude oil on early life stages are well documented, adult reproductive vulnerability and intergenerational consequences remain poorly understood, despite their pivotal role in spawning stock viability. Paternal contributions to next-generation outcomes are particularly underexplored. This study examined how parental exposure to a water-soluble fraction of crude oil affects transcriptomic profiles and survival outcomes in Atlantic cod offspring. Adult fish were exposed for 20 days prior to spawning, and offspring were produced by in vitro cross-fertilization to generate four groups: control (unexposed parents), maternally exposed, paternally exposed and biparentally exposed. Embryos were reared under control conditions, and transcriptome profiles were analyzed from fertilization to hatching, alongside assessments of cardiac function and morphology post-hatch. Offspring from exposed females failed to survive to hatching. Eggs were smaller, and transcriptomic data revealed severe downregulation of genes involved in early developmental processes. Chemical analyses confirmed maternal transfer of a diverse range of petroleum aromatic hydrocarbons to oocytes. Our findings point to disrupted oocyte provisioning, likely linked to endocrine and epigenetic disturbances during oocyte maturation. Paternal exposure had minimal effect on RNA expression, and morphology at hatching. However, reduced survival in early larval stages suggests sublethal effects emerging later, possibly through epigenetic mechanisms, a hypothesis requiring further investigation.