Introduction
The Atlantic salmon industry is challenged by large losses at sea, especially during the first months after the transfer from freshwater to seawater, which is often attributed to a poor smoltification status of the fish. Although a vast array of research is currently directed towards the understanding of the process of smoltification, alternative solutions to the problem may lie with manipulations of the early embryonic environment. I t has been shown that the embryonic environment plays a crucial role in the performance of fish later in life. For example, tempe rature during early life appears to influence growth and immune function. Here we explore whether embryonic temperature impacts the smoltification process of Atlantic salmon.
Materials and methods
Atlantic salmon embryos were exposed to d ifferent temperatures (4C and 8C) between fertilization and the ‘eyed-stage’. Afterwards, similar temperature profiles have been applied . Smoltification was induced using a standard photoperiod regime. At consecutive time points gene expression levels of smoltification and oxidative stress markers were analysed in, respectively, gill and liver tissue. Hepatocytes of postsmolts were isolated and exposed to various stressors. Furthermore, blood serum metabolomics are currently being analysed.
Results
Our preliminary results show that p erformance with respect to growth was not significantly impacted by embryonic temperature . Whereas the expression levels of the smoltification markers nka1a and nka1b in the gill showed similar patterns between the two temperature groups , s100a and cftr2 showed opposite patterns. The o xidative stress marker gpx increased in the low temperature group, while cat and cu/znsod decreased over time in the 8C group with respect to the 4C group. Hepatocytes showed little differences between the embryonic temperature groups in their response towards hydrogen peroxide, polyIC or LPS.
Conclusion
In order to improve the robustness of Atlantic salmon during its later life phases, the embryonic environment should be taken into consideration. It appears that the embryonic temperature may influence smoltification.
Acknowledgements
This study was funded by the Research Council of Norway (COOLFISH #325571; GB COOLSMOLT2.0 #194050) and the FHF-Norwegian Seafood Research Fund (Salmocode #901864).