AUTHOR=Krasnov Aleksei , Burgerhout Erik , Johnsen Hanne , Tveiten Helge , Bakke Anne F. , Lund Hege , Afanasyev Sergey , Rebl Alexander , Johansen Lill-Heidi TITLE=Development of Atlantic Salmon (Salmo salar L.) Under Hypoxic Conditions Induced Sustained Changes in Expression of Immune Genes and Reduced Resistance to Moritella viscosa JOURNAL=Frontiers in Ecology and Evolution VOLUME=9 YEAR=2021 URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2021.722218 DOI=10.3389/fevo.2021.722218 ISSN=2296-701X ABSTRACT=
Atlantic salmon is characterized with high sensitivity to low dissolved oxygen (DO) levels. Hypoxia can affect diverse biological processes with consequences that can be manifested immediately or with delay. Effects of hypoxia on the immune system and the resistance to a bacterial pathogen were investigated. Two groups were reared at, respectively, normal (NO, 80–100%) and low (LO, 60%) levels of DO over 10 months after which both groups were reared at NO. Smoltification was initiated after 13 months by a winter signal for 6 weeks, followed by constant light for 6 weeks. Samples were collected at the start and end of the constant light period. Expression of 92 immune and stress genes was analyzed in the gill, head kidney, and spleen using a Biomark HD. Most of differentially expressed genes showed higher levels in LO fish compared to NO fish; many immune genes were downregulated during smoltification and these changes were stronger in NO fish. A notable exception was pro-inflammatory genes upregulated in gill of NO fish. Further, salmon were challenged with