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Open Access Research article

Interpopulation differences in expression of candidate genes for salinity tolerance in winter migrating anadromous brown trout (Salmo trutta L.)

Peter F Larsen13*, Einar E Nielsen1, Anders Koed1, Dennis S Thomsen2, Pål A Olsvik4 and Volker Loeschcke3

Author Affiliations

1 Technical University of Denmark, Danish Institute for Fisheries Research, Department of Inland Fisheries, DK-8600 Silkeborg, Denmark

2 Svendborg County, Svendborgvej 135, DK-5762 Vester Skerninge, Denmark

3 University of Aarhus, Department of Biological Sciences, DK-8000 Aarhus C, Denmark

4 National Institute of Nutrition and Seafood Research, PO Box 2029 Nordnes, N-5817 Bergen, Norway

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BMC Genetics 2008, 9:12  doi:10.1186/1471-2156-9-12

Published: 29 January 2008

Abstract

Background

Winter migration of immature brown trout (Salmo trutta) into freshwater rivers has been hypothesized to result from physiologically stressful combinations of high salinity and low temperature in the sea.

Results

We sampled brown trout from two Danish populations entering different saline conditions and quantified expression of the hsp70 and Na/K-ATPases α 1b genes following acclimation to freshwater and full-strength seawater at 2°C and 10°C. An interaction effect of low temperature and high salinity on expression of both hsp70 and Na/K-ATPase α 1b was found in trout from the river entering high saline conditions, while a temperature independent up-regulation of both genes in full-strength seawater was found for trout entering marine conditions with lower salinities.

Conclusion

Overall our results support the hypothesis that physiologically stressful conditions in the sea drive sea-run brown trout into freshwater rivers in winter. However, our results also demonstrate intra-specific differences in expression of important stress and osmoregulative genes most likely reflecting adaptive differences between trout populations on a regional scale, thus strongly suggesting local adaptations driven by the local marine environment.