Megens H-J †, Leon K †, Consuegra S , Jordan W*, Hindar K#,
Stet RJM †
† Cell Biology and Immunology Group, Wageningen University, Wageningen,
The Netherlands
* Zoological Society of London, Institute of Zoology, London, UK
# Norwegian Institute for Nature Research (NINA), Trondheim, Norway.
In the past decades, wild salmonid populations have suffered from the influence of large-scale culturing of farmed conspecifics. Some of the chief effects are the introduction of farmed, semi-domesticated fish, and the introduction of non-native diseases. This may lead to overall decline of wild populations, but may also lead to an alteration of locally adapted populations, either by selection or introduction of foreign genes. Our aim is to investigate how the composition of immune response genes changes as a result of this human influence. The Major Histocompatibility Complex plays an important role in immunity to disease. While truly complex in most vertebrates, salmonids have a minimal essential set of genes: a single class I and (unlinked) class II locus. Such a simple organization of Major Histocompatibility genes helps in detecting selection. We studied the association of MH alleles with embedded (mini and micro) satellite markers. This study has greatly enhanced our understanding of MH variation in wild populations, and showed that marker variation can be used to study MH allelic composition. This toolkit is currently implemented to screen various recent populations of Atlantic salmon in Norway, and is extended to populations from before known impacts, such as furunculosis outbreaks in the early 90’s, by using archived scales material. Contrasting changes in MHC variation with changes in a number of presumed neutral microsatellite markers will allow us to distinguish between effects of drift and selection.
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