Data from: Divergent immunity and energetic programs in the gills of migratory and resident Oncorhynchus mykiss

Divergent life history strategies occur in steelhead or rainbow trout
Oncorhynchus mykiss, and many populations produce both migrant (anadromous
fish that move to the ocean after rearing) and resident (do not migrate
and remain in fresh water) individuals. Mechanisms leading to each type
are only partially understood; while the general tendency of a population
is heritable, individual tendency may be plastic, influenced by local
environment. Steelhead hatchery programmes aim to mitigate losses in wild
stocks by producing trout that will migrate to the ocean and not compete
with wild trout for limited freshwater resources. To increase our
understanding of gill function in these migratory or resident phenotypes,
here we compare gill transcriptome profiles of hatchery-released fish
either at the release site (residents) or five river kilometres downstream
while still in full fresh water (migrants). To test whether any of these
genes can be used as predictive markers for smoltification, we compared
these genes between migrant-like and undifferentiated trout while still in
the hatchery in a common environment (prerelease). Results confirmed the
gradual process of smoltification, and the importance of energetics, gill
remodelling and ion transport capacity for migrants. Additionally,
residents overexpressed transcripts involved in antiviral defences,
potentially for immune surveillance via dendritic cells in the gills. The
best smoltification marker candidate was protein s100a4, expression of
which was highly correlated with Na(+) , K(+) ATPase (NKA) activity and
smolt-like morphology in pre- and postrelease trout gills.