Data from: Neutral genetic variation in adult Chinook salmon (Oncorhynchus tshawytscha) affects brain-to-body trade-off and brain laterality

Low levels of heterozygosity can have detrimental effects on life history
and growth characteristics of organisms but more subtle effects such as
those on trade-offs of expensive tissues and morphological laterality,
especially of the brain, have not been explicitly tested. The objective of
the current study was to investigate how estimated differences in
heterozygosity may potentially affect brain-to-body trade-offs and to
explore how these heterozygosity differences may affect differential brain
growth, focusing on directional asymmetry in adult Chinook salmon
(Oncorhynchus tshawytscha) using the laterality and absolute laterality
indices. Level of inbreeding was estimated as mean microsatellite
heterozygosity resulting in four ‘inbreeding level groups’ (Very High,
High, Medium, Low). A higher inbreeding level corresponded with a
decreased brain-to-body ratio, thus a decrease in investment in brain
tissue, and also showed a decrease in the laterality index for the
cerebellum, where the left hemisphere was larger than the right across all
groups. These results begin to show the role that differences in
heterozygosity may play in differential tissue investment and in
morphological laterality, and may be useful in two ways. Firstly, the
results may be valuable for restocking programmes that wish to emphasize
brain or body growth when crossing adults to generate individuals for
release, as we show that genetic variation does affect these trade-offs.
Secondly, this study is one of the first examinations to test the
hypothesized relationship between genetic variation and laterality,
finding that in Chinook salmon there is potential for an effect of
inbreeding on lateralized morphology, but not in the expected direction.