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Differences in brain morphology of brown trout across stream, lake, and hatchery environment

The trade-off between cognitive capacity and developmental costs drive
brain size and morphology across fish species, but this pattern is less
explored at intraspecific level. Physical habitat complexity has been
proposed as a selection pressure on cognitive capacity that shapes brain
morphology of fishes, but development of brain is also inherently linked
to supply of energy and nutrients, particularly of omega-3 long-chain
polyunsaturated fatty acids (n-3 LC-PUFA). In this study, we compared
brain morphology of brown trout Salmo trutta from stream, lake, and
hatchery environments, which differ in physical complexity and availably
of dietary n-3 LC-PUFA ranging from low habitat complexity and high n-3
LC-PUFA availability in hatchery to high habitat complexity and low n-3
LC-PUFA availability in streams. We found that brain size, and size of
optic tectum and telencephalon differed across the three habitats, being
largest in lake fish. We suggest that these differences appeared to
associate with diet quality and habitat specific behavioural adaptations
rather than physical habitat complexity.