Early experience and reproductive morph both affect brain morphology in adult male Chinook salmon (Oncorhynchus tshawytscha)

Abstract

It is clear that brain size and structure can be greatly influenced by the environment, and in fish, factors such as habitat complexity, rearing environment, and reproductive status have been shown to affect brain morphology and behaviour, but it is unclear how long these effects last. The objective of the current study was to investigate variability in overall brain size and particular brain regions of male Chinook salmon (Oncorhynchus tshawytscha) through the evaluation of potential driving forces -environment and reproductive morph. By comparing fish from different rearing environments and different male reproductive morphs (hooknose versus jack), the current research assessed the influence of each of these factors on overall brain size and on select brain regions. Male hooknose salmon had relatively smaller brains, once corrected for body size, than male jack salmon, suggesting possible trade-offs between somatic and brain development. Fish reared in hatchery environments but released into the wild as presmolts still had relatively larger brains than their wild counterparts, despite sharing wild habitats for over 3 years, suggesting persistent effects of hatchery rearing. Taken together, these results show that the difference in reproductive morphs can substantially impact brain morphology and that short-term environmental influences can have persistent effects throughout ontogeny.Résumé : Il est clairement établi que le milieu ambiant peut avoir une grande incidence sur la taille et la structure du cerveau. Chez les poissons, il a notamment été démontré que des facteurs comme la complexité de l'habitat, le milieu d'alevinage et l'état de reproduction influencent la morphologie et le comportement du cerveau, bien que la durée de ces effets ne soit pas bien connue. L'objectif de l'étude consiste à examiner la variabilité de la taille globale et de régions précises du cerveau de saumons quinnats (Oncorhynchus tshawytscha) mâles en évaluant des déterminants potentiels, comme le milieu et la forme reproductrice. En comparant des poissons de différents milieux d'alevinage et de différentes formes reproductrices mâles (bécards et furtifs), l'étude évalue l'influence de chacun de ces facteurs sur la taille globale et de différentes régions du cerveau. Les mâles bécards ont des cerveaux relativement plus petits, une fois leur taille pondérée selon la taille du corps, que les mâles furtifs, ce qui semble indiquer de possibles compromis entre le développement somatique et celui du cerveau. Les poissons issus d'écloserie relâchés dans la nature au stade de pré-saumoneau présentent des cerveaux relativement plus imposants que leurs congénères sauvages, malgré le fait qu'ils aient partagé les mêmes habitats naturels pendant plus de trois ans, ce qui indiquerait la persistance des effets de l'élevage en écloserie. Collectivement, ces résultats démontrent que la forme reproductrice peut avoir une incidence significative sur la morphologie du cerveau et que des influences de courte durée du milieu ambiant peuvent avoir des e...

Environment‐dependent plasticity and ontogenetic changes in the brain of hatchery‐reared Atlantic salmon

“…For instance, Atlantic salmon individuals being reared continuously in the hatchery (the same hatchery as in the present study) had a higher brain:body mass ratio than individuals that were released into the wild half a year earlier (Näslund et al ., ). Hatchery‐reared chinook salmon Oncorhynchus tshawytscha , originating from wild parents and being released as pre‐smolts, were found to have larger relative brain size than wild conspecifics, even after 3 years at sea (Wiper, Britton & Higgs, ). Investigating male clonal lines of rainbow trout, domesticated lines (>10 generations in hatchery) had larger brains than wild lines (wild parents) (Campbell et al ., ).…”

Microhabitat Use Affects Brain Size and Structure in Intertidal Gobies

“…Brain size has a strong positive correlation to body size, brain/ body size ratios decrease as body size increases, and brain size has a tendency to show a stronger increase with increasing body size during early ontogeny rather than adulthood [see Striedter, 2005, for a detailed review of these brain-body size relationships]. To control for these allometric effects, we calculated the relative lobe volume for each fish specimen [Bullmore et al, 1995;Burish et al, 2004;Wiper et al, 2014]. For example, when examining the relative lobe volume, body size was controlled for by dividing the lobe volume by the total brain volume to give the relative value (i.e.…”

Variation in Brain Morphology of Intertidal Gobies: A Comparison of Methodologies Used to Quantitatively Assess Brain Volumes in Fish

“…To control for these allometric effects, we calculated the relative lobe volume for each fish specimen [Bullmore et al, 1995;Burish et al, 2004;Wiper et al, 2014]. For example, when examining relative lobe volume, body size was controlled for by dividing lobe volume by total brain volume to give the relative value (i.e.…”

“…Brain size and structure have been correlated with spatial complexity within a habitat, dietary requirements and a range of social behaviours in comparative studies on a range of taxa, including primates [Barton, 1996;Reader and Laland, 2002], birds [Healy and Guilford, 1990;Clayton, 2001], ungulates [Shultz and Dunbar, 2006] and more recently fishes [Pollen et al, 2007;Gonzalez-Voyer and Kolm, 2010;Wilson and McLaughlin, 2010;Costa et al, 2011;Kotrschal et al, 2012a, b;Lecchini et al, 2014;Wiper et al, 2014]. These correlations were generated by determining brain volumes using the ellipsoid method and histology, and this study has added a further method for consideration, micro-CT.…”