title: Triploidy alters brain morphology in pre-smolt Atlantic salmon Salmo salar: possible implications for behaviour.
abstract: Total brain mass and the volumes of five specific brain regions in diploid and triploid Atlantic salmon Salmo salar pre-smolts were measured using digital images. There were no significant differences (P > 0·05) in total brain mass when corrected for fork length, or the volumes of the optic tecta or hypothalamus when corrected for brain mass, between diploids and triploids. There was a significant effect (P < 0·01) of ploidy on the volume of the olfactory bulb, with it being 9·0% larger in diploids compared with triploids. The cerebellum and telencephalon, however, were significantly larger, 17 and 8% respectively, in triploids compared with diploids. Sex had no significant effect (P > 0·05) on total brain mass or the volumes of any measured brain region. As the olfactory bulbs, cerebellum and telencephalon are implicated in a number of functions, including foraging ability, aggression and spatial cognition, these results may explain some of the behavioural differences previously reported between diploids and triploids.
authors.affiliation: Department of Production Animal Clinical Sciences, Norwegian School of Veterinary Science, 0033 Oslo, Norway. tom.fraser@nvh.no
authors.forename: T W K
authors.initials: TW
authors.lastname: Fraser
authors.forename: P G
authors.initials: PG
authors.lastname: Fjelldal
authors.forename: J E
authors.initials: JE
authors.lastname: Skjæraasen
authors.forename: T
authors.initials: T
authors.lastname: Hansen
authors.forename: I
authors.initials: I
authors.lastname: Mayer
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D001921:Brain / Q000033:anatomy & histology*; D009929:Organ Size / Q000235:genetics; D020317:Salmo salar / Q000033:anatomy & histology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D057885:Triploidy