Transgenerational effects on body size and survival in Brook charr (Salvelinus fontinalis)

Abstract Higher temperatures are now observed in several ecosystems and act as new selective agents that shape traits and fitness of individuals. Transgenerational effects may be important in modulating adaptation of future generations and buffering negative impacts of temperature changes. The potential for these effects may be important in freshwater fish species, as temperature is a key abiotic component of their environment. Yet, still, relatively few studies have assessed the presence and importance of transgenerational effects under natural conditions. The purpose of this study was to test how parental thermal conditions influenced offspring growth and survival following stocking in Brook charr (Salvelinus fontinalis). To do so, part of the breeders were exposed to a “cold” treatment while others were exposed to a “warm” treatment during the final steps of gonad maturation (constant 2°C difference between treatments along the seasonal temperature decrease). The impact on offspring of a selection treatment targeting production traits of interest (absence of sexual maturation at 1+, combined with increased growth) in breeders was also evaluated. After 7–8 months of growth in captivity, offspring were stocked in natural lakes. Their growth and survival were assessed about a year later. Offspring from “cold” breeders showed lower survival than those from “warm” breeders and the selection treatment had no effect on survival. However, the selection treatment was linked to lower Fulton's condition index, which, in turn, was positively correlated to survival in lakes. This study highlights the importance of working in ecological/industrial context to fully assess the different impacts of transgenerational effects on traits and survival. Our results also have important implications for stocking practices used to support the sport fishing industry

A gene expression approach to understanding growth in brook charr Salvelinus fontinalis: a case of culture success after five generations of selection

International audienceFollowing a selection program carried out for five generations in our lab, we examined the impact of selection on the growth regulation pathways occurring in the brain, hypophysis, liver, and muscle in brook charr. Thirteen families from the selection program and 16 control families were sampled at age 1+. The four best and the four worst performing families were sampled in each line. The gene expression levels of three reference and 10 candidate genes were analyzed by real-time PCR. Family performance and individual size were shown to have no impact on gene expression levels. However, selection was itself the key factor for differential expression. The gh/igf-1 axis in the selected line was upregulated, including pituitary igf-1r, liver ghr and igf-1, and white muscle ghr and igf-1r; this resulted in better growth performance (weight and length). However, improved growth performance did not seem to be related to the differential expression of genes involved in appetite control (npy, lepr, grl, srifr) or muscle construction (mhc, myog). This study highlights how transcriptomics may be useful for understanding the roles of different key endocrine steps regulating physiological performance. Large variations still exist in the selected line, indicating that the full genetic selection potential has not yet been reached

A gene expression approach to understanding growth in brook charr Salvelinus fontinalis: a case of culture success after five generations of selection

International audienceFollowing a selection program carried out for five generations in our lab, we examined the impact of selection on the growth regulation pathways occurring in the brain, hypophysis, liver, and muscle in brook charr. Thirteen families from the selection program and 16 control families were sampled at age 1+. The four best and the four worst performing families were sampled in each line. The gene expression levels of three reference and 10 candidate genes were analyzed by real-time PCR. Family performance and individual size were shown to have no impact on gene expression levels. However, selection was itself the key factor for differential expression. The gh/igf-1 axis in the selected line was upregulated, including pituitary igf-1r, liver ghr and igf-1, and white muscle ghr and igf-1r; this resulted in better growth performance (weight and length). However, improved growth performance did not seem to be related to the differential expression of genes involved in appetite control (npy, lepr, grl, srifr) or muscle construction (mhc, myog). This study highlights how transcriptomics may be useful for understanding the roles of different key endocrine steps regulating physiological performance. Large variations still exist in the selected line, indicating that the full genetic selection potential has not yet been reached

Growth regulation in brook charr Salvelinus fontinalis

Fish growth can be modulated through genetic selection. However, it is not known whether growth regulatory mechanisms modulated by genetic selection can provide information about phenotypic growth variations among families or populations. Following a five-generation breeding program that selected for the absence of early sexual maturity and increased growth in brook charr we aimed to understand how the genetic selection process modifies the growth regulatory pathway of brook charr at the molecular level. To achieve this, we studied the regulation of growth traits at three different levels: 1) between lines—one under selection, the other not, 2) among-families expressing differences in average growth phenotypes, which we termed family performance, and 3) among individuals within families that expressed extreme growth phenotypes, which we termed slow- and fast-growing. At age 1+, individuals from four of the highest performing and four of the lowest performing families in terms of growth were sampled in both the control and selected lines. The gene expression levels of three reference and ten target genes were analyzed by real-time PCR. Results showed that better growth performance (in terms of weight and length at age) in the selected line was associated with an upregulation in the expression of genes involved in the growth hormone (GH)/insulin growth factor-1 (IGF-1) axis, including the igf-1 receptor in pituitary; the gh-1 receptor and igf-1 in liver; and ghr and igf-1r in white muscle. When looking at gene expression within families, family performance and individual phenotypes were associated with upregulations of the leptin receptor and neuropeptid Y—genes related to appetite regulation—in the slower-growing phenotypes. However, other genes related to appetite (ghrelin, somatostatin) or involved in muscle growth (myosin heavy chain, myogenin) were not differentially expressed. This study highlights how transcriptomics may improve our understanding of the roles of different key endocrine steps that regulate physiological performance. Large variations in growth still exist in the selected line, indicating that the full genetic selection potential has not been reached

Growth regulation in brook charr Salvelinus fontinalis

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La transcriptomique : un outil pour améliorer la gestion des espèces aquacoles et halieutiques

International audienceLe but de ce travail a été d’explorer comment l’expression de gènes (transcriptomique) peut apporter des informations utiles dans la gestion des espèces d’intérêt aquacole (omble de fontaine Salvelinus fontinalis) et halieutique (le sébaste Atlantique Sébastes mentella). Un des aspects les plus importants dans la gestion des espèces est la compréhension de la croissance et du métabolisme, et les études au niveau moléculaire peuvent fournir des informations à un niveau de régulation très en amont des effets mesurables au niveau phénotypique. L’un des principaux apports de cette recherche a été de mettre en évidence les différences d’expression de gènes associées à la régulation de la croissance en fonction de la présence ou non de sélection génétique, de la famille et du phénotype chez l’omble de fontaine. Le rôle de certains gènes associés au contrôle de l’appétit et comment leur expression peut être associée à la performance individuelle et familiale est à souligner. Ces outils se sont également révélés utiles pour évaluer l’apport de la régulation hormonale et métabolique pour comparer la boucle de régulation de la croissance du sébaste atlantique, une espèce dont les conditions d’habitat (profondeur, pression, obscurité) sont difficiles à reproduire en milieu expérimental, à l’intérieur d’une vaste zone géographique couvrant l’estuaire et le golfe du Saint-Laurent

La transcriptomique : un outil pour améliorer la gestion des espèces aquacoles et halieutiques

International audienceLe but de ce travail a été d’explorer comment l’expression de gènes (transcriptomique) peut apporter des informations utiles dans la gestion des espèces d’intérêt aquacole (omble de fontaine Salvelinus fontinalis) et halieutique (le sébaste Atlantique Sébastes mentella). Un des aspects les plus importants dans la gestion des espèces est la compréhension de la croissance et du métabolisme, et les études au niveau moléculaire peuvent fournir des informations à un niveau de régulation très en amont des effets mesurables au niveau phénotypique. L’un des principaux apports de cette recherche a été de mettre en évidence les différences d’expression de gènes associées à la régulation de la croissance en fonction de la présence ou non de sélection génétique, de la famille et du phénotype chez l’omble de fontaine. Le rôle de certains gènes associés au contrôle de l’appétit et comment leur expression peut être associée à la performance individuelle et familiale est à souligner. Ces outils se sont également révélés utiles pour évaluer l’apport de la régulation hormonale et métabolique pour comparer la boucle de régulation de la croissance du sébaste atlantique, une espèce dont les conditions d’habitat (profondeur, pression, obscurité) sont difficiles à reproduire en milieu expérimental, à l’intérieur d’une vaste zone géographique couvrant l’estuaire et le golfe du Saint-Laurent

Evidence of parasite-mediated disruptive selection on genetic diversity in a wild fish population

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