Variations in energy storage metabolism discriminate fresh and brackish/saltwater ecotypes in American glass eels

International audienceRecently, different ecotypes characterized by their migration form, have been genetically documented in the American eel, Anguilla rostrata. The aim of this study was to verify if energy status and differential abilities in mobilizing energy reserves could discriminate freshwater and brackish/saltwater ecotypes. To do so, analyses were done on glass eels at recruitment according to location of capture, date and salinity preference using eco-physiological and molecular tools. Salinity preference did not differ between ecotypes. Instead, we observed spatial and temporal variations adding to the body of evidence of genetic and environmental controls in the differentiation of ecotypes. Compared to the brackish/saltwater ecotype, the freshwater ecotype was larger and more pigmented, had 73.8 % lesser triacylglycerol content and 67,7 % higher glycogen content, and overexpressed 7.65 and 3.25 times respectively the transcripts of bile salt activated and triacylglycerol lipases. No variation in transcripts of glycogen phosphorylase, leptin and ghrelin was observed between ecotypes. For both ecotypes, level of pigmentation was higher and energetic reserves were lesser in glass eels arriving two weeks later. Our results suggest the existence of differential regulation mechanisms relative to energy metabolism between ecotypes and allow us to propose a new model of the physiological mechanisms underlying the recruitment of freshwater and brackish/saltwater ecotype in American glass eel. This new biological information contributes to the building knowledge on the distribution of ecotypes and on the internal factors involved in glass eel migration regulation, giving new indications to improve conservation measure for this species declared “threatened” in Canada

Is the energy status influencing dispersion in American glass eel?

International audienceThe American eel has a facultative catadromous life cycle. Spawning occurs in Sargasso Sea and growth occurs into freshwater or saltwater habitats over a wide geographical range. The selection of suitable habitat for growth begins at the glass eel stage. Based on the hypothesis of conditional dispersion strategy, energetic status would determine whether glass eels would express freshwater or saltwater preference. Glass eels were captured from two rivers from Nova Scotia and two rivers from Québec in 2011 and 2012. Following salinity preference experiments, glass eels were classified as “inactive” or as “active with preference for fresh water” and “active with preference for salt water”. They were anaesthetized in MS 222, weighed, measured and frozen in carbonic ice. Results indicate that glass eels expressing preference for freshwater had the highest condition factor. Total content of glycogen and lipids were measured in order to test whether or not the three groups of glass eels could be differentiated based on their energy status whatever the river and the year of fishing and results will be presented

Sex Chromosome Evolution, Heterochiasmy, and Physiological QTL in the Salmonid Brook Charr Salvelinus fontinalis

Whole-genome duplication (WGD) can have large impacts on genome evolution, and much remains unknown about these impacts. This includes the mechanisms of coping with a duplicated sex determination system and whether this has an impact on increasing the diversity of sex determination mechanisms. Other impacts include sexual conflict, where alleles having different optimums in each sex can result in sequestration of genes into nonrecombining sex chromosomes. Sex chromosome development itself may involve sex-specific recombination rate (i.e., heterochiasmy), which is also poorly understood. The family Salmonidae is a model system for these phenomena, having undergone autotetraploidization and subsequent rediploidization in most of the genome at the base of the lineage. The salmonid master sex determining gene is known, and many species have nonhomologous sex chromosomes, putatively due to transposition of this gene. In this study, we identify the sex chromosome of Brook Charr Salvelinus fontinalis and compare sex chromosome identities across the lineage (eight species and four genera). Although nonhomology is frequent, homologous sex chromosomes and other consistencies are present in distantly related species, indicating probable convergence on specific sex and neo-sex chromosomes. We also characterize strong heterochiasmy with 2.7-fold more crossovers in maternal than paternal haplotypes with paternal crossovers biased to chromosome ends. When considering only rediploidized chromosomes, the overall heterochiasmy trend remains, although with only 1.9-fold more recombination in the female than the male. Y chromosome crossovers are restricted to a single end of the chromosome, and this chromosome contains a large interspecific inversion, although its status between males and females remains unknown. Finally, we identify quantitative trait loci (QTL) for 21 unique growth, reproductive, and stress-related phenotypes to improve knowledge of the genetic architecture of these traits important to aquaculture and evolution

"Civelle, dis-nous où tu migres et nous te dirons à l'écotype auquel tu appartiens"

International audienceChez les anguilles d’Amérique, deux phénotypes ont été différenciés génétiquement : écotype d’eau douce dans l’estuaire et le fleuve St Laurent, écotype d’eau salée-saumâtre en Atlantique. Dans le but de clarifier les bases génétiques sous-jacentes de ces écotypes, l’expression de divers gènes a été caractérisée chez des civelles (le stade qui suit la métamorphose), dès leur arrivée en région estuarienne. Leur préférence de salinité individuelle a été considérée. Les civelles ont été capturées à deux reprises (intervalle d’une quinzaine de jours), dans l’estuaire de trois rivières graduellement éloignées de la zone de reproduction : rivière Mersey (côte Atlantique), rivière Gaspé (Golfe du St-Laurent), Grande-Rivière-Blanche (estuaire du St-Laurent). La préférence de salinité individuelle (eau douce, eau saumâtre ou eau salée) a été mesurée juste après la capture. Des analyses d’expression de gènes ont été effectuées par PCR en temps réel avec des sondes Taqman pour trois gènes de référence et quatorze gènes candidats impliqués dans le métabolisme des lipides, du glycogène, la métamorphose, les processus d’osmorégulation et de la croissance. Les résultats ont été analysés en deux temps selon deux hypothèses nulles: le métabolisme des lipides et du glycogène ne varient ni en fonction de l’origine, ni de la date de capture. Les traits reliés à la régulation de l’osmorégulation, de la croissance et de la métamorphose ne varient ni selon l’origine, ni selon la préférence de salinité individuelle. Des variations génétiques pour différents traits fonctionnels s’observent selon l’origine de capture. Les civelles capturées dans l’estuaire du Saint-Laurent sont caractérisées par de grande taille et montrent les plus hauts niveaux d’expression des lipases et du récepteur IGF-1. Les civelles capturées dans la région de Gaspé sont non pigmentées et de grande taille et montrent les niveaux d’expression les plus élevés pour les gènes représentatifs de l’axe thyroïdien. Enfin, les civelles capturées en Atlantique sont de petite taille et montrent les plus faibles niveaux d’expression de l’axe somatotrope et de l’enzyme déiodinase. Ces traits ne variaient ni en fonction de la préférence de salinité individuelle, ni de la date d’arrivée. Ces résultats montrent que des différences d’expression pouvant avoir des conséquences physiologiques importantes selon la rivière d’origine et qui pourraient résulter d’interactions gènes × environnent. Une meilleure compréhension de ces caractéristiques biologiques pourrait orienter les futures tentatives de réhabilitation du stock de civelles au Canada en apportant des informations utiles pour la gestion des pêcheries

Juvenile Greenland halibut (Reinhardtius hippoglossoides) growth in the context of rising temperature in the Estuary and Gulf of St. Lawrence

In a context of climate change, understanding the influence of temperature on fish species growth is important for the management of fisheries. The effect of increasing temperature on the growth of juvenile Greenland halibut (Reinhardtius hippoglossoides), a cold-water species, circum-continental in the Arctic, was investigated on juveniles that had been captured in the wild and kept in captivity. Mortality rate increased with higher temperature, from 4.5 % at 4.0 °C to 15.2 % at 7.5 °C. Relative growth (normalized in degree-days) was lower at 7.5 °C than at the two other temperatures tested. Food conversion efficiency, muscle energy content, and the Fulton condition index were not influenced by temperature, but food intake significantly increased over time at 5.5 °C. No clear difference in growth trajectories between sexes was highlighted. Overall, the results suggest that optimal temperature conditions were exceeded at 7.5 °C and that any further increase in temperature would significantly decrease survival and impair juvenile growth. With the current deep-water warming trends in the Estuary and Gulf of St. Lawrence, recruitment and commercial fishing of Greenland halibut may be impaired in the near future. -- Keywords : Greenland Halibut ; Growth ; Temperature ; Juveniles ; Fisheries ; Mortality

Evaluation of different extractions for the metabolite identification of malachite green in brook trout and shrimp

Applications of mass spectrometry-based metabolomics in food science have developed fast in the last decade. Sample preparation and data processing are critical in non-target/metabolomic workflows but there is currently no standardized protocol for the development of these methods. The impact of data processing parameters or the inclusion of a different matrix is not often taken into account during the selection of an extraction. Thus, this study aimed to investigate the impact of different extractions, e.g., QuEChERS, and data processing on the determination of malachite green metabolites in two different organisms, brook trout and shrimp. The results obtained confirm the need for a harmonized approach for the validation of non-target workflows, as depending on the comparison criteria, the matrix, the mode of ionization or data processing, a different extraction could be chosen. This study also identified for the first time des-methylated leucomalachite green as another metabolite in the two organisms. -- Keywords : Metabolites ; Aquaculture ; Veterinary drugs ; Anti-fungal treatment ; Extraction ; Suspect screening

Les civelles d’Amérique qui migrent sur la côte est canadienne ont-elle toutes les mêmes caractéristiques physiologiques ?

International audienceDepuis les années 80, la civelle d’Amérique a subi un important déclin dans le St Laurent, source importante de production de femelles chez cette espèce panmictique. Dans l’objectif de mieux comprendre la régulation physiologique de la migration de la civelle lorsqu’elle atteint les habitats côtiers, l’analyse des statuts énergétiques ainsi que l’expression des gènes codant pour des hormones impliquées dans l’osmorégulation ou pour leurs récepteurs a été effectuée sur des civelles capturées dès leur arrivée au niveau de trois rivières situées au Québec et en Nouvelle Écosse et ayant subi, post capture, un test de préférence de salinité. L’objectif était a) de vérifier si nous observons des différences régionales et ou des différences entre préférences de salinité (eau douce, eau salée et eau saumâtre) en fonction de la rivière où de la date d’arrivée et b) de vérifier ou rejeter, pour l’anguille américaine, le concept bien admis chez la civelle européenne et selon lequel le statut énergétique de la civelle à son arrivée en estuaire détermine sa préférence de salinité Les résultats des analyses des classes de lipides, des lipides totaux, de la concentration du glycogène total ainsi que les expressions relatives des gènes par la méthode de réaction en chaîne par polymérase à temps réel (qPCR) seront présentés.Ce projet doctorat a été élaboré étroitement avec la collaboration du laboratoire de Louis Bernatchez, le Ministère Pêches et Océans Canada, le Ministère des Forêts, de la Faune et des Parcs ainsi que les pêcheurs professionnels d’Atlantic Elver Inc

Novel Feed from Invasive Species is Beneficial to Walleye Aquaculture

Carnivorous fishes, such as the Walleye Sander vitreus, are nutritionally demanding for fish meal. A promising alternative to marine-origin fish meal, the supply of which has been stagnant in recent decades, is fish meal derived from undesirable freshwater species, such as the White Sucker Catostomus commersonii. To evaluate the relative value of such ingredients, we examined the growth performance of Walleye juveniles. Two dietary treatments were tested: an experimental (EXP) diet that was manufactured using White Sucker as fish meal in comparison with a commercial (COM) diet, EWOS Micro (EWOS Canada, Ltd.). Dietary lipid content was 15.1% and 16.8% for EXP and COM diets, respectively. The protein content was 50.4% and 57.6% for EXP and COM diets, respectively. The energy content was 5,098.76 ± 9.23 cal/g (mean ± SD) for the EXP diet and 5,134.47 ± 10.95 cal/g for the COM diet. Starting at 27 d posthatch, Walleye juveniles (initial weight [mean ± SD] = 0.03 ± 0.008 g; initial length = 15.7 ± 1.5 mm) were reared for 6 weeks in three replicate tanks for each treatment. Condition factor (0.83), final weight (1.12 ± 0.3 g), and weight gain (1.09 ± 0.06 g) were higher in fish that were fed the EXP diet. Similarly, the energetic lipid content of fish in the EXP treatment group (mean ± SD = 5.01 ± 0.45 g/kg) was also higher than that of fish fed the COM diet (3.30 ± 0.53 g/kg). Although the polar lipid content (membrane lipids) was similar in fish from the two treatments, the nutritional ratio for COM juveniles was over 1.5 for arachidonic acid and docosahexaenoic acid, indicating selective incorporation by juveniles and suggesting a potential dietary imbalance of these fatty acids. Furthermore, the higher observed selective incorporation of oleic acid in juveniles fed the EXP diet suggested that a higher value of this fatty acid in the EXP feed could have increased Walleye growth performance. Threonine was the main essential amino acid (AA; >18.5% of total AAs), while serine and glycine contributed the highest percentages of the nonessential AAs (>31% and 8.5% of total AAs, respectively). All three AAs, often considered limiting ingredients, are important to support growth and are involved in metabolic processes in some fish species. Our results demonstrate that feed pellets made with White Sucker fish meal improved growth in Walleye juveniles and can serve as a suitable and probably lower-cost regional alternative to marine fish meal in feeds for carnivorous fishes

Sex-Specific Co-expression Networks and Sex-Biased Gene Expression in the Salmonid Brook Charr <i>Salvelinus fontinalis</i>.

Networks of co-expressed genes produce complex phenotypes associated with functional novelty. Sex differences in gene expression levels or in the structure of gene co-expression networks can cause sexual dimorphism and may resolve sexually antagonistic selection. Here we used RNA-sequencing in the salmonid Brook Charr Salvelinus fontinalis to characterize sex-specific co-expression networks in the liver of 47 female and 53 male offspring. In both networks, modules were characterized for functional enrichment, hub gene identification, and associations with 15 growth, reproduction, and stress-related phenotypes. Modules were then evaluated for preservation in the opposite sex, and in the congener Arctic Charr Salvelinus alpinus Overall, more transcripts were assigned to a module in the female network than in the male network, which coincided with higher inter-individual gene expression and phenotype variation in the females. Most modules were preserved between sexes and species, including those involved in conserved cellular processes (e.g., translation, immune pathways). However, two sex-specific male modules were identified, and these may contribute to sexual dimorphism. To compare with the network analysis, differentially expressed transcripts were identified between the sexes, revealing a total of 16% of expressed transcripts as sex-biased. For both sexes, there was no overrepresentation of sex-biased genes or sex-specific modules on the putative sex chromosome. Sex-biased transcripts were also not overrepresented in sex-specific modules, and in fact highly male-biased transcripts were enriched in preserved modules. Comparative network analysis and differential expression analyses identified different aspects of sex differences in gene expression, and both provided new insights on the genes underlying sexual dimorphism in the salmonid Brook Charr

The brook trout Salvelinus fontinalis (Mitchill, 1814) in the Saint-Pierre and Miquelon archipelago: a review

L’archipel français de saint-Pierre et Miquelon (sPM) est situé à l’est de l’amérique du nord. L’omble de fontaine Salvelinus fontinalis (Mitchill, 1814) est la principale espèce pêchée à la ligne dans les eaux douces de sPM. nous présentons ici une synthèse des études locales et des essais d’élevage réalisés sur ce poisson. nous avons retrouvé des dizaines de documents datant du début des années 1980 qui visaient à élucider sa biologie et son écologie. À cette époque, les premiers essais d’élevage ont été réalisés à Miquelon puis à saint-Pierre, généralement par des bénévoles, et principalement à des fins de repeuplement ou pour développer la pêche spor-tive. ainsi, grâce au travail de nombreux passionnés encadrés occasionnellement par des chercheurs extérieurs, des connaissances ont été acquises sur la biologie, l’écologie et l’élevage de l’omble de fontaine sur l’archipel. Enfin, quelques suggestions pour des travaux ultérieurs (par exemple, la diversité génétique, la connectivité et l’expression génétique) sont présentées. // The French archipelago of Saint-Pierre and Miquelon (SPM) is located in eastern North America. Brook trout Salvelinus fontinalis (Mitchill, 1814) is the key angling species in SPM’s freshwater. Here we provide a synthesis of local studies and rearing trials performed on this fish. Dozens of documents were found dating back from the beginning of the 1980s that aimed to elucidate its biology and ecology. At that time, the first farming trials were conducted in Miquelon and then in Saint-Pierre, generally by volunteers, and mainly for restocking purposes or to develop sport fishing. As a result, thanks to the work of many enthusiasts occasionally supervised by outside researchers, knowledge was acquired on the biology, ecology and farming of brook trout on the archipelago. Finally, some suggestions for further works (e.g. genetic diversity, connectivity and gene expression) are presented. -- Keywords : Angling ; Aquaculture ; Brook trout ; Ecotourism