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International audience; Cognitive abilities were studied in rainbow trout, the first continental fish production in Europe. Increasing public concern for the welfare of farmed-fish species highlighted the need for better knowledge of the cognitive status of fish. We trained and tested 15 rainbow trout with an operant conditioning device composed of self-feeders positioned in front of visual stimuli displayed on a screen. The device was coupled with a two-alternative forced-choice (2-AFC) paradigm to test whether rainbow trout can discriminate 2-D photographs of conspecifics (S+) from different visual stimuli (S-). The S- were applied in four stages, the last three stages representing increasing discrimination difficulty: (1) blue shapes; (2) black shape (star); (3) photograph of an object (among a pool of 60); (4) photograph of another fish species (among a pool of 60). Nine fish (out of 15) correctly managed to activate the conditioning device after 30–150 trials. The rainbow trout were able to discriminate images of conspecifics from an abstract shape (five individuals out of five) or objects (four out of five) but not from other fish species. Their ability to learn the category "fish shape" rather than distinguishing between conspecifics and heterospecifics is discussed. The successful visual discrimination task using this complex operant conditioning device is particularly remarkable and novel for this farmed-fish species, and could be exploited to develop cognitive enrichments in future farming systems. This device can also be added to the existing repertoire of testing devices suitable for investigating cognitive abilities in fish.

Rainbow trout has a male heterogametic (XY) sex determination system controlled by a major sex-determining gene, sdY. Unexpectedly, a few phenotypically masculinised fish are regularly observed in all-female farmed trout stocks. To better understand the genetic determinism underlying spontaneous maleness in XX-rainbow trout, we recorded the phenotypic sex of 20,210 XX-rainbow trout from a French farm population at 10 and 15 months post-hatching. The overall masculinisation rate was 1.45%. We performed two genome-wide association studies (GWAS) on a subsample of 1139 individuals classified as females, intersex or males using either medium-throughput genotyping (31,811 SNPs) or whole-genome sequencing (WGS, 8.7 million SNPs). The genomic heritability of maleness ranged between 0.48 and 0.62 depending on the method and the number of SNPs used for the estimation. At the 31K SNPs level, we detected four QTL on three chromosomes (Omy1, Omy12 and Omy20). Using WGS information, we narrowed down the positions of the two QTL detected on Omy1 to 96 kb and 347 kb respectively, with the second QTL explaining up to 14% of the total genetic variance of maleness. Within this QTL, we detected three putative candidate genes, fgfa8, cyp17a1 and an uncharacterised protein (LOC110527930), which might be involved in spontaneous maleness of XX-female rainbow trout.

Successful realized selection response for fillet yield in rainbow trout Oncorhynchus mykiss. World Aquaculture 2018

National audience; Estimation de la diversité génétique entre et intra lignées françaises de truite arc en ciel. 6. Journées de la Recherche Filière Piscicole

This study aimed to study the cognitive abilities of a species widely used by humans for food production: the rainbow trout. A better knowledge of its mental abilities could aim to better understand how this farmed animal perceives its environment and what it may experience when its welfare is compromised. To do so, an innovative operant conditioning device was designed. This one was coupled with a 2-AFC paradigm, a powerful and frequently used test for behavioural studies, to test whether this species can discriminate its conspecifics represented on 2D photographs, from different visual stimuli. We showed that rainbow trout is able to differentiate its congeners from abstract shapes or objects, which is consistent with the ecology of the species. Moreover, they managed to activate a self-feeder individually in an unknow environment, which is particularly noteworthy for a gregarious and neophobic species. As far as we know, this is the first study demonstrating such cognitive performance in rainbow trout. Further investigations will aim to highlight other, even more complex cognitive abilities (working memory, categorization abilities and concept learning). In this way, the contribution to the knowledge of the still under-documented farmed animals' cognitive abilities will continue and will inform the societal debate conderning animal consciousness.; Cette étude visait à étudier les capacités cognitives d'une espèce couramment utilisée par l'homme dans la chaîne alimentaire : la truite arc-en-ciel. Une meilleure connaissance de ses capacités mentales permettrait de mieux comprendre la façon dont cet animal de rente perçoit son environnement et ce qu'il peut éprouver lorsque son bien-être est compromis. Pour ce faire, un dispositif de conditionnement opérant innovant a été conçu. Celui-ci a été couplé à un paradigme de 2-AFC, un test puissant et fréquemment utilisé dans le cas d'études comportementales, afin de tester si cette espèce peut distinguer ses congénères représentées en 2D sur des photographies, de différents stimuli visuels. Nous avons montré que la truite arc-en-ciel est capable de différencier ses congénères de formes abstraites ou d'objets, ce qui coïncide avec l'écologie de l'espèce. De plus, elles ont appris à activer un self-feeder individuellement dans un environnement inconnu, ce qui est particulièrement remarquable pour une espèce grégaire et néophobe. A notre connaissance, il s'agit de la première étude montrant de telles performances cognitives chez la truite arc-en-ciel. Des recherches complémentaires viseront à mettre en évidence d'autres capacités cognitives encore plus complexes (mémoire de travail, capacités de catégorisation et apprentissage de concepts). Ainsi l'apport de connaissances sur les capacités cognitives des animaux de rente, encore trop peu documentées se poursuivront, et alimenteront le débat sociétal concernant la conscience animale.

Les organismes multicellulaires (métazoaires) possèdent des cellules souches embryonnaires àl’origine de la formation de l’organisme et des cellules souches adultes responsables du maintien del’intégrité des tissus au cours de la vie. Les propriétés principales de ces cellules souches adultes sontl’auto-renouvèlement et la différenciation, ce qui permet d’assurer à l’organisme un apport appropriéen cellules différenciées et spécialisées.

International audience; Marker-based parentage assignment provides the opportunity to investigate factors of efficiency for mixed-family designs and factorial mating. In such designs, family size is both uncontrolled and small, which may be thought to limit the accuracy of estimated breeding values (EBVs). The objective of this work was to estimate the accuracy of EBVs of growth and quality traits in a large factorial mating design and in commercial breeding conditions. An expected six hundred full-sib families of rainbow trout Oncorhynchus mykiss (2042 fish in total) were produced by ten factorial matings of six dams with ten sires. Fish were phenotyped for body weight, carcass yield, fillet yield, fillet fat content and fi llet colour, and family information was recovered using microsatellite markers. The accuracy of EBVs was estimated using or removing individual performance to mimic combined family selection (with individual phenotype) or sib selection (without individual phenotype). The traits investigated had medium to high heritability (0.17–0.58). High to very high accuracy (0.630–0.817) was estimated for combined family selection. The accuracy of sib selection (not using individual phenotype) was 18–22% lower (0.542–0.638), but remained in the upper range reported for such traits. This level of accuracy was higher than those reported in conventional breeding programs using separate family rearing. This was true even for families with a very low number of full-sibs. Individual EBV accuracy was more closely linked to the total number of full- and half-sibs of each fish than to its number of full-sibs. We hypothesize that this was due to the factorial mating, which led to a high number of the genetic ties between sibs. These results highlight the possibility of introducing precise estimated breeding values for quality traits into combined or sib selection in breeding programs when using mixed families from factorial designs and marker- based parentage assignment in aquaculture species

The present study investigates the effects of dietary phospholipids (PL) on intestinal lipid absorption in fry and early juvenile stages of rainbow trout ( Oncorhynchus mykiss ) fed fresh or oxidized lipids. Six semi-purified casein-based diets were formulated with 12% fresh or oxidized fish oil and 6% PL supplied as soybean lecithin or egg lecithin or 6% soybean oil for PL-free diets. Each diet was distributed to 3 replicate tanks of 700 swim-up fry (initial mean body weight: 66 mg) or 200 early juvenile fish (initial mean body weight: 455 mg) over a 3-week or 17-week growth trial at a water temperature of 17 °C. Feeding oxidized compared to fresh lipids significantly reduced body weight of both fry and juvenile trout (0.15 ± 0.02 vs. 0.28 ± 0.07 g and 10 ± 2 vs. 22 ± 2 g, respectively). At fry stages, within groups fed fresh lipids, trout fry fed the PL-supplemented diets had a significantly higher final body weight than fry fed the PL-free diet (0.31 ± 0.06 vs. 0.21 ± 0.02 g). Histological examination revealed a higher occurrence of intestinal steatosis (accumulation of large lipid droplets in the enterocytes of the anterior intestine) in fish fed the PL-free diet compared to fish fed PL-supplemented diets at fry stages (13/16 vs. 1/32), whereas no significant differences were recorded at juvenile stages (1/18 vs. 0/18). The levels of circulating total cholesterol, triacylglycerol (TAG) and PL in the juvenile fish were not significantly modified by dietary PL supplementation whereas the plasma TAG/PL ratio was lower in juvenile fish fed oxidized compared to fresh lipids (0.31 ± 0.06 vs. 0.45 ± 0.08). At the fry stages, within groups fed fresh lipids, expression of the gene coding for apolipoprotein B (apoB) was 2.3-fold reduced in the intestine of fish fed the PL-free diet compared to the PL-supplemented diets whereas no significant difference was recorded at juvenile stages. The expression of other apolipoproteins or key-enzymes involved in intestinal lipoprotein synthesis was not significantly modified by dietary PL supplementation. In conclusion, the results indicate that the beneficial effect of dietary PL on growth and intestinal lipid absorption is restricted to the fry stages and support previous opinions that PL are needed for intestinal TAG absorption. The limiting step seems to be the synthesis of apoB by the enterocytes in rainbow trout fry fed fresh lipids but this requires further investigation in fish fed oxidized lipids.

Ontogenetic niche shift should occur when the ratio of growth opportunities to mortality risk becomes higher in the subsequent habitat. While most studies have focused on size to understand the timing of these shifts, an endogenous factor like energetic status (interaction between energy available and energy requirements) appears as a natural candidate to integrate and analyze the growth trade-off between habitats. In this study, we measure energetic content and metabolic rate of individual brown trout (Salmo trutta) fry at emergence from gravel to investigate the influence of energetic status on the timing of this critical ontogenetic niche shift. In addition, as offspring energetic status is subject to parental effects, we examine how females could maximize their own fitness by influencing offspring emergence timing. Our results demonstrate that emergence from gravel is influenced by energetic status. Individuals that emerge first have a higher energetic content but deplete it faster because of a higher metabolic rate. We also find that female fecundity is positively related to emergence period duration. Moreover, our results suggest that females may decrease kin competition during the critical period of emergence by influencing the energetic status of offspring, thus, maximizing their own fitness. Our results help elucidate the mechanisms underlying early ontogenetic niche shifts in juvenile fish and suggest reasons why maternal investment can be so variable within populations.

In this study, the effect of acute and chronic insulin treatments on major factors involved in the control of muscle protein turnover were investigated in rainbow trout (Oncorhynchus mykiss). We found that acute but not chronic insulin administration leads to the induction of the phosphorylation of several key factors (IRS1, TOR and 4E-BP1) involved in the control of the protein synthesis and to the concomitant down-regulation of the expression of ubiquitin–proteasome-related genes (atrogin1, C2, C9) and the calpains inhibitor calpastatin. In contrast, no modification of autophagy-related gene (LC3B, gabarpl1, atg4b) expressions was observed suggesting that the mechanisms controlling this proteolytic route have diverged throughout the evolution. Overall, these results provide a possible explanation of the growth-promoting properties of insulin previously described in fish and indicate that this hormone acutely administrated is able to exert a regulatory influence on various factors associated with growth in skeletal muscle.

Tbx1 is a member of the T-box transcription factor gene family involved in embryogenesis and organogenesis. Recently, within a pan-genomic screen using rainbow trout (Oncorhynchus mykiss) cDNA microarrays, we identified a tbx1 homolog with testicular over-expression during sex differentiation. Here, we characterized two very similar rainbow trout tbx1 paralogs, tbx1a and tbx1b. In adult tissues, tbx1a expression is restricted to the gonads, with high expression in the testis, while tbx1b is more widely expressed in gonads, gills, brains, muscle, and skin. During gonadal differentiation, both genes are differentially expressed in favor of testis formation shortly after hatching. These genes are expressed in somatic cells surrounding germ cells of the differentiating testis, while no or only weak expression was observed in the differentiating ovary. tbx1a and tbx1b were also both down-regulated in the differentiating testis during feminization with estrogens and up-regulated in the differentiating ovary during masculinization with an aromatase inhibitor. These results suggest that tbx1a and tbx1b are probably involved in the regulation of testicular differentiation in rainbow trout. Since Tbx1 is known to interact with the retinoic acid (RA) signaling pathway, we also examined the effect of RA on the rainbow trout tbx1 expression pattern. Expression of tbx1a and tbx1b was down-regulated in RA-treated male gonads, suggesting that tbx1 interacts with the RA signaling pathway and thus could be involved in the control of rainbow trout gonadal differentiation.

SUMMARY The origin for the poor glucose utilization in carnivorous fish species fed high carbohydrate diets remains under debate. In the present study, we have fed rainbow trout a diet containing 30% carbohydrate for 1 or 5 days. In both cases, fish were implanted with mini-osmotic pumps releasing 0.7 i.u. kg–1 day–1 bovine insulin, and mRNA transcripts and the protein phosphorylation status of proteins controlling glycemia and glucose-related metabolism were studied in fish killed 6 h after the last meal. We demonstrate that when the exposure occurs over a short term (30 h), insulin exerts beneficial actions on trout glucose homeostasis, including a lowered glycemia and increased hepatic lipogenic and glycogenic potentials. However, when trout were fed for 5 days, these beneficial actions of insulin infusion were no longer observed. Thus, the increased lipogenic potential observed after one single meal was not present, and this together with the increased glycogenesis and the decreased glucose exported to the blood from the liver explains the lack of hypoglycemic action of insulin. The fact that insulin improved glucose homeostasis when administrated over a short time period implies that endogenous insulin secretion is inadequate in trout to deal with this amount of dietary carbohydrates. Moreover, the fact that a longer exposure to insulin resulted in a reduced response indicates that the rainbow trout is sensitive to insulin, re-enforcing the hypothesis that the hyperglycemia observed following a high carbohydrate meal is an insulin secretion issue rather an insulin action issue.

International audience; The abilities of triploid and diploid red blood cells to face an osmotic challenge were investigated. Erythrocytes from triploid rainbow trout were significantly more resistant to osmotic lysis than those from immature diploids of the same age. This observation could be related to the initial cell's shape and size and to the difference in cell surface area-to-volume ratio. Comparison of changes in intracellular ionic concentration (K(+), Cl(-)) associated with cell volume regulatory processes did not indicate any mechanistic explanation for this difference in osmotic resistance. This difference gradually disappeared during diploid sexual maturation. The early acquisition of high resistance to haemolysis by triploid erythrocytes is surprising since diploids appear to require time consuming and complex physiological changes to achieve a similar capability. Therefore, triploid cells appear as interesting models for investigation into cell physiology. (C) 2010 Elsevier B.V. All rights reserved.

International audience; The effects of dietary levels of phosphorus (P) and calcium (Ca) on skeletal development and mineral deposition in rainbow trout (Oncorhynchus mykiss) fry were studied. Six semi-purified diets were formulated with graded levels of P and Ca. The basal diet A contained only P supplied by casein at 0.5% of dry matter. Other cliets B,C, D and E were supplemented with 0.4, 0.8, 1.2 and 1.6% P supplied as a 1:1 mixture of NaH(2)PO(4)/KH(2)PO(4) resulting in 0.8, 1.2, 1.6 and 2.2% total P, respectively. These five diets were supplemented with 1% Ca supplied as CaCO(3) whereas another diet F, supplemented with 0.8% P,was Ca-free. Each diet was distributed to 3 replicate tanks of 600 swim-up fry (initial mean weight: 0.1 g) at a water temperature of 17 degrees C over a 12-week growth trial. Fish were handfed 6 times a day to visual satiety. There was no significant effect of dietary P (0 to 1.6%) or Ca (0 or 1%) supplementation on growth (final mean weight: 4.0 +/- 1.2 g). Survival of fish fed with diet E containing a high level of P was significantly lower compared to other groups (10% vs. 65%, respectively). Fish fed with diet A displayed lower whole-body ash and P content compared to other groups (1.98 vs. 2.49% and 035 vs. 0.46% wet weight, respectively). Phosphorus retention decreased with increasing dietary P level (from 100% in group A to about 20% in group E). The quantitative image analysis of 28-day-old fry double stained with Alcian blue and Alizarin red S revealed that individuals from group A were less ossified compared to individuals from other dietary groups. Quantitative analysis of skeletal formation using cumulative counts of endochondral and dermal structures revealed a significant delay in ossification of endochondral structures at day 11 in fish fed with mineral rich or poor diets (diets A, E and F). However, at day,28, no significant difference in ontogeny of endochondral or dermal structures was found between the trout fed with the control diet and those fed with a high P diet (E) ora low Ca diet (F), suggesting recovery is possible in rainbow trout. In conclusion, we found that both dietary deficiency and excess of P are detrimental to rainbow trout fry development: excess P affects survival, while P deficiency affects bone calcification. Calcium deficiency appears to exert some delay in ossification processes without affecting final bone mineralization. (c) 2009 Elsevier B.V. All rights reserved.

Domestic stocks may endanger wild populations by escapes or deliberate releases, not only through competition for resources but also through gene pool contamination if they reproduce in the wild. One of the risks is increased interspecific hybridization by interspecific matings. Stocking of domesticated genomes into wild ecosystems leads to a heightened frequency of interspecific hybridization in sympatric south European Atlantic salmon Salmo salar and brown trout Salmo trutta. Introgressive hybridization involving brown trout males of domestic origin was demonstrated. Following cessation of domestic stock releases in eight south European rivers, hybridization decreased significantly. These results emphasize the risks associated with stock transfers and escapes of domestic individuals in wild ecosystems and illustrate the potential role of domestic stocks when they contribute to secondary contact between species.

International audience; The objective of the present study was to identify postprandial molecular events associated with dietary fish oil level in rainbow trout using trout cDNA microarray tools (9 K). Our genomics data showed that relatively few hepatic genes (n=41) are differentially expressed between fish fed a high fat diet compared to those fed a diet without added fish oil. We then focus our analysis of specific events involved in intermediary metabolism by analysing them using qRT-PCR. Removal of fish oil was associated with higher lipid biosynthesis (reflected by the fatty acid synthase gene) and lower lipid catabolism (reflected by the acyl-CoA oxidase gene). More interestingly, some genes involved in proteasomal-dependant proteolysis (proteasome and ubiquitin ligase genes) were down regulated in fish fed without fish oil, suggesting a relationship between dietary lipid intake and regulation of hepatic protein metabolism in rainbow trout. (c) 2008 Elsevier B.V. All rights reserved.

International audience; Rainbow trout is unable to utilize high levels of dietary carbohydrates and experiences hyperglycemia after consumption of carbohydrate-rich meals. Carbohydrates stimulate hepatic glycolytic activity, but gene expression of the rate-limiting gluconeogenic enzymes glucose-6-phosphatase (G6Pase), fructose-1,6-bisphosphatase (FBPase) and phosphoenolpyruvate carboxykinase (PEPCK) remains high. Although there is significant mRNA expression and activity of gluconeogenic enzymes in trout intestine and kidney, the regulation of these enzymes by diet is not known. We tested the hypothesis that dietary carbohydrate modulates intestinal and renal G6Pase, FBPase and PEPCK. Fish were either fasted or fed isocaloric carbohydrate-free (CF) or high carbohydrate (HC) diets for 14 days. As expected, fish fed HC exhibited postprandial hyperglycemia and enhanced levels of hepatic glucokinase mRNA and activity. Dietary carbohydrates had no significant effect on the expression and activity of PEPCK, FBPase and G6Pase in all three organs. In contrast, fasting enhanced the activity, but not the mRNA expression of both hepatic and intestinal PEPCK, as well as intestinal FBPase. Therefore, the activity of rate-limiting gluconeogenic enzymes in trout can be modified by fasting, but not by the carbohydrate content of the diet, potentially causing hyperglycemia when fed high levels of dietary carbohydrates. In this species consuming low carbohydrate diets at infrequent intervals in the wild, fasting-induced increases in hepatic and intestinal gluconeogenic enzyme activities may be a key adaptation to prevent perturbations in blood glucose during food deprivation.

INRA UMR Ecobiop Saint Pée sur Nivelle - Localisation bibliothèque M 2132

In vertebrates there is a surprising diversity of sex determining systems. Here we show that a gene that was right now only known for its implication in the immune response, is a master sex determining gene conserved in salmonids.

Interspecific relationships between Atlantic salmon and coho salmon were studied at early life stages in laboratory and semi-natural stream channels. During emergence, the survival and dispersal patterns were similar for the two species in single or mixed populations. Survival of Atlantic salmon fry was reduced in the presence of older coho fry. However, no predation was observed. Microdistribution differed between the two species, with Atlantic salmon fry more numerous in riffles when coho were present. Coho juveniles had a pelagic and gregarious distribution, in contrast to the benthic behaviour of the Atlantic salmon. In laboratory streams, Atlantic salmon fry moved out or adopted a subordinate cryptic behaviour which allowed them to escape predation while negatively affecting their growth.

Master

SUMMARY Myostatin (GDF8) has been shown to be a major genetic determinant of skeletal muscle growth in mammals. In this study, we report the cloning of two trout cDNAs that encode two distinct myostatin-related proteins. The presence in this fish species of two myostatin genes (Tmyostatin 1 and Tmyostatin 2) probably results from the recent tetraploïdisation of the salmonid genome. A comparative reverse-transcriptase-linked polymerase chain reaction assay revealed that Tmyostatin 1 mRNA was present ubiquitously in trout tissues, while Tmyostatin 2 mRNA expression was restricted to muscle and brain. In developing muscle, Tmyostatin 1 expression was observed in eyed-stage embryos well before hatching, whereas Tmyostatin 2 was expressed only in free-swimming larvae. In myotomal muscle from adult animals, Tmyostatin 1 mRNA accumulation was similar in both slow- and fast-twitch fibres, and its concentration did not change during the muscle wasting associated with sexual maturation. In contrast, Tmyostatin 2 mRNA accumulated predominantly in slow-twitch fibres, and its concentration decreased dramatically in wasting muscles from maturing animals. This work shows that two distinct myostatin genes are present in the trout genome. Furthermore, it indicates that these two trout myostatin genes (i) exhibit a distinct expression pattern in muscle and non-muscle tissues and (ii) are not upregulated during the muscle wasting that accompanies sexual maturation.

One of the most recently identified members of the tumor necrosis factor receptor family, death receptor-6 (DR6), has been shown to mediate apoptosis following overexpression in HeLa cells. The avian and piscine orthologs of DR6 have now been identified, and the deduced amino acid sequence for each demonstrates a high level of conservation compared to the mammalian sequence. Expression of dr6 mRNA occurs widely across tissues of both the mature chicken and brook trout. It is now well-established that ovarian follicular atresia occurs via apoptosis originating within the granulosa cell layer. Accordingly, DR6 expression within the ovary was examined to assess the relationship between stage of follicle development and relative levels of this death receptor. Of particular interest was the finding that elevated levels of dr6 mRNA, as well as the translated protein, are expressed in atretic compared to healthy follicles of the hen ovary, thus providing the first association between DR6 expression and apoptosis, in vivo. We conclude that DR6 is a highly conserved and widely expressed death-domain-containing receptor and may be implicated in regulating follicle atresia within the vertebrate ovary.

The effects of independently altering chloride, calcium, and dissolved organic carbon (DOC) on the toxicity of silver were compared between rainbow trout (Oncorhynchus mykiss) and fathead minnows (Pimephales promelas). The 96-h median lethal concentration toxicity tests for both species were performed under the same conditions, within the same containers. In addition, the effect of altering [Cl{sup {minus}}] on silver-induced perturbations to body Na{sup +} influx and gill silver load was studied. Toxicity tests were conducted in synthetic soft water (50 {micro}M Na{sup +}, 50 {micro}M Cl{sup {minus}}, 50 {micro}M Ca{sup 2+}, 0.3 mg DOC/L). The [Cl{sup {minus}}], [Ca{sup 2+}], and [DOC] were adjusted by the addition of NaCl, CaNO{sub 3}, or humic acid, respectively. On the basis of total silver, increasing [Cl{sup {minus}}] over a range of 50 {micro}M to 1,500 {micro}M resulted in a 4.3-fold increase in the 96-h LC50 values (decrease in toxicity) for rainbow trout, but did not significantly affect the 96-h LC50 values for fathead minnows. Increasing water [Ca{sup 2+}] (from 50 to 2,000 {micro}M) had only a small influence on the 96-h LC50 values in both species. If the 96-h LC50 values are calculated on the basis of ionic silver, Ag{sup +}, then, in themore » case of rainbow trout, toxicity correlates to Ag{sup +}. However, this correlation does not exist for fathead minnows. Increasing [Cl{sup {minus}}] did not affect the degree of perturbation of Na{sup +} influx during acute exposure (first 4 h) to 8 {micro}g Ag/L in either species, nor did it affect the whole-body silver uptake rates, but it did reduce the gill silver load. These results demonstrate that differences exist in the way in which water chemistry ameliorates silver toxicity between rainbow trout and fathead minnows.« less

National audience; The effects of fines and water quality on incubating salmonid embryos were studied in two tributaries of the river Oir (Normandy, France) with different fish populations. Brown trout are very abundant in la Roche stream and their density is low in le Moulinet stream. We collected suspended and deposited sediments circulating within and sealing the substrate of two reproductive areas every 8 to 15 days in 1996 and 1997. Incubators were buried in the streambed to estimate the survival from egg to fry in 1996, and from fertilization to hatching and from hatching to emergence in 1997. The characteristics of the interstitial water (oxygen, pH, nitrates, nitrites and ammonia) were measured once a week in 1997. This was performed with sampling tubes buried in the substratum and with a sample collected in each incubator at hatching time. Preliminary results indicated that the amount of sediment in the spawning area was higher in la Roche stream during the incubation period. The particle size distribution was mainly sandy while it was silty in le Moulinet stream. No survivors were collected in fry traps at emergence in 1996 and between 0 and 11 % (mean : 3.3 %) were found in 1997 in le Moulinet stream. The survival in one fry trap was 20 % in 1996 in la Roche stream, between 0 and 23 % in 1997 (mean : 7.7 %).The hatching-to-emergence survival was high in the two rivers (83.6 and 82.3 %), with no rain falling during this period. Dissolved oxygen concentration of the interstitial water was significantly lower in le Moulinet stream (P = 0.01) during the second part of the incubation period while it remained quite high in la Roche stream (minimum value of 5 mg/l). Nitrate concentration is significantly different from that in the surface water (P = 0.01) in le Moulinet stream and equivalent in la Roche stream. Concentrations of nitrites and ammonia were low in the interstitial water of the two streams (maximum values : 12.9 µg/l N-NO2 and 240 µg/l N-NH3 in le Moulinet stream, 11.4 µg/l N-NO2 and 1.4 µg/l N-NH3 in la Roche stream). The higher mortalities observed in le Moulinet stream could be caused by a synergism of unfavourable factors such as low concentrations of oxygen and nitrites.; L'impact chimique et physique de la sédimentation sur la survie d'oeufs de Salmonidés a été étudié dans la partie amont de deux ruisseaux d'un même bassin à production salmonicole contrastée : le Moulinet qui présente une faible population de truites et la Roche qui est un ruisseau très productif. Les matières en suspension et les sédiments déposés ont été collectés à un pas de temps de 8 ou 15 jours en 1996 et 1997 et les survies embryo-larvaires ont été estimées en parallèle, dans des incubateurs artificiels. Les taux de survie ont été déterminés à l'émergence en 1996 et de la fécondation à l'éclosion, puis de l'éclosion à l'émergence en 1997. Les paramètres chimiques de l'eau interstitielle (oxygène, pH, nitrates, nitrites et ammoniac) ont été mesurés au pas de temps de la semaine pendant la période d'incubation 1997 sur des dispositifs enfouis dans le substrat du ruisseau et au moment de l'éclosion dans les incubateurs contenant les oeufs. Les premiers résultats montrent que les taux de survie embryo-larvaires sont nuls en 1996 et faibles en 1997 (0 à 11 %, moyenne : 3,3 %) dans le ruisseau du Moulinet alors que parallèlement, la survie est de 20 % sur un incubateur en 1996 et varie de 0 à 23 % en 1997 (moyenne : 7,7 %) dans le ruisseau de la Roche. De l'éclosion à l'émergence, les survies sont supérieures à 80 % dans les deux ruisseaux. La sédimentation est contrastée sur les deux sites, plus forte en masse dans le ruisseau de la Roche pendant la période d'incubation mais de granulométrie beaucoup plus grossière que dans le ruisseau du Moulinet (sableuse dominante contre argilolimoneuse). Les teneurs en oxygène dissous mesurées dans le substrat de la Roche restent élevées pendant toute la période d'incubation (teneur minimum de 5 mg/l) et sont significativement supérieures à celles mesurées dans le ruisseau du Moulinet pendant la deuxième partie de l'incubation 1997. D'autre part, les teneurs en nitrates sont équivalentes à celles de l'eau de surface pour la Roche alors qu'elles sont significativement différentes de l'eau de surface pour le Moulinet. Les concentrations en nitrites et ammoniac recensées sont au maximum de 12,9 µg/l de N-NO2 et 2 µg/l de N-NH4 sur le Moulinet et de 11,4 µg/l de N-NO2 et 1,4 µg/l de N-NH4 pour la Roche. Les mortalités plus élevées sur le site du Moulinet pourraient être dues à une synergie de facteurs défavorables présents dans le milieu tels que la présence de faibles teneurs en oxygène et de nitrites, comme cela a été reporté dans la littérature pour des poissons adultes.

Extensive asynchrony of sexual maturation is characteristic of salmonid females, and, for various reasons, the spawning season can be extended for 4 months, although it generally extends over a 3 week to 2 month period, as in brook trout and northern whitefish. In aquaculture, to ensure high fertilization and egg survival rates, it is recommended that identification of ovulating females be undertaken at least twice weekly. This is time-consuming when keeping large numbers of broodstock with an extended spawning season, and risk of stress damage to fish increases. Ensuring sufficient Arctic grayling broodstock relies on capture of wild animals from natural waters before onset of the spawning season. Capture and long-term holding of wild stocks is associated with high pre-spawning mortality. Due to the high ovulation synchronizing effect, GnRHa is practical for induction of ovulation 1?1.5 months prior to the natural spawning season. This work focused on optimization of methods of hormone-controlled reproduction using GnRHa in brook trout, northern whitefish, and Arctic grayling from Siberia. Because this is the first report of use of GnRHa in these species, emphasis was on optimization of the hormone dose and delivery method along with assessment of effects of GnRHa treatment on postspawning broodstock mortality, egg size, and egg viability. As in other salmonids, GnRHa treatment effectively synchronizes the onset of ovulation in brook trout and northern whitefish. This gives accurate information about ovulatory status of the broodstock and enables planning of the stripping schedule. The most convenient methods were the double acute injection at 25 ?g.kg-1 ?-Arg6,Pro9-NHEt-sGnRHa administered 3 days apart and injection of 25 ?g.kg-1 of emulsified ?-Arg6,Pro9-NHEt-sGnRHa in Freund´s incomplete adjuvant, which prolongs and more effectively stimulates LH secretion and requires only a single injection. Double acute injection at 10 ?g.kg-1 of ?-Tle6,Pro9-NHEt-mGnRHa (Supergestran) was sufficient to induce ovulation in Arctic grayling 1?1.5 months prior to natural spawning, and enabled accelerated stripping and return of wild broodstock to their natural habitat. Single acute injection proved to be ineffective or unreliable in most cases and therefore cannot be recommended. No negative effect of GnRHa or GnRHa-FIA treatments on post-spawning mortality of broodstock was observed. It has to be noted that that to the extent of law Nr. 166/1999 statute book (Czech veterinary law)injective procedures can be carried out just by the veterinarian or by a verinarian-authorized person in veterinarian presence. GnRHa treatment has side-effects and alters egg quality. Apart from in brook trout, egg survival was significantly lower (5?20%) in treated females. Increased hormone dose did not influence egg survival at the levels tested. Egg and hatchling size was lower in treated females compared to untreated specimens irrespective of dose or hormone delivery method. Reduced egg size is, however, not the likely source of reduced viability. In general, our results corroborate results of studies dealing with assessment of effects of hormone treatment on egg quality. Based on current experimental designs it is impossible to identify the cause of the side-effects with certainty. Solving this problem should be priority for future research.

Brown trout, with indwelling dorsal aortic cannulae, were exposed to various concentrations of aluminium (Al; 50 micrograms liter-1, 100% mortality over 48 hr; 25 micrograms liter-1, 50% mortality over 120 hr; 12.5 micrograms liter-1, 0% mortality over 120 hr) in acidic (pH 5.0) soft water. The plasma concentrations of prolactin (PRL), cortisol, thyroxine (T4), and triiodothyronine (T3) were monitored. Plasma PRL concentrations were transiently depressed (to less than 20% of resting concentrations) after 12 hr in trout in the two highest water Al concentrations, but were unchanged in the trout exposed to 12.5 micrograms liter-1 Al. Plasma cortisol concentrations were elevated in response to all water Al levels and remained elevated in trout in the lethal conditions. The sublethally exposed trout showed a recovery in plasma cortisol concentrations by 120 hr. Plasma T4 concentrations were significantly elevated in trout exposed to both the lethal and the sublethal Al concentrations (from mean resting concentrations of 1-2 ng ml-1 to peaks of 8.9 and 9.0 ng ml-1 in the 50 and 12.5 micrograms liter-1 Al groups, respectively), although a recovery in plasma concentrations was evident in the sublethally exposed trout from 72 hr onwards. Plasma T3 concentrations were relatively stable in the trout exposed to the two highest doses of Al, whereas the trout under the lowest, sublethal, Al conditions exhibited a sustained (12-72 hr) elevation in plasma T3 concentrations (from a mean resting concentration of 0.9 ng ml-1 to a peak of 4.2 ng ml-1 at 48 hr). No clear relationship was apparent between the plasma PRL concentrations and the previously reported ionoregulatory status of the trout.

International audience

In the study, the inhibitory effect of flavonoids, including isoflavonic phytoestrogens, on the ovarian aromatase enzyme complex from the rainbow trout, Oncorhynchus mykiss, was assessed in vitro. Some of the compounds tested on fish were also tested on human placental aromatase activity as a comparison between the two sources of enzyme. It was found that flavone, dl-aminoglutethimide, apigenin, quercetin, 7,4'- dihydroxyflavone, alpha-naphthoflavone and equol were potent inhibitors of the ovarian aromatase activity in rainbow trout. Relative potencies (RP) of these compounds compared to flavone (assigned an effect of 1) were, respectively, 19.0, 8.7, 5.3, 3.7, 3.2 and 0.9. Two other phytoestrogens, namely biochanin A and genistein, slightly inhibited aromatase activity. Finally, 7-hydroxyflavone, formononetin, daidzein, coumestrol, chrysin, flavanone and estradiol-17beta did not inhibit ovarian aromatase activity at doses up to 1000 microM. Experiments on human placental aromatase showed inhibitory effects of dl-aminoglutethimide, flavone, flavanone and equol with RP values of 2.8. 1, 1.5 and 0.4, respectively. These results are in accordance with previous studies. The influence of the experimental procedure on IC50 values and RP is discussed.

Des ovules de truites Arc-en-Ciel ont été fécondés par des spermatozoïdes de la même espèce traités par l'iode suivant différents protocoles afin de couper la transmission de la nécrose pancréatique infectieuse (NPI) des salmonidés. L'efficacité de l'iode a été évaluée en parallèle par neutralisation du virus en 1 mn. Le protocole conseillé pour la solution d'iode disponible dans le commerce (ovules égouttés, puis recouverts de solution- iodée et sperme ajouté immédiatement) a d'abord été utilisé. A pH compris entre 5 et 8 et pour des concentrations en iode de 15, 25 et 35 mg/l, le pourcentage de fécondation est inférieur à 10 et ne remonte qu'à pH 9 (69 % pour 25 mg/l). Par contre, l'efficacité contre le virus décroît rapidement pour des pH supérieurs à 7, et aucun pH n'a permis de concilier efficacité et innocuité. Le même protocole'utilisé avec 10 spermes individuels a montré des différences de sensibilité individuelle marquées (pourcentages de fécondation de 1,6 à 37 % pour 25 mg/l d'iode à pH8), qui ne sont pas en corrélation avec la qualité des spermes appréciée par la concentration de la protéine de membrane 42 kDa dans le liquide séminal. Les différents essais de préincubation du sperme (de quelques secondes à 1 minute) ont donné des rendements de fécondation nuls, sauf pour un large excès de sperme, qui entraînait aussi la perte de l'efficacité de l'iode contre le virus. Deux expériences de transmission expérimentale ont été réalisées en incubant les spermatozoïdes avec du virus concentré. L'élimination systématique des oeufs morts et anormaux suivie d'une désinfection externe des oeufs (50 mg/l d'iode, 15 mn) avant l'éclosion n'a pas permis dé couper la transmission, ce qui laisse supposer que le virus peut être transmis sans infecter l'embryon de façon létale.

We report the cloning of a new trout myogenic cDNA which encodes helix-loop-helix protein homologous to the myogenic factor myogenin. Northern analyses indicate that trout myogenin (Tmyogenin) transcripts accumulate in large amounts in the myotomal masculature of embryos and frys. In adults, transcripts concentrate within the thin lateral layer of red (slow oxydative) muscle fibres. They are present only in low amounts in white (fast glycolytic) muscle fibres which constitute the major part of the trunk musculature. Using an in vitro myogenesis system, we observed that the trout myogenin encoding gene is not activated until myosatellite cells fuse to generate multinucleated myotubes, indicating that Tmyogenin lies downstream of muscle determination factors. All these observations show that in a major taxinomic group like teleosts, a gene with homology to myogenin exists. Its activation during myogenesis suggests that it acts as a major developmental regulator of muscle differentiation.

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Session 2 : Diversité, écologie, conservation ; National audience

National audience

International audience

International audience

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SUMMARY This study was designed to assess the effects of dietary fat levels on glucose homeostasis in rainbow trout under prolonged hyperglycaemia induced by high carbohydrate intake. Trout were fed identical amounts of one of two iso-energetic diets containing either a low (LFD, 3%) or a high fat level (HFD, 20%) and similar amounts of digestible carbohydrates (26–30%) for 14 days. While a single high fat meal reduced glycaemia compared with a low fat meal, the consumption of a high fat diet for 14 days resulted in prolonged hypergylcaemia and reduced plasma glucose clearance in response to an exogenous glucose or insulin challenge. The hyperglycaemic phenotype in trout was characterised by a reduction of the activities of lipogenic and glucose phosphorylating enzymes with a concomitant stimulation of enzymes involved in glucose production in the liver and reduced glycogen levels in the white muscle. Impaired glucose tolerance (IGT) was further associated with a significant reduction of insulin receptor substrate 1 (IRS1) protein content in muscle, and with a poor response of HFD fed fish to an exogenous insulin load, suggestive of impaired insulin signalling in trout fed with a HFD. To our knowledge, this is the first study showing that a teleost can also develop a high fat-induced IGT, characterised by persistent hyperglycaemia and reduced insulin sensitivity, established symptoms of IGT and the prediabetic insulin-resistant state in mammals. Our results also provide evidence that persistent hyperglycaemia after a high carbohydrate meal stems from a metabolic interaction between dietary macronutrients rather than from high carbohydrate intake alone.

Glucose and lipid metabolism in pancreatic islet organs is poorly characterized. In the present study, using as a model the carnivorous rainbow trout, a glucose-intolerant fish, we assessed mRNA expression levels of several genes involved in glucose and lipid metabolism (including ATP-citrate lyase; carnitine palmitoyltransferase-1 isoforms, CPT; the mitochondrial isoform of the phosphoenolpyrutave carboxykinase, mPEPCK and pyruvate kinase, PK) and glucosensing (glucose transporter type 2, Glut2; glucokinase, GK and the potassium channel, K(ATP)) in Brockmann bodies. We evaluated the response of these parameters to changes in feeding status (food deprived vs. fed fish) as well as to changes in the amount of carbohydrate (dextrin) in the diet. A general inhibition of the glycolytic (including the glucosensing marker GK) and β-oxidation pathways was found when comparing fed versus food-deprived fish. When comparing fish feeding on either low- or high-carbohydrate diets, we found that some genes related to lipid metabolism were more controlled by the feeding status than by the carbohydrate content (fatty acid synthase, CPTs). Findings are discussed in the context of pancreatic regulation of glucose and lipid metabolism in fish, and show that while trout pancreatic metabolism can partially adapt to a high-carbohydrate diet, some of the molecular actors studied seem to be poorly regulated (K(ATP)) and may contribute to the glucose intolerance observed in this species when fed high-carbohydrate diets.

The objective of this study was to investigate the expression of two promyogenic cell surface adhesion receptors, N- and M-cadherin, in developing trout (Oncorhynchus mykiss) somite, taking account of the recent identification of a dermomyotome-like epithelium in teleosts. In situ hybridization showed that N-cadherin was expressed throughout the paraxial mesoderm and nascent somite. As the somite matured, N-cadherin expression disappeared ventrally from the sclerotome, and then mediolaterally from the differentiating slow and fast muscle cells of the embryonic myotome, to become finally restricted to the undifferentiated myogenic precursors forming the dermomyotome-like epithelium that surrounds the embryonic myotome. By contrast, M-cadherin, which was transcribed in the differentiating embryonic myotome, was never expressed in the dermomyotome-like epithelium. In late-stage trout embryos, M-cadherin transcript was only detected at the periphery of the expanding myotome, where muscle cells stemming from the N-cadherin positive dermomyotome-like epithelium differentiate. Collectively, our results support the view that, in trout embryo, N-cadherin is associated with muscle cell immaturity while M-cadherin is associated with muscle cell maturation and differentiation and this during the two successive phases of myogenesis. J. Exp. Zool. (Mol. Dev. Evol.) 318:71-77, 2012. (C) 2011 Wiley Periodicals, Inc.

International audience; In 1997 the Cle Elum Supplementation Research Facility was established to enhance spring Chinook salmon returning to the upper Yakima River, Washington State. This effort increased spring Chinook abundance, yet conditions at the hatchery also significantly elevated the occurrence of jacks and yearling precocious males. The potential genetic effect that a large influx of early maturing males might have on the upper Yakima River spring Chinook population was examined in an artificial stream. Seven independent groups of fish were placed into the stream from 2001 through 2005. Males with four different life history strategies, large anadromous, jacks, yearling precocious, and sub-yearling precocious were used. Their breeding success or ability to produce offspring was estimated by performing DNA-based pedigree assessments. Large anadromous males spawned with the most females and produced the greatest number of offspring per mate. Jacks and yearling precocious males spawned with more females than sub-yearling precocious males. However, jacks, yearling and sub-yearling precocious males obtained similar numbers of fry per mate. In the test groups, large anadromous males produced 89%, jacks 3%, yearling precocious 7%, and sub-yearling precocious 1% of the fry. These percentages remained stable even though the proportion of large anadromous males in the test groups ranged from 48% to 88% and tertiary sex ratios varied from 1.4 to 2.4 males per female. Our data suggest that large anadromous males generate most of the fry in natural settings when half or more of the males present on a spawning ground use this life history strategy

Many fish species experience long periods of fasting often associated with seasonal reductions in water temperature and prey availability or spawning migrations. During periods of nutrient restriction, changes in metabolism occur to provide cellular energy via catabolic processes. Muscle is particularly affected by prolonged fasting as proteins of this tissue act as a major energy source. However, the molecular components involved in muscle protein degradation as well as the regulatory networks that control their function are still incompletely defined in fish. The present work aimed to characterize the response of the autophagy-lysosomal degradative pathway to nutrient and serum availability in primary culture of rainbow trout myoblasts. In this aim, 4-day-old cells were incubated in a serum and amino acid-rich medium (complete medium), a serum and amino acid-deprived medium (minimal medium) or a minimal medium plus amino acids, and both the transcription-independent short-term response and the transcription-dependent long-term response of the autophagy-lysosomal degradative pathway were analyzed. We report that serum and amino acids withdrawal is accompanied by a rapid increase of autophagosome formation but also by a slower induction of the expression of several autophagy-related genes (LC3B, gabarapl1, atg4b). We also showed that this latter response is controlled by amino acid (AA) availability and that both TOR-dependent and TOR-independent pathways are involved in this effect. Together these results suggest an important role for AA released by muscle proteolysis during the fasting period in regulating the subtle balance between using proteins as disposable furniture to provide energy, and conserving muscle through protein sparing.

Predicting the persistence and adaptability of natural populations to climate change is a challenging task. Mechanistic models that integrate biological and evolutionary processes are helpful toward this aim. Atlantic salmon, Salmo salar (L.), is a good candidate to assess the effect of environmental change on a species with a complex life history through an integrative modelling approach due to (i) a large amount of knowledge concerning its biology and (ii) extensive historical data sets that can be used for model validation. This paper presents an individual-based demo-genetic model developed to simulate S. salar population dynamics in southern European populations: IBASAM (Individual-Based Atlantic SAlmon Model). The model structure is described thoroughly. A parameterization exercise was conducted to adjust the model to an extensive set of demographic data collected over 15 years on the Scorff River, Brittany, France. A sensitivity analysis showed that two parameters determining mean and variability of juvenile growth rates were crucial in structuring the simulated populations. Additionally, realistic microevolutionary patterns of different aspects of life history were predicted by the model, reproducing general knowledge on S. salar population biology. The integration into IBASAM of a demo-genetic structure coupled with the explicit representation of individual variability and complex life histories makes it a cohesive and novel tool to assess the effect of potential stressors on evolutionary demography of Atlantic salmon in further studies.