Effects of the total replacement of fish-based diet with plant-based diet on the hepatic transcriptome of two European sea bass (Dicentrarchus labrax) half-sibfamilies showing different growth rates with the plant-based diet

Background: Efforts towards utilisation of diets without fish meal (FM) or fish oil (FO) in finfish aquaculture have been being made for more than two decades. Metabolic responses to substitution of fishery products have been shown to impact growth performance and immune system of fish as well as their subsequent nutritional value, particularly in marine fish species, which exhibit low capacity for biosynthesis of long-chain poly-unsaturated fatty acids (LC-PUFA). The main objective of the present study was to analyse the effects of a plant-based diet on the hepatic transcriptome of European sea bass (Dicentrarchus labrax). Results: We report the first results obtained using a transcriptomic approach on the liver of two half-sibfamilies of the European sea bass that exhibit similar growth rates when fed a fish-based diet (FD), but significantly different growth rates when fed an all-plant diet (VD). Overall gene expression was analysed using oligo DNA microarrays (GPL9663). Statistical analysis identified 582 unique annotated genes differentially expressed between groups of fish fed the two diets, 199 genes regulated by genetic factors, and 72 genes that exhibited diet-family interactions. The expression of several genes involved in the LC-PUFA and cholesterol biosynthetic pathways was found to be up-regulated in fish fed VD, suggesting a stimulation of the lipogenic pathways. No significant diet-family interaction for the regulation of LC-PUFA biosynthesis pathways could be detected by microarray analysis. This result was in agreement with LC-PUFA profiles, which were found to be similar in the flesh of the two half-sibfamilies. In addition, the combination of our transcriptomic data with an analysis of plasmatic immune parameters revealed a stimulation of complement activity associated with an immunodeficiency in the fish fed VD, and different inflammatory status between the two half-sibfamilies. Biological processes related to protein catabolism, amino acid transaminations, RNA splicing and blood coagulation were also found to be regulated by diet, while the expression of genes involved in protein and ATP synthesis differed between the half-sibfamilies. Conclusions: Overall, the combined gene expression, compositional and biochemical studies demonstrated a large panel of metabolic and physiological effects induced by total substitution of both FM and FO in the diets of European sea bass and revealed physiological characteristics associated with the two half-sibfamilies

Caractérisation du nodavirus, pathogénie et épidémiologie expérimentale de la nodavirose ou de l'encéphalopathie et rétinopathie virales chez le bar juvénile "Dicentrarchus labrax L."

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Impact de pollutions chimiques chroniques (hydrocarbures, pesticides) sur l'état sanitaire et le système immunitaire du poisson

L'écotoxicité des hydrocarbures et des pesticides, a été recherchée chez le poisson adulte à des concentrations d'exposition in vivo correspondant à celles retrouvées chroniquement in situ. Le statut sanitaire et l'état de santé ont été évalués chez le bar commun, Dicentrarchus labrax exposés à un mélange d'hydrocarbures via la fraction soluble d'un pétrole brut et chez la truite arc en ciel, Oncorhynchus mykiss contaminée à une substance active de pesticide, la pendiméthaline. Les molécules polluantes ont été quantifiées à la fois dans l'eau d'exposition et les poissons (muscles et bile), confirmant l'efficacité des systèmes expérimentaux utilisés. L'exposition chronique à ces polluants dégrade l'état sanitaire du poisson, augmentant le risque potentiel pour la santé du consommateur. De plus, l'état de santé du poisson évalué via le suivi de plusieurs paramètres physiologiques, biochimiques et immunologiques est perturbé. En effet, une leucopénie expliquée par une lymphopénie, ainsi qu'une diminution de l'activité phagocytaire sont systématiquement observées chez les poissons exposés aux xénobiotiques, affectant l'immunité adaptative et innée. Lors d'une épreuve infectieuse au virus de la septicémie hémorragique virale, la pendiméthaline entraîne une mortalité plus précoce des individus et un nombre de poissons séropositifs supérieur. Enfin, les impacts observés à des concentrations d'exposition inférieures aux concentrations sans effet prévisible (PNEC) estimées actuellement, soulignent l'intérêt de prendre en compte l'état sanitaire et les composants du système immunitaire des organismes aquatiques dans l'établissement de seuils de qualité environnementale.The ecotoxicity of hydrocarbons and pesticides, was investigated in adult fish at in vivo exposure concentrations similar to those found chronically in the natural environment. The sanitary status, i.e. the health status of fish, with regard to chemical pollution and physiological status, was evaluated in sea bass, Dicentrarchus labrax exposed to a mixture of hydrocarbons using the water soluble fraction of crude oil and in rainbow trout, Oncorhynchus mykiss, contaminated by an active substance present in pesticide, pendimethalin. The pollutant molecules were quantified both in the exposure water and the fish (muscle and bile), confirming the efficiency of the experimental systems used. Chronic exposure to these pollutants deteriorates sanitary status in fish, increasing the potential risk for the health of human consumers. In addition, the health of fish assessed by monitoring several physiological, biochemical and immunological parameters was shown to be disturbed. Indeed, leucopenia due to lymphopenia and a decrease in phagocytic activity were observed in fish whatever the experimental exposure conditions, affecting innate and adaptive immunity. Following the infectious challenge with the viral hemorrhagic septicemia virus, pendimethalin seemed to accelerate fish mortality and a high number of seropositive fish was recorded compared to the group of control fish. Finally, these effects were observed at exposure levels below the currently estimated predicted no-effect concentrations (PNEC), highlighting the importance of taking into account sanitary status and the components of the immune system in aquatic organisms when establishing environmental quality thresholds.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

La maladie du pancréas chez le saumon atlantique (Salmo salar L.) (pathogénie, réponse immunitaire et vaccination)

L'injection du virus de la maladie du pancréas (VMP) à des parrs de saumon atlantique provoque, au cours de la première semaine d'infection, une nécrose coagulative du pancréas exocrine, accompagnée d'une inflammation locale. Une phase cardiaque vient ensuite, au cours de la deuxième semaine, marquée par une nécrose des fibres musculaires du ventricule. Une virémie transitoire est également observée dans les premiers jours. L'ensemble du tableau lésionnel, ainsi que la charge virale dans le plasma, sont réduits en un mois. Ceci peut être rapproché de la stimulation du système immunitaire et notamment, de celle du lysozyme, du complément, de l'activité phagocytaire des leucocytes du rein antérieur mais surtout, des anticorps neutralisants. Le rôle protecteur de ces derniers est confirmé par des essais de transfert d'immunité humorale tandis que la transplantation de lymphocytes immuns suggère l'importance, outre des plasmocytes, des cellules cytotoxiques non spécifiques, ou CCN, dans la réponse anti-VMP. Lors d'essais de cytotoxicité in vitro par cytométrie en flux, ces CCN s'avèrent efficaces dans la destruction de cellules xénogéniques de poissons transformées, notamment lorsqu'elles sont infectées par le VMP. De plus, cette activité cytotoxique peut être stimulée pendant un mois par une infection in vivo par le VMP. Un vaccin injectable - à base de VMP inactivé, formulé dans une émulsion avec des bactéries tuées - est produit. Le modèle prévoit que 3 doses vaccinales soient éprouvées par 3 doses d'épreuve virulente. Seule la dose d'épreuve la plus forte conduit à des résultats interprétables et une réduction des lésions et de la virémie est obtenue avec l'ensemble des doses vaccinales testées. Cette protection, probablement liée aux anticorps neutralisants ainsi qu'à l'action non spécifique de l'adjuvant, n'est cependant que partielle. De nouveaux adjuvants vaccinaux sont ensuite testés. Parmi ces derniers, les ODN CpG induisent une bonne protection des tissus face au VMP, sous l'effet probable de cytokines et d'une immunité cellulaire, mais ils semblent n'entraîner qu'une faible réponse humorale spécifique. Les bactéries tuées confirment, quant à elles, leur effet protecteur non spécifique tant sur les lésions que sur la charge virale. Enfin, les liposomes n'apparaissent pas comme des transporteurs au adjuvats vaccinaux efficaces pour ce type de vaccin.BREST-BU Droit-Sciences-Sports (290192103) / SudocSudocFranceF

Effects of dietary oxidized fish oil and antioxidant deficiency on histopathology, haematology, tissue and plasma biochemistry of sea bass

Two groups of sea bass (mean initial weight 78 and 250 g) were given for 23 weeks a commercial diet, whose composition was modified or not (control). The modified diet was: — supplemented with highly oxidized fish oil, — poorly supplemented with ascorbic acid, — not supplemented with butylated hydroxytoluene, DL-alpha-tocopheryl acetate and choline. At the end of the experiment, fish fed the modified diet displayed skeletal muscle degeneration, decreased red blood cell count, haemoglobin content and haematocrit, and increased crythrocyte fragility and plasma enzyme activity (aspartate aminotransferase and creatine kinase). Simultaneously, low DL-alpha-tocopheryl acetate levels and increased amounts of thiobarbituric acid-reactive substances were observed in muscle and liver. On the other hand, growth disorders, liver lesions, changed plasma enzyme activity (alanine aminotransferase, glutathione peroxydase), or altered conjugated dienes in perivisceral fat were not evidenced. The pathological observations were more pronounced on the smaller fish group, but the disease could already be detected by measuring haematological and biochemical criteria, the interest of which in the diagnosis of such nutritional disease is discussed

Toxicological effects of dispersed crude oil on Golden Mullet Liza aurata innate immune function

Dispersants transfer oil from the water surface into the water column and consequently modify hydrocarbons petroleum fish uptake. It appears that toxicity will depend on whether oil dispersion increases or decreases the exposure of aquatic species to the toxic components of oil. Lethal bioassays were conducted on Liza aurata. During 48 h, fish were exposed under several pathways of oil contamination: water soluble fraction of oil (WSF), a chemically dispersed crude oil and a mechanically dispersed crude oil. In addition, a control condition with dispersant was evaluated. Hydrocarbons concentrations were determined along the exposure period (on their soluble and particular fraction). Following this period, a 14 days recovery period was conducted. Because understanding changes in fish immune system is relevant for evaluating the health of the aquatic environment, our study deals with modification of its response by recognised biomarkers such as the haemolytic activity of alternative complement pathway (ACH50). In addition, we studied gill surface and hepatic morphological histology to better understand the innate immunity alteration. Furthermore, physiological parameters including condition factor and liver somatic index, biotransformation enzymes such as 7-ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase, antioxidant enzymes including glutathione peroxidase and total glutathione (GSH) content and lipoperoxidation (as TBARS) were measured in these conditions. These responses were correlated to the exposure level by bioaccumulation measurements before and after the decontamination period

In vivo effects of LCO soluble fraction on immune-related functions and gene transcription in the Pacific oyster, Crassostrea gigas (Thunberg)

International audienceThe effects of a soluble fraction of light cycle oil (LCO) on haemocyte parameters, phenoloxidase (PO) activity and mRNA expression of immune-related genes, in the Pacific oyster, Crassostrea gigas, were tested after seven days of exposure and two weeks of recovery period. Five polycyclic aromatic hydrocarbons (PAHs) out of ten detected in tank water had bioaccumulated at the end of the contamination period. The concentration of PAHs in oyster tissues decreased during the recovery period and 14 days after the exposure, 69% of bioaccumulated PAHs were detected in contaminated oysters. The exposure induced severe oyster mortality (21%), external and internal green colouration of the shell and a significant decrease of PO activity. The mRNA expression of several genes was altered. As a conclusion, a modulation of immune-related parameters was demonstrated using three different approaches, namely cellular (flow cytometry), biochemical (spectrophotometry) and genomics (gene transcription) in oysters after contact with soluble fraction of LCO

Immune effects of HFO on European sea bass, Dicentrarchus labrax, and Pacific oyster, Crassostrea gigas

International audienceThe European sea bass, Dicentrarchus labrax, and the Pacific oyster, Crassostrea gigas, were exposed to a soluble fraction of heavy fuel oil for 5 and 9 days, respectively. The organisms were then transferred to non-contaminated seawater for 1 month. The bioaccumulation and elimination of PAHs in contaminated tissues were dissimilar between species. In fish, acenaphthene and naphthalene were detected and naphthalene was still detectable 30 days after the beginning of the recovery period. In oysters, on the other hand, pyrene and phenanthrene were bioaccumulated and 14 days after exposure no more PAHs were detected. Concerning innate immune parameters, the increase of haemolytic activity of the alternative complement pathway in fish and the reduction of phenoloxidase activity in oysters endured, respectively, 1 and 2 weeks in contaminated organisms. This indicates that these two enzymatic cascades could be quite useful for monitoring pollution by oil