The sea bass Dicentrarchus labrax as a marine model species in immunology:Insights from basic and applied research

This review summarizes the current knowledge on immune defence activities of the European sea bass Dicentrarchus labrax by reporting the consistent amount of work done on this economically-important species.A draft genome sequence is available for this species,together with whole transcriptomes from lymphoid and non-lymphoid tissues.Available full-length coding sequences of many immunoregulatory and immune-related genes allow for targeted quantitative PCR analysis,nowadays needed for-omics data verification,ex vivo and in vitro.The first anti-T cells monoclonal antibody teleost-wise was obtained in sea bass,followed by several monoclonal and polyclonal markers of lymphocyte populations,namely T cells(pan-T,CD3ε,TcRγ,CD45),and B cells(IgM,IgT,IgD).The combined use of molecular and biochemical tools enabled investigations on innate and acquired immune responses of sea bass in unstimulated/stimulated fish,along the development and under variable environmental conditions and food regimes.An overview of sea bass viral and bacterial pathogens and available vaccines against these microorganisms is also provided.The knowledge accumulated in the past 25 years validates the European sea bass as a reference marine model in the field of fish immunology.

A plant-based diet supplemented with Hermetia illucens alone or in combination with poultry by-product meal:one step closer to sustainable aquafeeds for European seabass

Background:Increasing demand for high-value fish species and pressure on forage fish is challenging aquaculture to ensure sustainable growth by replacing protein sources in aquafeeds with plant and terrestrial animal proteins,without compromising the economic value and quality of the final fish product.In the present study,the effects of a plant protein-based diet(CV),two plant-based diets in which graded amounts of plan protein mixtures were replaced with Hermetia illucens meal alone(VH10)or in combination with poultry by-product meal(PBM)(VH10P30),a fishmeal(FM)diet(CF)and an FM diet supplemented with H.illucens(FH10)on growth performance,gut health and homeostasis of farmed subadult European seabass were tested and compared.Results:Fish fed the VH10 and VH10P30 diets showed the highest specific growth rates and lowest feed conversion ratios among the tested groups.Expectedly,the best preservation of PI morphology was observed in fish fed the CF or FH10 diets,while fish fed the CV diet exhibited significant degenerative changes in the proximal and distal intestines.However,PBM supplementation mitigated these effects and significantly improved all gut morphometric parameters in the VH10P30 group.Partial substitution of the plant mixture with insect meal alone or PBM also induced most BBM genes and activated BBM enzymes,suggesting a beneficial effect on intestinal digestive/absorption functions.Regarding intestinal microbiota,fish fed diets containing H.illucens meal(FH10,VH10,VH10P30)had the highest richness of bacterial communities and abundance of beneficial genera such as Lactobacillus and Bacillus.On the other hand,fish fed CV had the highest microbial diversity but lost a significant component of fish intestinal microbiota,the phylum Bacteroidetes.Finally,skin pigmentation most similar to that of farmed or even wild seabass was also observed in the fish groups fed CF,FH10 or VH10P30.Conclusion:Plant-based diets supplemented with PBM and H.illucens pupae meal have great potential as alternative diets for European seabass,without affecting growth performance,gut homeostasis,or overall fitness.This also highlights the importance of animal proteins in diets of European seabass,as the addition of a small amount of these alternative animal protein sources significantly improved all measured parameters.