Ecloserie Marine de Gravelines

Gravelines, France

Ecloserie Marine de Gravelines

Gravelines, France
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Yaacob E.N.,Ghent University | Yaacob E.N.,University of Malaysia, Terengganu | Goethals J.,Ghent University | Bajek A.,Ecloserie Marine de Gravelines | And 4 more authors.
Marine Biotechnology | Year: 2017

Aquaculture is the fastest growing animal production sector. However, the production of marine fish is still hampered by the high mortality rate in the first few weeks after hatching. Mortality in larvae is often caused by microbial infections. Today, the incorporation of immunostimulants into microparticles provides us new tools to enhance disease resistance in marine larviculture. In this study, we prepared alginate microparticles loaded with the model antigen fluorescein isothiocyanate conjugated-bovine serum albumin. Optimum concentrations of alginate and CaCl2, the correct alginate viscosity and the appropriate preparatory conditions led to the creation of desirable microparticles with the correct size for oral feeding in gnotobiotic European sea bass larvae. The prepared alginate microparticles were stable in sea water and were successfully ingested by gnotobiotic sea bass larvae at day after hatching 7 without causing any negative effects. Results suggest the suitability of this drug delivery system for targeting the innate immune system of fish larvae in order to enhance disease resistance and thus reduce mortality in larviculture. © 2017 Springer Science+Business Media, LLC

Schaeck M.,Ghent University | Duchateau L.,Ghent University | Van den Broeck W.,Ghent University | Van Trappen S.,Ghent University | And 5 more authors.
Veterinary Microbiology | Year: 2016

Due to the mounting awareness of the risks associated with the use of antibiotics in aquaculture, treatment with probiotics has recently emerged as the preferred environmental-friendly prophylactic approach in marine larviculture. However, the presence of unknown and variable microbiota in fish larvae makes it impossible to disentangle the efficacy of treatment with probiotics. In this respect, the recent development of a germ-free culture model for European sea bass (Dicentrarchus labrax L.) larvae opened the door for more controlled studies on the use of probiotics.In the present study, 206 bacterial isolates, retrieved from sea bass larvae and adults, were screened in vitro for haemolytic activity, bile tolerance and antagonistic activity against six sea bass pathogens. Subsequently, the harmlessness and the protective effect of the putative probiotic candidates against the sea bass pathogen Vibrio harveyi were evaluated in vivo adopting the previously developed germ-free sea bass larval model.An equivalence trial clearly showed that no harmful effect on larval survival was elicited by all three selected probiotic candidates: Bacillus sp. LT3, Vibrio lentus and Vibrio proteolyticus. Survival of Vibrio harveyi challenged larvae treated with V. lentus was superior in comparison with the untreated challenged group, whereas this was not the case for the larvae supplemented with Bacillus sp. LT3 and V. proteolyticus. In this respect, our results unmistakably revealed the protective effect of V. lentus against vibriosis caused by V. harveyi in gnotobiotic sea bass larvae, rendering this study the first in its kind. © 2016.

Rekecki A.,Ghent University | Gunasekara R.A.Y.S.A.,Ghent University | Dierckens K.,Ghent University | Laureau S.,Ecloserie Marine de Gravelines | And 7 more authors.
Journal of Fish Diseases | Year: 2012

The location and cell damage caused by Vibrio anguillarum, the causative agent of classical vibriosis, within the developing gut of the newly hatched sea bass, Dicentrarchus labrax (L.), is unknown. A gnotobiotic sea bass model was used to investigate the early interactions of V. anguillarum with sea bass larvae. In the present study, germ-free sea bass larvae were orally exposed to a V. anguillarum HI-610 pathogen labelled with the green fluorescent protein (GFP-HI-610) and sampled at regular intervals. Pathogenic colonization of gut enterocytes was observed 2h post-exposure (p.e.) and onwards, whereas bacteria within the swim bladder were visualized 48h p.e and onwards. Ultrastructural findings demonstrated direct bacterial contact with the host cell in the oesophageal mucosa and putative attachment to microvilli of mid- and hindgut enterocytes. The present findings form a starting point for studies assessing the impact of potential candidates (probiotics, prebiotics, antimicrobial peptides) to mitigate bacterial virulence. © 2012 Blackwell Publishing Ltd.

Yaacob E.N.,Ghent University | Yaacob E.N.,University of Malaysia, Terengganu | Vandenbosch D.,Ghent University | Coenye T.,Ghent University | And 4 more authors.
Aquaculture | Year: 2016

Marine fish larvae are known to drink water and to feed selectively. We studied water and microparticle ingestion of axenic sea bass larvae at the early post-hatching stage. Knowledge on these physiological processes is crucial for designing effective feeding, particle delivery schemes for marine fish larvae and for the understanding of the interaction and/or association between larval fish and smaller microparticles such as bacteria in aquaculture systems. We found that the fluorescence intensity of accumulated FITC-labelled dextran in the gut of laboratory-reared axenic European sea bass larvae (Dicentrarchus labrax), at day after hatching 7 (DAH7), correlated to a drinking rate of 4.1 ± 0.1 nL h-1 larva-1. Additionally, by providing microparticles of 2, 10 or 45 μm, each time in combination with reference microparticles of 20 μm at an equal particle volume, feed size selection was examined. Feeding bigger particles (a combination of 45 and 20 μm) resulted in a statistically higher mean ingested volume (105 ± 104 μm3 larva-1) than feeding particle combinations of 2 and 20 μm or 10 and 20 μm, (104 ± 103 μm3 larva-1). Based on Jacobs' selectivity index (D-values), fish larvae always selected for the bigger particles. In addition, larvae showed significantly positive selection towards 45 μm particles after 12 h of feeding. We conclude that axenic European sea bass larvae at DAH7 fed selectively on larger microparticles and unintentionally ingested small microparticles through drinking. Thus, both active and unintentional uptake of microparticles can be useful for microparticle delivery in early post-hatching marine fish larviculture. These results produce insight into the possibility of feeding with an appropriate particle size for future studies using early post-hatching axenic European sea bass larvae as model animal. Statement of relevance: Axenic European sea bass larvae exhibited drinking activity at DAH7 and our data from the particle size selection are relevant for the use in developing of an effective feeding and microparticles delivery schemes in sea bass larviculture. In addition, unintentional uptake of small sized particles could be useful in the application of beneficial probiotic bacteria through suspension feeding. © 2016 Elsevier B.V.

Li X.,Ghent University | Defoirdt T.,Ghent University | Yang Q.,Ghent University | Laureau S.,Ecloserie Marine de Gravelines | And 2 more authors.
Diseases of Aquatic Organisms | Year: 2014

Vibrio anguillarum is the major cause of haemorrhagic septicaemia, vibriosis, which is a severe disease affecting marine fish. In this work, it was found that the mortality of gnotobiotic sea bass larvae challenged with V. anguillarum was dependent on the number of dead fish in the vials at the moment of challenge. Based on this finding, the effect of dead hosts (homogenised sea bass larvae or brine shrimp) on the virulence of V. anguillarum towards sea bass larvae was further investigated. Addition of homogenised hosts led to significantly increased larval mortality of challenged larvae, and this was observed for 3 different V. anguillarum strains, i.e. 43, NB 10 and HI 610. In contrast, the addition of similar levels of tryptone had no effect on mortality. In line with this, the motility of all 3 V. anguillarum strains was significantly increased by the addition of homogenised hosts but not by tryptone. These results suggest that dead hosts increase infectivity of V. anguillarum, not merely by offering nutrients to the bacteria, but also by increasing virulence-associated activities such as motility. © Inter-Research 2014.

Schaeck M.,Ghent University | De Swaef E.,Ghent University | Van Den Broeck W.,Ghent University | Van Nevel S.,Ghent University | And 8 more authors.
Diseases of Aquatic Organisms | Year: 2016

A thorough understanding of host-microbe interactions is crucial for more efficient disease management in the marine larviculture industry. As demonstrated in terrestrial animal research, gnotobiotic systems (involving animals cultured in germ-free conditions or inoculated with known microorganisms) are excellent tools to extend our understanding of the mechanisms involved in host-microbe interactions and allow the evaluation of new treatments for diseases. In this study, we introduce a germ-free European sea bass Dicentrarchus labrax larval model, independent of the continuous addition of antimicrobial agents. This model has an experimental set-up that allows addition of live feed to the larvae without compromising the germ-free status. This model will facilitate and render aquaculture research more effective in terms of mitigation fish larval diseases. © 2016 Inter-Research.

Vandeputte M.,French Research Institute for Exploitation of the Sea | Vandeputte M.,French National Institute for Agricultural Research | Garouste R.,French Research Institute for Exploitation of the Sea | Dupont-Nivet M.,French National Institute for Agricultural Research | And 12 more authors.
Aquaculture | Year: 2014

Sea bass is a major species in Mediterranean aquaculture, but has a distribution area ranging from North Atlantic to South Mediterranean, with a population structure previously revealed by population genetics. To test the farming performances of wild sea bass populations, we produced a partial diallel cross mating scheme, using sires originating from North Atlantic (NAT), South Atlantic (SAT), West Mediterranean (WEM), North-East Mediterranean (NEM) and South-East Mediterranean (SEM). Fifteen sires per origin were mated in a full-factorial design using artificial fertilization with 9 NAT dams and 17 WEM dams, producing 10 population crosses and 1950 potential full-sib families. All fish were reared together, then tagged at an average weight of 20. g and distributed to four different sites (1800 fish per site). They were grown to an objective of 200. g mean weight, where 737 to 775 fish were slaughtered in each site, and their parentage was recovered using 6 to 7 microsatellite loci, resulting in 98.9% unique assignments. All populations had similar growth rates until tagging size (20. g), but differences appeared later on. No heterosis appeared for growth rate, and genotype by environment interaction (G × E) at the population level was limited, with a significant re-ranking only in one rearing site, while strong G × E for growth rate was observed within populations. Populations were different in shape, muscular fat content, and carcass yield, but not in fillet yield. In general, heterosis was absent and G × E was very limited between populations. No "ideal" population combining all favorable traits was identified. Differences between extreme populations ranged between 3 and 49% of the mean, depending on the traits. Interestingly, in almost all cases, these differences were within the reach of one generation of intense (5%) phenotypic selection. © 2014 Elsevier B.V.

Rekecki A.,Ghent University | Ringo E.,University of Tromsø | Olsen R.,University of Tromsø | Myklebust R.,University of Bergen | And 8 more authors.
Journal of Fish Diseases | Year: 2013

As adhesion and translocation through fish gut enterocytes of the pathogen Vibrio (Listonella) anguillarum are not well investigated, the effective cause of disease and mortality outbreaks in larval sea bass, Dicentrarchus labrax, suffering from vibriosis is unknown. We detected V. anguillarum within the gut of experimentally infected gnotobiotic sea bass larvae using transmission electron microscopy and immunogold labelling. Intact bacteria were observed in close contact with the apical brush border in the gut lumen. Enterocytes contained lysosomes positive for protein A-gold particles suggesting intracellular elimination of bacterial fragments. Shed intestinal cells were regularly visualized in the gut lumen in late stages of exposure. Some of the luminal cells showed invagination and putative engulfment of bacterial structures by pseudopod-like formations. The engulfed structures were positive for protein A-colloidal gold indicating that these structures were V. anguillarum. Immunogold positive thread-like structures secreted by V. anguillarum suggested the presence of outer membrane vesicles (MVs) hypothesizing that MVs are potent transporters of active virulence factors to sea bass gut cells suggestive for a substantial role in biofilm formation and pathogenesis. We put forward the hypothesis that MVs are important in the pathogenesis of V. anguillarum in sea bass larvae. © 2012 Blackwell Publishing Ltd.

Li X.,Ghent University | Bossier P.,Ghent University | Dierckens K.,Ghent University | Laureau S.,Ecloserie marine de Gravelines | Defoirdt T.,Ghent University
Veterinary Microbiology | Year: 2015

In this study, we investigated the impact of the host factors mucin, bile salts and cholesterol on the virulence of the economically important aquatic pathogen Vibrio anguillarum towards sea bass larvae. Pretreatment of V. anguillarum with either one of the host factors (at 10mgl-1) prior to inoculation into the sea bass rearing water increased virulence of the bacterium, although the effect of cholesterol was not significant. Each of the three host factors significantly increased several virulence-related phenotypes in V. anguillarum, i.e. protease activity, flagellar motility, biofilm formation and exopolysaccharide production, whereas there was no effect on growth of the bacterium under these conditions. Furthermore, the host factors increased the expression of genes involved in these phenotypes, i.e. the metalloprotease empA, the flagellar transcriptional regulator fleQ, the flagellin gene flaA, the chemotaxis methyltransferase gene cheR, the exopolysaccharide biosynthesis gene wbfD and the exopolysaccharide export gene wza. Our results indicate that V. anguillarum uses host mucin, bile salts, and cholesterol as cues to promote the expression of several important virulence traits that enhance the success of transmission from one host to another. © 2014 Elsevier B.V.

PubMed | Ecloserie Marine de Gravelines, Ghent University, Royal Belgian Institute Of Natural Sciences and Belgium Institute for Agricultural and Fisheries Research
Type: Journal Article | Journal: PloS one | Year: 2014

Impact assessments of offshore wind farm installations and operations on the marine fauna are performed in many countries. Yet, only limited quantitative data on the physiological impact of impulsive sounds on (juvenile) fishes during pile driving of offshore wind farm foundations are available. Our current knowledge on fish injury and mortality due to pile driving is mainly based on laboratory experiments, in which high-intensity pile driving sounds are generated inside acoustic chambers. To validate these lab results, an in situ field experiment was carried out on board of a pile driving vessel. Juvenile European sea bass (Dicentrarchus labrax) of 68 and 115 days post hatching were exposed to pile-driving sounds as close as 45 m from the actual pile driving activity. Fish were exposed to strikes with a sound exposure level between 181 and 188 dB re 1 Pa.s. The number of strikes ranged from 1739 to 3067, resulting in a cumulative sound exposure level between 215 and 222 dB re 1 Pa.s. Control treatments consisted of fish not exposed to pile driving sounds. No differences in immediate mortality were found between exposed and control fish groups. Also no differences were noted in the delayed mortality up to 14 days after exposure between both groups. Our in situ experiments largely confirm the mortality results of the lab experiments found in other studies.

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