Presence of Vibrio mediterranei associated to major mortality in stabled individuals of Pinna nobilis L.

A major epizootic event attributed to Haplosporidium pinnae leading to 100% mortality of Pinna nobilis L. populations along Mediterranean coastlines started in the fall of 2016. As a result, a project to rescue 221 adult individuals of the endangered pen shell, Pinna nobilis was conducted in November 2017 in the two areas of the Spanish coast where the species was still abundant and apparently free from infection by H. pinnae: Port Lligat in the Costa Brava, and the Alfacs Bay in the Ebro Delta. For biosecurity reasons, the 106 individuals from the Ebro Delta were stabled at the IRTA facilities located next to Alfacs Bay, whereas the 115 individuals from Port Lligat were stabled in different institutions throughout the Spanish territory. Initial biopsies showed that individuals from the Ebro Delta were free of the parasite, whereas most individuals from Port Lligat were already parasitized and died in the following months. Individuals at IRTA were hold in five tanks and fed ca. 4% of their dry weight with a mix of three species of phytoplankton and fine riverine sediments (13% OM). Seawater was filtered through 10, 5 and 1 μm to ensure the absence of the parasite and disinfected with UV light. No individuals died during the 4 initial months of captivity, but two died in April–May at temperatures from 17 to 19 °C. A peak of mortalities occurred during the summer months and early fall (53%) with maximums coinciding with temperatures above 25 °C. Individuals were again analyzed by PCR and histology for the presence of H. pinnae, Mycobacteria sp., and other locally important pathogens of commercial bivalves (Vibrio splendidus, V. aestuarianus and Herpesvirus OsHV-1 microVar), and therefore considered as potential pathogens of pen shells. However, with the exception of 3 individuals that were positive for Mycobacteria sp., results were all negative for the studied pathogens. Microbiological culture and isolation of bacteria from three moribund individuals, sacrificed for study purposes, showed V. mediterranei as the dominant species, and further PCR analyses confirmed the presence of the bacterium in ten deceased individuals. Overall, our results suggest the V. mediterranei is an opportunistic pathogen of stabled individuals possibly subjected to stress from captivity, and that antibiotic treatment (Florfenicol) combined with vitamins and mineral supplementation and reduction of water temperature (15 to 18 °C), can be used to mitigate (not to eradicate) the disease. Further research is needed to determine diets and stabling conditions that minimize captivity stress and prevent the emergence of the disease.info:eu-repo/semantics/acceptedVersio

Food determines ephemerous and non-stable gut microbiome communities in juvenile wild and farmed Mediterranean fish

Novel insights were provided by contrasting the composition of wild and farmed fish gut microbiomes because the latter had essentially different environmental conditions from those in the wild. This was reflected in the gut microbiome of the wild Sparus aurata and Xyrichtys novacula studied here, which showed highly diverse microbial community structures, dominated by Proteobacteria, mostly related to an aerobic or microaerophilic metabolism, but with some common shared major species, such as Ralstonia sp. On the other hand, farmed non-fasted S. aurata individuals had a microbial structure that mirrored the microbial composition of their food source, which was most likely anaerobic, since several members of the genus Lactobacillus, probably revived from the feed and enriched in the gut, dominated the communities. The most striking observation was that after a short fasting period (86 h), farmed gilthead seabream almost lost their whole gut microbiome, and the resident community associated with the mucosa had a very much reduced diversity that was highly dominated by a single potentially aerobic species Micrococcus sp., closely related to M. flavus. The results pointed to the fact that, at least for the juvenile S. aurata studied, most of the microbes in the gut were transient and highly dependent on the feed source, and that only after fasting for at least 2 days could the resident microbiome in the intestinal mucosa be determined. Since an important role of this transient microbiome in relation to fish metabolism could not be discarded, the methodological approach needs to be well designed in order not to bias the results. The results have important implications for fish gut studies that could explain the diversity and occasional contradictory results published in relation to the stability of marine fish gut microbiomes, and might provide important information for feed formulation in the aquaculture industry.info:eu-repo/semantics/publishedVersio

Food determines ephemerous and non-stable gut microbiome communities in juvenile wild and farmed Mediterranean fish

Novel insights were provided by contrasting the composition of wild and farmed fish gut microbiomes because the latter had essentially different environmental conditions from those in the wild. This was reflected in the gut microbiome of the wild Sparus aurata and Xyrichtys novacula studied here, which showed highly diverse microbial community structures, dominated by Proteobacteria, mostly related to an aerobic or microaerophilic metabolism, but with some common shared major species, such as Ralstonia sp. On the other hand, farmed non-fasted S. aurata individuals had a microbial structure that mirrored the microbial composition of their food source, which was most likely anaerobic, since several members of the genus Lactobacillus, probably revived from the feed and enriched in the gut, dominated the communities. The most striking observation was that after a short fasting period (86 h), farmed gilthead seabream almost lost their whole gut microbiome, and the resident community associated with the mucosa had a very much reduced diversity that was highly dominated by a single potentially aerobic species Micrococcus sp., closely related to M. flavus. The results pointed to the fact that, at least for the juvenile S. aurata studied, most of the microbes in the gut were transient and highly dependent on the feed source, and that only after fasting for at least 2 days could the resident microbiome in the intestinal mucosa be determined. Since an important role of this transient microbiome in relation to fish metabolism could not be discarded, the methodological approach needs to be well designed in order not to bias the results. The results have important implications for fish gut studies that could explain the diversity and occasional contradictory results published in relation to the stability of marine fish gut microbiomes, and might provide important information for feed formulation in the aquaculture industry.This study was funded by the Spanish Ministry of Science and Innovation projects CTM2017-91490-EXP, PGC2018-096956-B-C41, RTC-2017-6405-1 and PID2021-126114NB-C42, which were also supported by the European Regional Development Fund (FEDER). RRM acknowledges financial support from a sabbatical stay at Helmholz Zentrum München by grant PRX21/00043, which was also from the Spanish Ministry of Science, Innovation and Universities. TV acknowledges the “Margarita Salas” postdoctoral grant, funded by the Spanish Ministry of Universities, within the framework of the Recovery, Transformation and Resilience Plan funded by the European Union (NextGenerationEU), with the participation of the University of the Balearic Islands (UIB). AP was supported by an FPI pre-doctoral fellowship (ref. FPI/2269/2019) from the Balearic Islands Government General Direction of Innovation and Research. AR was supported by a pre-doctoral grant (PRE2019-091259) linked to the ADIPOQUIZ project (RTI2018-095653-R-I00), funded by the Spanish Ministry of Science and Innovation.The research was carried out within the framework of the activities of the Spanish Government through the “Maria de Maeztu Centre of Excellence” accreditation to IMEDEA (CSIC-UIB) (CEX2021-001198).With funding from the Spanish government through the ‘María de Maeztu Unit of Excelence’ accreditation (CEX2021-001198).Peer reviewe

Rapid capture and detection of ostreid herpesvirus-1 from Pacific oyster Crassostrea gigas and seawater using magnetic beads.

Ostreid herpesvirus-1 (OsHV-1) has been involved in mass mortality episodes of Pacific oysters Crassostrea gigas throughout the world, causing important economic losses to the aquaculture industry. In the present study, magnetic beads (MBs) coated with an anionic polymer were used to capture viable OsHV-1 from two types of naturally infected matrix: oyster homogenate and seawater. Adsorption of the virus on the MBs and characterisation of the MB-virus conjugates was demonstrated by real-time quantitative PCR (qPCR). To study the infective capacity of the captured virus, MB-virus conjugates were injected in the adductor muscle of naïve spat oysters, using oyster homogenate and seawater without MBs as positive controls, and bare MBs and sterile water as negative controls. Mortalities were induced after injection with MB-virus conjugates and in positive controls, whereas no mortalities were recorded in negative controls. Subsequent OsHV-1 DNA and RNA analysis of the oysters by qPCR and reverse transcription qPCR (RT-qPCR), respectively, confirmed that the virus was the responsible for the mortality event and the ability of the MBs to capture viable viral particles. The capture of viable OsHV-1 using MBs is a rapid and easy isolation method and a promising tool, combined with qPCR, to be applied to OsHV-1 detection in aquaculture facilities

Vibrio aestuarianus associated to Pacific oyster Crassostrea gigas mortality in the Ebro Delta, in the Catalan Mediterranean Coast

AQUA 2018, #WeRAquaculture we are the producers and investors, the scientists and technical advisors, the legislators and educators, the students, civil society organizations and consumers of farmed aquatic products, 25-29 August 2018, Montpellier, FranceThe presence of Vibrio aestuarianus has been associated to mortality events in pre-commercial and commercial Crassostrea gigas Pacific Oyster in recent years in France and Ireland. However, no mortality events associated to this pathogen has been detected in the Mediterranean. In May 2017, when temperatures were around 20 ºC, C. gigas cultures in the Ebro bays (Alfacs and Fangar) experimented for the first time a massive mortality event of commercial size oyster. Different analyses for detecting the presence of pathogens (qPCR Saulnier et al. 2009 V. aestuarianus/ V. splendidus; qPCR Webb et al. 2007 herpesvirus OsHv-1), as well as presence of contaminants, were performed. Retrospective samples from 2016 were also studied. Results regarding presence of pathogens pointed out the detection of 22+/30 V. aestuarianus positive individuals for oysters with 50% mortality collected in April 2016 (EFCgAbr16), as well as 9+/30 positive individuals in May 2017 adult oyster mass mortality (FmCgMa17). Furthermore, in this last sample the presence of V. splendidus clade was also observed, however similar results were also observed in oyster with no mortality. The V. aestuarinus presence was corroborated by the Spanish National Reference Laboratory (CSIC-Vigo) on samples with mortalities collected from the same bay one month later. Results on contaminant analysis revealed the presence of metolachlor (organitrogen pesticide), bentazone (insecticide), methylparaben (endocrine disruptors), with levels ranging from less than 1 ng/g dry weight (dw) to 10 ng/g dw for both oysters experiencing mortality and with no mortality. Furthermore, esterase activities indicative of OP pesticide exposure did not suggest neurotoxicity signs caused by these compounds. Those results do not support association of contaminants with the studied mortality events and the cause seems of pathogenic aetiology. Present results indicate the first detection of Vibrio aestuarianus associated to commercial Crassostrea gigas mortality in the Ebro Delta shellfish culture site, at the Catalan Mediterranean coast, as well as for Mediterranean oyster culture in general. First sample detected positive dates from April 2016 and had been immersed in the Ebro Delta two weeks earlier, coming from French Atlantic waters. Those samples are now being further studied by histology to discard other potential pathogens involved to the mortality episodes. In the case of commercial adult oyster mortality in May 2017 (FmCgMa17), the potential influence of a pathogenic V. splendidus strain being also involved cannot be discardedThe research leading to these results has received funding from the European Union's H2020 Framework Programme under grant agreement no 678589 (VIVALDI project) and from the Spanish Government with the INIA E-RTA2015-00004-00-00 project (EMERGER). As well with the project XENOMETABOLOMIC (CTM2015-73179-JIN) (AEI/FEDER/UE) and AimCost project (CGL2016-76332-R MINECO/FEDER, UE)Peer Reviewe

Presence of Vibrio mediterranei associated to major mortality in stabled individuals of Pinna nobilis L

A major epizootic event attributed to Haplosporidium pinnae leading to 100% mortality of Pinna nobilis L. populations along Mediterranean coastlines started in the fall of 2016. As a result, a project to rescue 221 adult individuals of the endangered pen shell, Pinna nobilis was conducted in November 2017 in the two areas of the Spanish coast where the species was still abundant and apparently free from infection by H. pinnae: Port Lligat in the Costa Brava, and the Alfacs Bay in the Ebro Delta. For biosecurity reasons, the 106 individuals from the Ebro Delta were stabled at the IRTA facilities located next to Alfacs Bay, whereas the 115 individuals from Port Lligat were stabled in different institutions throughout the Spanish territory. Initial biopsies showed that individuals from the Ebro Delta were free of the parasite, whereas most individuals from Port Lligat were already parasitized and died in the following months. Individuals at IRTA were hold in five tanks and fed ca. 4% of their dry weight with a mix of three species of phytoplankton and fine riverine sediments (13% OM). Seawater was filtered through 10, 5 and 1 μm to ensure the absence of the parasite and disinfected with UV light. No individuals died during the 4 initial months of captivity, but two died in April–May at temperatures from 17 to 19 °C. A peak of mortalities occurred during the summer months and early fall (53%) with maximums coinciding with temperatures above 25 °C. Individuals were again analyzed by PCR and histology for the presence of H. pinnae, Mycobacteria sp., and other locally important pathogens of commercial bivalves (Vibrio splendidus, V. aestuarianus and Herpesvirus OsHV-1 microVar), and therefore considered as potential pathogens of pen shells. However, with the exception of 3 individuals that were positive for Mycobacteria sp., results were all negative for the studied pathogens. Microbiological culture and isolation of bacteria from three moribund individuals, sacrificed for study purposes, showed V. mediterranei as the dominant species, and further PCR analyses confirmed the presence of the bacterium in ten deceased individuals. Overall, our results suggest the V. mediterranei is an opportunistic pathogen of stabled individuals possibly subjected to stress from captivity, and that antibiotic treatment (Florfenicol) combined with vitamins and mineral supplementation and reduction of water temperature (15 to 18 °C), can be used to mitigate (not to eradicate) the disease. Further research is needed to determine diets and stabling conditions that minimize captivity stress and prevent the emergence of the disease.info:eu-repo/semantics/acceptedVersio