Pacific Cupped Oyster Crassostrea Gigas Research Articles

First characterization of the parasite Haplosporidium costale in France and development of a real-time PCR assay for its rapid detection in the Pacific oyster, Crassostrea gigas.

The Pacific cupped oyster Crassostrea gigas is one of the most 'globalized' marine invertebrates and its production is predominant in many parts of the world including Europe. However, it is threatened by mortality events associated with pathogenic microorganisms such as the virus OsHV-1 and the bacteria Vibrio aestuarianus. C. gigas is also a host for protozoan parasites including haplosporidians. In contrast with Haplosporidium nelsoni previously detected in Europe, H. costale was considered exotic although its presence in French oysters was suggested in the 1980s based on ultrastructural examination. Here, a combination of light and transmission electron microscopy, PCR and sequencing allowed characterizing the presence of the parasite in the context of low mortality events which occurred in 2019 in France. Histological observation revealed the presence of uninucleated, plasmodial and spore stages within the connective tissues of some oysters. Ultrastructural features were similar to H. costale ones in particular the presence of axe-shaped haplosporosomes in spore cytoplasms. Three fragments of the genome including partial small subunit rRNA gene, the ITS-1, 5.8S and ITS-2 array and part of the actin gene were successfully sequenced and grouped with H. costale homologous sequences. This is the first time that the presence of H. costale was confirmed in C. gigas in France. Furthermore, a TaqMan real-time PCR assay was developed and validated [DSe=92.6% (78.2-99.8) and DSp=95.5% (92.3-98.6)] to enable the rapid and specific detection of the parasite. The application of the PCR assay on archived samples revealed that the parasite has been present in French oyster populations at least since 2008. Considering the little information available on this parasite, the newly developed TaqMan assay will be very helpful to investigate the temporal and geographic distribution and the life cycle of the parasite in France and more generally in C. gigas geographic range.

Effect of temperature on the toxicokinetics and gene expression of the pacific cupped oyster Crassostrea gigas exposed to cadmium

In this study, we investigated the influence of temperature on the bioaccumulation and depuration of Crassostrea gigas exposed to Cd associated with its molecular responses. Oysters were acclimatized to different temperatures (10 °C, 15 °C, 20 °C, 25 °C, and 30 °C) for 14 d and then exposed to 10 μg/L Cd for 28 d, followed by a depuration period of 35 d. Oysters were sampled for chemical analysis by inductively coupled plasma mass spectrometry (ICP-MS) and for mRNA quantification by qPCR. In the digestive gland, gill, and mantle, the cadmium concentration at 10 °C was significantly lower than that at 25 °C and 30 °C in both the whole experiments. The use of a two-compartment model showed that the uptake rate k1 in the above three tissues increased with increasing temperatures ranging from 15 to 25 °C. The fastest elimination rates and shortest half-lives were observed at 15–25 °C. The induction of metallothionein (MT) only occurred in the digestive gland at 15 °C and 20 °C at the end of the accumulation phase. In the mantle and gills, the expression of P-glycoprotein (P-gp) was significantly induced at the end of the accumulation phase and significantly inhibited at the end of the depuration phase. In the digestive gland, the expression of P-gp was induced at the end of both the accumulation and depuration phases. Heat shock protein (hsp70) expression exhibited an overall increasing trend throughout the experiment.

Diet variably affects the trophic transfer of trace elements in the oyster Crassostrea gigas

Although it has been shown that trophic transfer of trace elements in oysters can be influenced by the diet, most of the studies investigating the ability of oysters to bioaccumulate trace elements from their diet are based on experiments using phytoplankton alone. Wild oysters feed also on large bacteria, ciliates or detritic organic matter. The present study aimed at examining the influence of food quality on the assimilation efficiency (AE) of trace elements in the Pacific cupped oyster Crassostrea gigas. Oysters were exposed via their food to the radiotracers of essential (57Co, 54Mn and 65Zn) and non-essential (110mAg, 241Am and 109Cd) trace elements under different diets (protozoan ciliates Uronema marinum and diatoms Thalassiosira pseudonana). Significant differences were found only for Ag and 241Am, with lower AEs measured in oysters fed with ciliates than in individuals fed with diatoms (Ag: 54 ± 3% vs. 67 ± 4% and 241Am: 62 ± 4% vs. 76 ± 4%). Interestingly, no significant difference was found among estimated depuration rates (kel) for all trace elements ingested with the two diets tested. These findings indicate that the differences observed are driven by the digestion process, presumably due to difference of bioavailability of trace elements dependent on the quality of the food ingested.

Influence of food (ciliate and phytoplankton) on the trophic transfer of inorganic and methyl-mercury in the Pacific cupped oyster Crassostrea gigas

Diet is an important route of mercury (Hg) uptake in marine organisms. Trophic transfer of Hg throughout the food webs may be influenced by various factors, including diet and Hg speciation. Bivalves such as oysters are widely used as bioindicators of trace element pollution such as Hg. Nevertheless, our current knowledge regarding their ability to accumulate Hg from their diet is mainly based on experiments performed using phytoplankton. In their natural environment, oysters feed on a variety of food items including ciliates, detritus, in addition to phytoplankton. The present study aimed at examining the influence of diet composition on the trophic transfer of inorganic Hg (iHg) and methylmercury (MeHg) in the Pacific cupped oyster Crassostrea gigas. The pulse-chase feeding method was used with two radiolabeled food items: a heterotrophic protist (Uronema marinum) and a phytoplanktonic diatom (Thalassiosira pseudonana). Depuration of dietary Hg in the oysters was followed for 50 d. Kinetic parameters including assimilation efficiency (AE) and efflux rate constant (ke) were calculated. Our results showed that oysters fed on ciliates assimilated 96 ± 1% and 31 ± 2% of the ingested MeHg and iHg, respectively whereas these elements were similarly assimilated in the oysters fed on phytoplankton (78 ± 3% and 86 ± 4% for MeHg and iHg, respectively). Mercury assimilation in oyster is thus diet dependent (significant differences in AE, p < 0.05), metal species-dependent and likely resulting from variations in Hg bioavailability in the two food items tested and a gut passage time-dependent of the ingested matrix.

Development of a duplex Taqman real-time PCR assay for rapid identification of Vibrio splendidus-related and V. aestuarianus strains from bacterial cultures

To enable the rapid and accurate identification of Vibrio splendidus-related and V. aestuarianus strains associated with Pacific cupped oyster Crassostrea gigas mortality, we developed a duplex Taqman real-time PCR assay and evaluated its efficacy. This technique proved to be rapid, sensitive, and specific and will be particularly valuable for epidemiologic studies.

Mollusc disease situation in Europe : what’s new since 2008 ?

Event Abstract Back to Event Mollusc disease situation in Europe : what’s new since 2008 ? Isabelle Arzul1*, Axel Osta Amigo1 and Coralie Lupo1 1 Ifremer, SG2M-LGPMM, France In Europe, surveillance effort regarding mollusc diseases is different between Member States and partly depends on the amount and the diversity of the shellfish production. Some countries implement active surveillance of pathogens regulated at the European level including Bonamia ostreae and Marteilia refringens. Non-regulated pathogens such as OsHV-1-µvar or Perkinsus olseni are also the target of some national active surveillance programmes. In addition, many European countries carry out passive surveillance based on abnormal mortality reports. However, mortality reporting relies on the good will of producers/fishermen (Lupo et al. 2012) and differs between mollusc species. Indeed, abnormal mortality reports in Europe mostly concern the Pacific cupped oyster Crassostrea gigas, and, in a lesser concern, mussels and clams. Very occasionally mortality is reported on other less accessible species including scallops Pecten maximus or flat oyster Ostrea edulis. The advantages and limits of these surveillance systems are discussed through examples of mollusc pathogen emergence in Europe since 2008. These data have been collected through the network of National Reference Laboratories (NRLs) of mollusc diseases. Since these last years, implemented surveillance programmes have allowed better defining the geographic distribution of some mollusc pathogens. For example, the protozoan parasite M. refringens has been detected in locations for which partial data was previously available such as in the Adriatic Sea. The protozoan parasite B. exitiosa, previously considered exotic to Europe has been detected in different European countries sometimes in the context of mortality events but more often in the context of active surveillance programme (Arzul et al. 2011). In few Member States, surveillance programmes have been carried out to achieve and maintain free status regarding some pathogens in some zones or for the whole country. This surveillance effort has sometimes contributed to detect pathogens like OsHV-1µvar and B. ostreae in previously free locations. Finally, these different active and passive surveillance programmes have contributed to characterize new pathogens. For example, the protozoan parasite Marteilia cochillia has been detected in association with mortality of cockles in Spain (Carrasco et al. 2011) and in the context of wild population monitoring (Villalba et al. 2014). Parasites of the genus Mikrocytos have been observed in the context of mortality events affecting different mollusc species including Donax trunculus in France (Garcia et al. 2012), Ruditapes philippinarum in Spain and The Netherlands or Crassostrea gigas in United Kingdom (Hartikainen et al. 2014). Transfer of animals and depuration centers seem to contribute to the spread of mollusc pathogens. However, the source of these apparently new pathogens is often difficult to identify. These examples question the means to prevent and mitigate mollusc diseases in a production which generally takes place in open areas and in the context of which treatment and vaccination is not conceivable. Acknowledgements We would like to thank the network of NRLs for Mollusc Diseases. References Arzul, I., Aranguren, R., Arcangeli, G., Cheslett, D., Couraleau, Y., Engelsma, M., Figueras, A., Garcia, C., Geoghegan, F., Magnabosco, C., Stone, D. (2011). Distribution and Variability of Bonamia exitiosa in flat oyster Ostrea edulis populations in Europe. Journal of Shellfish Research 31(1), 300 Carrasco, N., Roque, A., Andree, K.B., Rodgers, C., Lacuesta, B., Furones, M.D. (2011). A Marteilia parasite and digestive epithelial virosis lesions observed during a common edible cockle Cerastoderma edule mortality event in the Spanish Mediterranean coast. Aquaculture 321, 197-202. Garcia, C., Arzul, I., Joly, J.P., Guichard, B., Chollet, B., Omnes, E., Haond, C., Robert, M., Lupo, C., Francois, C. (2012). Mikrocytos like protozoans and the shellfish Donax trunculus mortality events in France. Journal of Shellfish Research 31, 273). Hartikainen, H., Stentiford, G.D., Bateman, K.S., Berney, C., Feist, S.W., Longshaw, M., Okamura, B., Stone, D., Ward, G., Wood C., Bass D. (2014). Mikrocytids are a broadly distributed and divergent radiation of parasites in aquatic invertebrates. Current Biology 24, 807-812 Lupo, C., Osta Amigo, A., Mandard, Y.V., Peroz C., Renault, T. (2012). Improving early detection of exotic or emergent oyster diseases in France: Identifying factors associated with shellfish farmer reporting behaviour of oyster mortality, Preventive Veterinary Medicine 116, 168-182. Villalba, A., Iglesias, D., Ramilo, A., Darriba, S., Parada, J., No, E., Abollo, E., Molares, J., Carballal, M.J. (2014). Cockle Cerastoderma edule fishery collapse in the Ría de Arousa (Galicia, NW Spain) associated with the protistan parasite Marteilia cochillia . Dis Aquat Org 109, 55-80 Keywords: Mollusc diseases, disease surveillance, Mollusc disease surveillance, Pathogen emergence, Network of National Rference Laboratories Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016. Presentation Type: Oral Topic: Aquatic Animal Epidemiology Citation: Arzul I, Osta Amigo A and Lupo C (2016). Mollusc disease situation in Europe : what’s new since 2008 ?. Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00054 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 May 2016; Published Online: 14 Sep 2016. * Correspondence: Dr. Isabelle Arzul, Ifremer, SG2M-LGPMM, La Tremblade, France, Isabelle.Arzul@ifremer.fr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Isabelle Arzul Axel Osta Amigo Coralie Lupo Google Isabelle Arzul Axel Osta Amigo Coralie Lupo Google Scholar Isabelle Arzul Axel Osta Amigo Coralie Lupo PubMed Isabelle Arzul Axel Osta Amigo Coralie Lupo Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Novel quantitative TaqMan® MGB real-time PCR for sensitive detection of Vibrio aestuarianus in Crassostrea gigas.

Validation of a novel quantitative real-time PCR using TaqMan® minor groove binder (MGB) chemistry is described for sensitive and rapid detection of Vibrio aestuarianus, an increasingly important pathogen of Pacific cupped oyster Crassostrea gigas aquaculture. Primers and TaqMan® MGB hydrolysis probe were designed to specifically amplify a 58bp DNA fragment of the V. aestuarianus dnaJ gene. Real-time PCR selectivity was empirically tested using DNA extracted from isolates of V. aestuarianus and a selection of different aquatic bacterial species, including other Vibrio spp. Theoretical selectivity was assessed through sequence comparison using the NCBI BLAST similarity tool. Quantitative PCR plasmid standards were generated to test assay linearity, amplification efficiency and the limit of quantitation (LOQ), according to International Organisation for Standardisation ISO 16140 validation recommendations. LOQ ranged between 5 and 10 PCR copies, although the detection range extended beyond this with reduced precision. Applied performance was tested using C. gigas samples taken from a selection of Irish aquaculture sites. Increasing levels of V. aestuarianus, accompanied by the development of tissue pathology in examined oysters, were found at 1 site that was sampled repeatedly in 2013. Rapid, sensitive and reproducible detections of V. aestuarianus from C. gigas tissue samples were attained during this validation study with a small sample size, and a practical application for disease management is described.

Detection of Type 1 Ostreid Herpes variant (OsHV-1 μvar) with no associated mortality in French-origin Pacific cupped oyster Crassostrea gigas farmed in Italy

In April 2010, the sampling of juvenile Pacific cupped oysters originating from France was undertaken from a farm located off the coast of the Marche region in Italy. Samples were sent to the national reference laboratory for mollusc diseases for bacteriological, histological, electron microscopical and molecular analysis. Classical and Real-Time PCR indicated the presence of the microvariant (OsHV-1 μvar) of Type 1 Ostreid Herpes virus (OsHV-1) despite the absence of clinical and pathological signs normally associated with the presence of this variant. Further molecular and sequencing analysis revealed the presence of OsHV-1 μvar and OsHV-1 DNA in one oyster indicating that simultaneous detection of both viruses is possible. This is the first report of the presence of OsHV-1 μvar in Italy and also the first time that evidence of possible co-infection of OsHV-1 and OsHV-1 μvar has been provided.

The top 27 animal alien species introduced into Europe for aquaculture and related activities

Summary The information extracted from IMPASSE, DAISIE, FishBase, and FAO-DIAS inventories of alien species were used to draw a list of the 27 most utilized animal alien species for aquaculture and related activities (e.g. stocking, sport fishing, ornamental purposes) in Europe. Three variables have been considered to assess their negative ecological impacts when these species escape from aquaculture facilities: (i) their distribution across Europe (including non-EU Member States); (ii) evidence of their environmental impact in the wild; and (iii) evidence of their being vectors of non-target alien species and other hitchhikers (e.g. pathogens). Drivers of use and mechanisms of dispersal in the wild have been also considered and reviewed. Twenty of the species are freshwater fishes: alien cyprinids and salmonids have been introduced into Europe mainly for food production, sport fishing and ornamental purposes. The most widespread species are the goldfish Carassius auratus and the rainbow trout Oncorhynchus mykiss, established in 29 and 28 European countries, respectively. Notwithstanding their successful distribution in Europe, only the Gibel carp Carassius gibelio and the peneid shrimp Marsupenaeus japonicus were found to have environmental impact in all the countries of establishment. Crayfish and predatory fishes (e.g. catfishes and salmonids) cause major environmental impacts in Europe by outcompeting native species and altering habitat structure. Alien crayfish, Procambarus clarkii and Pacifastacus leniusculus, are responsible for the largest range of impacts (i.e. crayfish plague dissemination, bioaccumulation of pollutants, community dominance, competition and predation on native species, habitat modifications, food web impairment, herbivory and macrophytes removal). Cyprinids (e.g. herbivorous carps) are vectors of diseases and parasites, while salmonids (e.g. Salvelinus fontinalis) often cause genetic impairment of native stocks by hybridization. The importation of alien farmed (target) species frequently leads to the introduction of associated non-target species. The cultures of the Pacific cupped oyster Crassostrea gigas and Manila clam Ruditapes philippinarum were responsible for the introduction of the largest number (60) of non-native invertebrates and algae, often attached to packaging material, fouling the shell or parasitizing bivalve tissues.

Experimental ostreid herpesvirus 1 infection of the Pacific oyster Crassostrea gigas: Kinetics of virus DNA detection by q-PCR in seawater and in oyster samples

Herpes- and herpes-like viruses are known to infect a wide range of bivalve mollusc species throughout the world. Abnormal summer mortalities associated to the detection of ostreid herpesvirus 1 (OsHV-1) have been currently reported in France among larvae and spat of the Pacific cupped oyster Crassostrea gigas. In the present work, we have developed an experimental protocol of horizontal transmission based on the cohabitation between healthy and experimentally infected oysters. Through a cohabitation trial, the kinetics of OsHV-1 detection in different oyster organs and seawater samples were investigated and characterized for the first time using real time quantitative PCR.

Comparative physiological energetics of two suspension feeders: polychaete annelid Lanice conchilega (Pallas 1766) and Pacific cupped oyster Crassostrea gigas (Thunberg 1795)

Feeding competition between the Pacific cupped oyster Crassostrea gigas and the polychaete Lanice conchilega was studied by assessing the polychaete suspension feeding activity. Retention efficiency was estimated by comparing particle size distributions at the output of experimental chambers containing the species and controls. Although particles ranging from 4 to 12 μm were collected by L. conchilega, no upper threshold or maximum retention rate was reached within this range. In contrast, C. gigas showed retention starting at 2 μm, and reaching an upper threshold at 6 to 8 μm. Based on our results, feeding competition is likely to occur between C. gigas and L. conchilega. Standardised filtration rates reached 0.225 l h −1 g dmw −1 (±0.08) for L. conchilega and 2.43 l h −1 g dmw −1 C. gigas for animals of 1 g dry meat weight (dmw). Assimilation rates, 0.44 for L. conchilega and 0.49 for C. gigas, were similar for the two species. Respiration rates were estimated at 0.113 and 0.68 ml O 2 h −1 for L. conchilega (Allometric coefficient=0.534) and C. gigas respectively. Therefore polychaete scope for growth (SFG) (4.01 J h −1 g dmw −1) was significantly lower when compared with C. gigas SFG (61.96 J h −1 g dmw −1). The impact of the L. conchilega population on that of cultivated oysters was evaluated from these results and field population assessment of both species. Based on field population estimates, L. conchilega was responsible for a 19% decrease in the carrying capacity and 30% of the oxygen depletion from the total activity of both species. However, L. conchilega SFG was only 16% of that of the C. gigas population. Several hypotheses regarding population interactions are discussed.