Ostrea Edulis Research Articles

Cryopreservation of European flat oyster (Ostrea edulis) larvae using a controlled-rate freezer

Larvae of the European flat oyster (Ostrea edulis) were cryopreserved using two protocols originally developed for other bivalvian species with several modifications. Culture of the European flat oyster went through several setbacks due to parasitic diseases, thus, assisted reproductive technologies such as larval cryopreservation can aid in prompt restoration of lost populations and thus facilitate farming of the species. Veliger larvae were diluted in two basic extenders (0.4 M trehalose or 0.4 M sucrose) supplemented with ethylene glycol (EG), dimethyl-sulfoxide (DMSO) or propylene glycol (PG) in concentrations of 10–20% with or without the addition of polyvinylpyrrolidone (average MW-40,000; PVP-40). Larvae were loaded into 0.25-ml or 0.5-ml straws and cryopreserved in a controlled-rate freezer using two slow cooling profiles. Assessment of larval survival 20 min or 24 h post-thaw revealed that the cooling profiles and the type of extender used did not have a significant effect on survival rates. On the other hand, the type of cryoprotectant, straw volume and the time of assessment had a significant main effect on larval survival percentages (p < 0.001 in all three cases). Survival percentages of 70–80% were observed 20 min post-thaw which decreased to 40–60% at 24 h. Generally, EG and DMSO resulted in higher post-thaw larval survival than did PG when larvae were cryopreserved in 0.25-ml straws, whereas, these differences were not detected when 0.5-ml straws were employed. Results of these experiments will allow later studies on long-term survival of cryopreserved European flat oyster larvae.

Integrated multi-trophic aquaculture of the European flat oyster (Ostrea edulis Linnaeus, 1758): A case study from Boka Kotorska Bay (Montenegro)

Integrated multi-trophic aquaculture of the European flat oyster (Ostrea edulis Linnaeus, 1758): A case study from Boka Kotorska Bay (Montenegro)

Loop-Mediated Isothermal Amplification for the Fast Detection of Bonamia ostreae and Bonamia exitiosa in Flat Oysters.

The haplosporidian parasites Bonamia ostreae (BO) and B. exitiosa (BE) are serious oyster pathogens. Two independent laboratories evaluated fluorescence real-time loop-mediated isothermal amplification (LAMP) assays for rapidly detecting these parasites. Specific LAMP assays were designed on the BO actin-1 and BE actin genes. A further generic assay was conceived on a conserved region of the 18S gene to detect both Bonamia species. The optimal reaction temperature varied from 65 to 67 °C depending on the test and instrument. Melting temperatures were 89.8-90.2 °C, 87.0-87.6 °C, and 86.2-86.6 °C for each of the BO, BE, and generic assays. The analytical sensitivity of these assays was 50 copies/µL in a 30 min run. The BO and BE test sensitivity was ~1 log lower than a real-time PCR, while the generic test sensitivity was similar to the real-time PCR. Both the BO and BE assays were shown to be specific; however, the generic assay potentially cross-reacts with Haplosporidium costale. The performance of the LAMP assays evaluated on samples of known status detected positives within 7-20 min with a test accuracy of 100% for the BO and generic tests and a 95.8% accuracy for BE. The ease of use, rapidity and affordability of these tests allow for field deployment.

Increased seawater temperature triggers thermal, oxidative and metabolic response of Ostrea edulis, leading to anaerobiosis

Bivalves are among the marine organisms most influenced by climate change. Despite the flat oyster's Ostrea edulis high economic value, its culture is developed on a very small scale, since this species possesses a strong susceptibility to abiotic stressors. Due to climate change, temperature is one of the most critical environmental parameters for the welfare of the Mediterranean basin's marine inhabitants. The present study's purpose was to investigate the physiological performance of the Mediterranean's native O. edulis as it faces exposure to different temperatures. Since juveniles are more susceptible to abiotic stressors, this experimental procedure was focused on young individuals. The seawater temperatures studied included a standard control temperature of 21 °C (often observed in several marine areas throughout the Mediterranean), as well as increased seawater temperatures of 25 °C and 28 °C, occasionally occurring in shallow Mediterranean waters inhabited by bivalve spat. These were selected since the tissues of O. edulis becomes partly anaerobic in temperatures exceeding 26 °C, while cardiac dysfunction (arrhythmia) emerges at 28 °C. The results demonstrate that temperatures above 25 °C trigger both the transcriptional upregulation of hsp70 and hsp90, and the antioxidant genes Cu/Zn sod and catalase. Enhancement of thermal tolerance and increased defense against increased ROS production during thermal stress, were observed. As the intensity and duration of thermal stress increases, apoptotic damage may also occur. The increased oxidative and thermal stress incurred at the highest temperature of 28 °C, seemed to trigger the switch from aerobic to anaerobic metabolism, reflected by higher pepck mRNA expressions and lower ETS activity.

Evaluation of Mud Worm (Polydora spp.) Infestation in Cupped (Crassostrea gigas) and Flat Oyster (Ostrea edulis) Broodstocks: Comparison between Magnetic Resonance Imaging and Computed Tomography.

The Polichete worms of the genus Polydora are considered very destructive for oysters, excavating channels in their shell and inducing oysters to create mud blisters in response to the irritation, interfering with their physiology and ethology. The parasite also causes important economic damage for oyster farmers, as products with a high degree of infestation cannot be commercialized. The present study aims to evaluate whether two non-invasive advanced diagnostic techniques, computed tomography scans (CT) and magnetic resonance imaging (MRI), are suitable to show the alterations induced by this parasite on live Crassostrea gigas and Ostrea edulis oyster broodstocks. A CT scan is also able to identify small lesions in the shell during the first stage of infection. MRI allows for the visualization of the advanced status of the lesions when blisters occupy the inner surface of the shell and can impact the health status and the economic value of the mollusk. Both techniques resulted in satisfactory spatial resolution, and no motion artifacts were reported, thus enabling the authors to faithfully visualize in vivo the damage caused by the parasite.

Flexible Sensing Enabled Nondestructive Detection on Viability/Quality of Live Edible Oyster.

Environmental and physiological fluctuations in the live oyster cold chain can result in reduced survival and quality. In this study, a flexible wireless sensor network (F-WSN) monitoring system combined with knowledge engineering was designed and developed to monitor environmental information and physiological fluctuations in the live oyster cold chain. Based on the Hazard Analysis and Critical Control Point (HACCP) plan to identify the critical control points (CCPs) in the live oyster cold chain, the F-WSN was utilized to conduct tracking and collection experiments in real scenarios from Yantai, Shandong Province, to Beijing. The knowledge model for shelf-life and quality prediction based on environmental information and physiological fluctuations was established, and the prediction accuracies of TVB-N, TVC, and pH were 96%, 85%, and 97%, respectively, and the prediction accuracy of viability was 96%. Relevant managers, workers, and experts were invited to participate in the efficiency and applicability assessment of the established system. The results indicated that combining F-WSN monitoring with knowledge-based HACCP modeling is an effective approach to improving the transparency of cold chain management, reducing quality and safety risks in the oyster industry, and promoting the sharing and reuse of HACCP knowledge in the oyster cold chain.

Marine bivalves voucher DNA barcoding from Eastern Mediterranean, with evidence for Ostrea stentina invasion

Abstract Bivalve molluscs are a diverse group of animals with particular economic and ecological importance. Their morphological characteristics frequently confuse their identification leading to mislabelling of edible species. Genetic diversity is critical to the resilience of marine bivalve populations in the face of environmental stressors such as ocean acidification and warming. In this study, we characterized the phylogeny and defined the first DNA barcodes of six marine bivalves [Ostrea edulis (Linnaeus, 1758) Arca noae (Linnaeus, 1758), Pinctada radiata (Leach, 1814), Venus verrucosa (Linnaeus, 1758), Calllista chione (Linnaeus, 1758) and Ruditapes decussatus (Linnaeus, 1758)] sampled from different coastal areas of Aegean and Ionian Seas using the molecular markers cytochrome c oxidase subunit I (COI) and 18S ribosomal RNA (18S rRNA). Further, COI gene was employed to investigate the population genetic diversity since 18S rRNA exhibited no conspecific differences. The sequence of 18S rRNA successfully discriminated the bivalves at family or superfamily level but occasionally proved insufficient for species identification. Contrariwise, COI was highly informative and could reliably distinguish all species. Population haplotype diversity was moderate to high and was always accompanied by generally low nucleotide diversity, indicating genetically closely related haplotypes. The invasive Pinctada radiata was found to be panmictic even among distant sampling areas, while Ostrea edulis was the only species that exhibited moderate levels of population subdivision. Finally, here we report for the first time the presence of Ostrea stentina in Thermaikos Gulf sampled among Ostrea edulis specimens, demonstrating a new invasive bivalve species in Eastern Mediterranean.

Marteilia pararefringens infections are more frequent than revealed by the Norwegian surveillance programme, highlighting the need for its improvement.

Norway had historically been considered free of marteiliosis in bivalves since the disease surveillance programme began in 1995. However, in 2016, Marteilia pararefringens, a protistan parasite of mussels Mytilus spp., was described in a heliothermic lagoon-a poll-previously used to produce flat oyster spat. To study whether the parasite was introduced, and possibly spread, via the historical flat oyster networks on the south and west coast, we sampled aquaculture polls that were part of different networks of farmers and wild, natural polls with no aquaculture activity. Additionally, we sampled mussel banks influenced by polls and sheltered bays that could have a similar environment to that of polls. We identified 7 sites with M. pararefringens-infected mussel populations: 5 were polls used in flat oyster production and 2 were in fjord areas with no known connection to any bivalve aquaculture. Prevalence ranged between 2 and 88%. At one site, Trysfjorden, we found M. pararefringens in atypical organs, including the gills, mantle, and intestine. Marteilia-like cells were also observed in the epithelium, lumen, and surrounding connective tissue of metanephridia and in the sinus of the anterior retractor muscle. Our results demonstrate that the parasite is more widespread than previously thought and is neither isolated to polls nor connected directly to aquaculture activity. Lastly, our findings highlight the need for an improved sampling strategy in surveillance programmes to detect marteiliosis in mussels.

The history of the European native oyster Ostrea edulis in Northern Irish waters and the four phases of resource exploitation

An in-depth history of the European native oyster in Northern Irish waters has been absent from international and regional peer-reviewed publications. The knowledge of historical losses and a need to recover ecosystems for habitat and biodiversity purposes are primary drivers in an urgency to restore Ostrea edulis. However, a comprehensive record of O. edulis in Northern Ireland is required to assist with this work. The authors compiled a list of relevant references from grey material, rare historical archives, library collections, government reports and peer-reviewed publications. Archival reviews have been tabulated into a timeline, which documents site location, exploitation, sites of significant interest and socio-economic histories of the coastal communities who relied on the oyster. The reference material identified four distinctive phases of exploitation whereby harvesting transits from personal use to commercialization, collapse and then restoration. The study revealed that O. edulis harvests in the early 1800s in Northern Ireland were predominantly destined for export to supply collapsing stocks throughout Britain. Fishing was intense with the fishery closed by 1903. However, the species has proved to be extremely resilient with small artisanal fisheries still in existence today. This research will offer habitat managers guidance in relation to site selection and anthropogenic pressures when restoring the European flat oyster to the iconic historical beds of the Northern Irish Sea loughs.

Ecotoxicology of Trace Elements in European Oyster (Ostrea edulis), Seawater, and Sedimentsacross Boston Harbor, Massachusetts,USA.

European oyster (Ostrea edulis) can be used for biological monitoring of water and sediment quality and serve as a conduit of trace elements to humans via consumption. Trace element concentrations in seawater, sediment, O. edulis edible tissues and shells from Boston Harbor were studied and found to be elevated relative to comparative studies in native ecosystems in the Adriatic Sea and Bay of Biscay. Average edible oyster tissues concentrations (mg/kg) were: arsenic 6, cadmium 1.7, cobalt 3.1, chromium 1.9, copper 153, mercury 0.265, nickel 1.8, lead 3.3, and zinc 2390. Arsenic was elevated in seawater and oyster shells. Mercury was elevated in sediments and oyster tissues. Lead was elevated in suspended sediments. Total Hazard Quotient (THQ) was < 1 but when summed across trace elements, THQ was nominally > 1 for all sites. Further study is warranted to determine mechanisms and spatial extent of bioaccumulation.

Strategies to improve the postharvest management of flat oyster (Ostrea edulis) from aquaculture using the short-term storage and package in an innovative closed-circuit system.

This study aimed to improve postharvest management of flat oysters reared in a longline system in the mid Adriatic Sea, using short-term storage and package in an innovative closed-circuit system. For the trial, 870 oysters were employed, divided into three experimental groups (A, B, and C), N=270 oysters each group, whereas the remaining 60 oysters were used for the 2 controls. Each group differed in relation to the time spent in the depuration tank and the time of packaging: group A was packed and immediately transferred to the cell; group B was depurated in a tank for 48h, then packed and transferred to the cell; group C was depurated in a tank for 48h and then packed, depurated for another 24h and transferred to a cell. Samples of each group were sampled at different times of permanence in cell (t0) up until 12 days (t12) for biomorphometric, sensorial, nutritional, and microbiological analysis. Although the nutritional and sensorial quality of the oysters was more pronounced in group A, B and C groups also showed good results. In these two groups, thanks to the use of the modern water recirculation system the quality and safety of oysters was improved by reducing the presence of sludge and eliminating fecal contaminants completely than A treatment and seawater control. These results were also confirmed by the tank control, where a more extended depuration period positively influenced the same parameters emphasizing the importance of the adequate depuration processes in oyster production.

Deep Learning-Based Oyster Packaging System

With the deepening understanding of the nutritional value of oysters by consumers, oysters as high-quality seafood are gradually entering the market. Raw edible oyster production lines mainly rely on manual sorting and packaging, which hinders the improvement of oyster packaging efficiency and quality, and it is easy to cause secondary oyster pollution and cross-contamination, which results in the waste of oysters. To enhance the production efficiency, technical level, and hygiene safety of the raw aquatic products production line, this study proposes and constructs a deep learning-based oyster packaging system. The system achieves intelligence and automation of the oyster packaging production line by integrating the deep learning algorithm, machine vision technology, and mechanical arm control technology. The oyster visual perception model is established by deep learning object detection techniques to realize fast and real-time detection of oysters. Using a simple online real-time tracking (SORT) algorithm, the grasping position of the oyster can be predicted, which enables dynamic grasping. Utilizing mechanical arm control technology, an automatic oyster packaging production line was designed and constructed to realize the automated grasping and packaging of raw edible oysters, which improves the efficiency and quality of oyster packaging. System tests showed that the absolute error in oyster pose estimation was less than 7 mm, which allowed the mechanical claw to consistently grasp and transport oysters. The static grasping and packing of a single oyster took about 7.8 s, and the success rate of grasping was 94.44%. The success rate of grasping under different transportation speeds was above 68%.

The genome sequence of the European flat oyster, Ostrea edulis (Linnaeus, 1758).

We present a genome assembly from an individual Ostrea edulis (the European flat oyster; Mollusca; Bivalvia; Ostreida; Ostreidae). The genome sequence is 894.8 megabases in span. Most of the assembly is scaffolded into 10 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 16.35 kilobases in length.

Oyster larvae used for ecosystem restoration benefit from increased thermal fluctuation

A bottleneck in restoring self-sustaining beds of the European oyster (Ostrea edulis) is the successful development and settlement of larvae to bottom habitats. These processes are largely governed by temperature but a mechanistic understanding of larval performance across ecologically relevant temperatures is lacking. We reared larvae at low (20–21 °C) and high (20–24 °C) fluctuating temperatures and applied short-term exposures of larvae to temperatures between 16 and 33 °C to assess vital rates and thermal coping ranges. Larval thermal preference was between 25 and 30 °C for both rearing treatments which corresponded with optimum temperatures for oxygen consumption rates and locomotion. Larvae had 5.5-fold higher settling success, however, when reared at the high compared to the low fluctuating temperatures. Higher mean and periods of increased temperature, as projected in a future climate, may therefore enhance recruitment success of O. edulis in northern European habitats.

Differential reaction norms to ocean acidification in two oyster species from contrasting habitats.

Ocean acidification (OA), a consequence of the increase in anthropogenic emissions of carbon dioxide, causes major changes in the chemistry of carbonates in the ocean with deleterious effects on calcifying organisms. The pH/PCO2 range to which species are exposed in nature is important to consider when interpreting the response of coastal organisms to OA. In this context, emerging approaches, which assess the reaction norms of organisms to a wide pH gradient, are improving our understanding of tolerance thresholds and acclimation potential to OA. In this study, we deciphered the reaction norms of two oyster species living in contrasting habitats: the intertidal oyster Crassostrea gigas and the subtidal flat oyster Ostrea edulis, which are two economically and ecologically valuable species in temperate ecosystems. Six-month-old oysters of each species were exposed in common garden tanks for 48 days to a pH gradient ranging from 7.7 to 6.4 (total scale). Both species were tolerant down to a pH of 6.6 with high plasticity in fitness-related traits such as survival and growth. However, oysters underwent remodelling of membrane fatty acids to cope with decreasing pH along with shell bleaching impairing shell integrity and consequently animal fitness. Finally, our work revealed species-specific physiological responses and highlights that intertidal C. gigas seem to have a better acclimation potential to rapid and extreme OA changes than O. edulis. Overall, our study provides important data about the phenotypic plasticity and its limits in two oyster species, which is essential for assessing the challenges posed to marine organisms by OA.

Comparative Description and Analysis of Oyster Aquaculture in Selected Atlantic Regions: Production, Market Dynamics, and Consumption Patterns

In the face of an increasing world population and a subsequent need for an increase in sustainable and healthy food production, low trophic species, such as oysters, emerge as a promising alternative. However, regional variations in oyster production techniques, market dynamics, and consumption patterns create challenges for both the global and local industry’s growth. In this study, a descriptive qualitative analysis of oyster markets across seven Atlantic regions was carried out. The Pacific oyster (Crassostrea gigas) was found to be farmed in most Atlantic regions except the US but is classified as invasive in Sweden and potentially invasive in South Africa. Other farmed and/or harvested species include native species (C. gasar and C. rhizophorae) in Brazil, the American cupped oyster (C. virginica) in the US, and the European flat oyster (Ostrea edulis) in France, Sweden, and the US. In Irish farms, Pacific oysters are primarily for export to European markets. The marine aquaculture sectors of Sweden, South Africa, and Namibia, as well as Brazil’s farming for C. gasar, were found to be underdeveloped. This study also observed a variation in licensing, property rights, and regulatory frameworks. Financial challenges for small businesses, ecological implications of seed production techniques, biosecurity risks, and public health considerations are emphasized as critical areas for attention. This study offers valuable insights into the selected markets and can serve as a useful resource for policymakers, aquaculture practitioners, and stakeholders in optimizing global shellfish industry strategies.

Understanding the influence of swarming timing on the dispersal of Ostrea edulis larvae in the Northern Adriatic Sea

Background Ostrea edulis, the European Oyster, is a key habitat engineering species, considered “functionally extinct” in much of its native range, however the presence of population patches, large enough to allow the recruitment of juveniles, is likely, at least in the Northern Adriatic Sea. In order to decide which areas to protect or enhance with substratum suitable for settlement, it is necessary to understand larval dispersal dynamics. The main research question was to understand how the settlement areas depends on the timing of swarming and on larvae emission location. Methods Larval dispersal modelling tools already exist, and for the purpose of this study the use of an open-source phyton model code ‘Opendrift’, parametrised for O. edulis larvae with specific parameters related to growth and speed of vertical movement, based on existing literature data. Necessary forcing functions (currents, temperature) were taken from Copernicus, and gridded bathymetry data was downloaded from GEBCO repository. Results The results of this preliminary model-based study showed that the settling areas depend on the timing of the emission periods, given that different emissions can lead to different time spent as plankton maturing to settlement, therefore potentially reaching further. Initial seeding location can also matter, due to differences in currents that could be encountered. Conclusions Some experimental validation should follow this modelling approach, including genetic analyses to verify sources, this setup using an open data and an open access existing modelling framework to predict larval settlement is promising in enabling the upscaling and application for restoration and conservation purposes in other areas.

A blue carbon model for the European flat oyster (Ostrea edulis) and its application in environmental restoration

Abstract Historically, considerations of the carbon budget of bivalve shellfish have disproportionately focused on the cycling of carbon in shell alone, overlooking respiratory release and the potential role of bivalve shellfish habitats in the stabilization of sediment, and therefore of carbon. Data on carbon cycling are key to providing essential evidence to inform evaluation of management strategies and the business case for restoration of European flat oyster (Ostrea edulis) habitats. The purpose of this study was to examine the flat oyster carbon budget at the scale of the individual and to set out a framework to enable future comparisons of carbon budgets between ecosystems. Through the combination of previously established work with measurements of calcification and respiration both in situ and ex situ, a carbon budget at the scale of a single oyster was determined. In consideration of the flat oyster carbon budget, the inclusion of the deposition of sedimentary carbon, as well as carbon stored in shell, balanced with the release of carbon through respiration and calcification suggests that these habitats are unlikely to be significant carbon sinks in the context of global climate change mitigation. However, the recovery of flat oyster beds is likely to facilitate the accretion of substantial carbon stocks that are nevertheless important in conservation management.

Impact of exposure temperature rise on mass mortality of tidal flat pacific oysters

Oysters are a major commercial and ecological fishery resource. Recently, the oyster industry has experienced mass mortality in summer due to environmental factors. Generally, the survival of oysters in aquatic environments is mainly impacted by environmental stressors such as elevated sea temperatures and reduced salinity; however, the stressors impacting tidal flat oysters that are repeatedly exposed to air remain poorly understood. Hence, we studied the relationship between environmental factors and the survival of tidal flat pacific oysters in Incheon, South Korea, where mass mortality is common. Principal component analysis and Bayesian networks revealed that air temperature (in spring and summer) and sea temperature (in summer) are related to oyster production. In habitats of the tidal flat oysters during the summer, high temperatures of 34.7–35.4°C (maximum 47.6°C) were observed for average durations of 0.8–1.9 hours (maximum 3.6 hours). Furthermore, heat waves occurred for up to 12 consecutive days. Results from the multiple stress test showed that when exposed to 45°C (air temperature) for 4 hours per day, the survival rate of oysters was 42.5% after only 2 days and 0% after 6 days. The findings stemming from the field observations and stress tests suggest that high temperatures during emersion may contribute to mass mortality of oysters in summer, indicating a potential threat to oysters due to climate change. To understand the effects of future thermal stress on oysters more accurately, simultaneous long-term trend analyses and field-based observations are required.

Characterized extracts of the tropical red seaweed Acanthophora spicifera protect Ostrea edulis larvae against Vibrio coralliilyticus

Vibriosis is one of the most common bacterial diseases affecting bivalve mollusk hatcheries, especially during their early life stages, leading to high mortality rates and significant economic losses worldwide. Bivalves are more susceptible to diseases because they are filter-feeding organisms capable of accumulating a wide diversity of microorganisms, antibiotic residues, and other contaminants present in the marine environment. In the present study, we evaluated the in vitro and in vivo bioactivity of the aqueous and ethanolic (10, 25, 50, 75, and 100%) extracts of the tropical red seaweed Acanthophora spicifera against Vibrio coralliilyticus which affects the larvae of the European oyster Ostrea edulis. The aqueous extract displayed 43.1% inhibition of V. coralliilyticus growth at 100 mg/L after 46 h (regrowth performance). During the toxicity test, O. edulis larvae showed a survival rate of 91.1 ± 5.8% and 84.6 ± 5.2% at aqueous extract concentrations of 1 and 5 mg/L, respectively. In the challenge test with V. coralliilyticus at a cell density of 105 cells/mL, the aqueous and 10, 25, and 50% ethanol (v/v) extracts at 1 mg/mL resulted in significantly higher survival rates (99.2 ± 1.0%, 93.3 ± 8.8%, 96.5 ± 0.9%, and 95.8 ± 1.9%, respectively) at 48 h post-challenge compared to only 0.6 ± 1.1% for the larvae challenged with Vibrio without seaweed extract (positive control). Chemical characterization of aqueous and 25% ethanol extracts, showing the highest bioactivity based on the challenge test, revealed the presence of succinic acid and the heterosides floridoside and digeneaside as major components in both extracts. This is the first report of the presence of digeneaside in A. spicifera. These findings suggest that aqueous and 25% ethanolic extracts from Acanthophora spicifera provide a natural alternative for disease management in O. edulis hatcheries.