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Pearl culture in Fiji relies on a supply of pearl oysters obtained through the strategic deployment of spat collectors. Although the design and deployment of spat collectors aim to maximize the recruitment of pearl oysters (Pinctada and Pterin spp.), this activity incidentally captures many other bivalves as bycatch. This study explored whether tropical rock oysters (specifically Magallana bilineata and Saecostrea spp.) were present and sufficiently abundant as bycatch from pearl oyster spat collectors, to support additional commercial opportunities. The results showed that the absolute (0.7 [+ or -] 2.1 spat collector-1) and proportional (2.9% of all bivalves) abundance of these taxa was very low, which would limit oyster harvest in meaningful quantities. Although the prospect of creating additional revenue streams from bycatch could be seen as an incentive to on-grow and sell tropical rock oysters despite their low abundance, it is argued that greater benefit would come from prioritizing activities related to pearl oysters and associated downstream products such as mabe pearl, shellcraft, and pearl-meat production. Ultimately, existing spat collection activities within the cultured pearl sector did not have the anticipated potential to support supplemental aquaculture of tropical rock oysters. KEY WORDS: Fiji, spat collection, fouling, bycatch, tropical rock oyster, Saecostrea, Magallana bilineata, INTRODUCTION Tropical rock oysters are excellent candidates for aquaculture (Angell 1986, Nowland et al. 2020). They are consumed almost everywhere they occur (M unro 1994, Kinch et al. 2019a, Simard [...]

[Display omitted] • Toxoplasma gondii DNA was detected in bivalves from the Kerguelen and Galapagos archipelagos. • Its occurrence differed between sampling sites in Kerguelen but not in Galapagos. • In both archipelagos, quantitative PCR-positive bivalves were found on islands without cats. • Our finding demonstrated the waterborne transport of oocysts over at least 20 km. • Exposure to currents and giant kelp density affect T. gondii detection in bivalves. Oocysts of the protozoan Toxoplasma gondii are found in felid feces and can be washed into coastal waters, where they persist for months, attaching to algae and accumulating in invertebrates. We used wild bivalves to assess contamination of coastal waters of the Kerguelen and Galapagos archipelagos by this zoonotic parasite. Additionally, we leveraged the contrasting situations of these archipelagos to identify some potential drivers of contamination. In the Galapagos, with a cat density reaching 142 per km2, 15.38% of the sampled oysters (Saccostrea palmula) tested positive for T. gondii by quantitative real-time PCR (qPCR) (n = 260), and positive samples were found in all eight sampling sites. In Kerguelen, with 1-3 cats per km2, 40.83% of 120 tested mussels (Mytilus edulis platensis) were positive, and positive samples were found in four out of the five sampling sites. These findings provide evidence of T. gondii contamination in the coastal waters of these archipelagos. Furthermore, T. gondii -positive bivalves were found on islands located 20 km away (Galapagos) and 5 km away (Kerguelen) from the nearest cat population, indicating that T. gondii oocysts can disperse through waterborne mechanisms over several kilometers from their initial deposition site. In the Galapagos, where runoff is infrequent and all sites are exposed to currents, the prevalence of qPCR-positive bivalves did not show significant variations between sites (p = 0.107). In Kerguelen where runoff is frequent and site exposure variable, the prevalence varied significantly (p < 0.001). The detection of T. gondii in Kerguelen mussels was significantly correlated with the site exposure to currents (odds ratio (OR) 60.2, p < 0.001) and the on-site density of giant kelp forests (OR 2.624, p < 0.001). This suggests that bivalves can be contaminated not only by oocysts transported by currents but also by consuming marine aggregates containing oocysts that tend to form in kelp forests. [ABSTRACT FROM AUTHOR]

Tetraploid oysters are valuable germplasm resources for the production of triploid oysters. However, the broodstock condition and gonadal development of tetraploid oysters are poorly understood. To assess the effects of temperature on gamete quantity and quality, tetraploid and diploid oysters were held at controlled temperatures of 18, 20 and 22 °C for 120 days. The gametogenesis process in tetraploid and diploid oysters showed an accelerated trend in response to increased conditioning temperatures. Nonetheless, the gonadal development of tetraploid oysters was slower than that of diploid oysters. Histomorphometric analysis of gonadal tissues showed variations in observed sex ratio under different conditioning temperatures. The proportions of tetraploid and diploid males increased with elevated temperature. However, survival rates of tetraploid and diploid oysters at 22 °C were significantly lower than those at 18 and 20 °C (P < 0.05). In terms of the number of oocytes and spermatozoa, tetraploid oysters were fewer than diploid oysters. Overall, these results demonstrated the differences in broodstock conditioning and gonadal development between tetraploid and diploid oysters, suggesting the need for specialized broodstock cultivation strategies for tetraploid oysters. [ABSTRACT FROM AUTHOR]

The quality of oysters is reflected by volatile organic components. To rapidly assess the freshness level of oysters and elucidate the changes in flavor substances during storage, the volatile compounds of oysters stored at 4, 12, 20, and 28 °C over varying durations were analyzed using GC-MS and an electronic nose. Data from both GC-MS and electronic nose analyses revealed that alcohols, acids, and aldehydes are the primary contributors to the rancidity of oysters. Notably, the relative and absolute contents of Cis-2-(2-Pentenyl) furan and other heterocyclic compounds exhibited an upward trend. This observation suggests the potential for developing a simpler test for oyster freshness based on these compounds. Linear Discriminant Analysis (LDA) demonstrated superior performance compared to Principal Component Analysis (PCA) in differentiating oyster samples at various storage times. At 4 °C, the classification accuracy of the optimal support vector machine (SVM) and random forest (RF) models exceeded 90%. At 12 °C, 20 °C, and 28 °C, the classification accuracy of the best SVM and RF models surpassed 95%. Pearson correlation analysis of the concentrations of various volatile compounds and characteristic markers with the sensor response values indicated that the selected sensors were more aligned with the volatiles emitted by oysters. Consequently, the volatile compounds in oysters during storage can be predicted based on the response information from the sensors in the detection system. This study also demonstrates that the detection system serves as a viable alternative to GC-MS for evaluating oysters of varying freshness grades. [ABSTRACT FROM AUTHOR]

In this study, microcapsules of Lactiplantibacillus plantarum 299V were prepared using an emulsification/internal gelation technique. Loads of the probiotics were condensed to 9.86 ± 0.13 log CFU/g after 24 h fermentation of the microcapsules. Physical characterization revealed that L. plantarum 299V cells were uniformly distributed within the core of the microcapsules, with a mean diameter of 109.81 ± 0.39 µm and a span value of 0.36 ± 0.00, which were comparable to those of the unfermented microcapsules (p > 0.05). The viability of L. plantarum 299V in the fermented microcapsules was 2.08 ± 0.15 log higher than that of free cells at the end of 5 h simulated gastrointestinal digestion (p < 0.05). Oysters were able to accumulate the fermented microcapsules through filter feeding, resulting in a load of probiotics exceeding 6.00 log CFU/g. The presence of L. plantarum 299V‐carrying microcapsules in oyster tissues significantly suppressed spoilage‐causing bacteria during 11 days refrigeration storage, suggested by the tested parameters, including total psychrotrophic bacteria, H2S‐producing bacteria, and Pseudomonas spp. (p < 0.05). Pathogenic bacteria, including Vibrio parahaemolyticus and Salmonella enterica artificially introduced into oysters, were also significantly suppressed by over 1.00‐log within 4 days compared to control samples (p < 0.05). In summary, oysters bioaccumulated with fermented L. plantarum 299V‐carrying microcapsules, justified a novel probiotic‐carrying product to exsert the health‐promoting effect of probiotics. This solution could also enhance the microbial quality and safety of oysters during storage. [ABSTRACT FROM AUTHOR]

Structural habitats support high biodiversity by providing refuge, forage resources, and recruitment habitat that upwardly influence the broader faunal community structure. However, there are few system-wide studies that empirically measure communities before and after major shifts in habitat structure or availability, limiting our ability to predict the consequences of changes in structural habitat above local scales. We used the collapse of the Apalachicola Bay, Florida oyster population as a natural experiment to assess the impacts of estuary-wide structural habitat loss on the nekton community through long-term faunal monitoring data. Habitat losses of this magnitude are expected to decrease diversity and alter composition, so we expected to observe these changes in Apalachicola Bay after the oyster population collapse. We assessed changes in Gini-Simpson diversity and composition over a 21-year period encompassing the 2012 oyster collapse using generalized linear mixed models to account for confounding drivers. We surprisingly found no evidence that Gini-Simpson diversity or composition differed immediately before or following the collapse, which may be explained if estuarine fauna were able to effectively use other habitats. This suggests that proportional changes in diversity or composition from loss or gain of structural habitats cannot be assumed at the system-wide scale. [ABSTRACT FROM AUTHOR]

Human noroviruses (HuNoVs), the most prevalent viral contaminant in food, account for a substantial proportion of nonbacterial gastroenteritis cases. Extensive work has been focused on the diagnosis of HuNoVs in clinical samples, whereas the availability of sensitive detection methods for their detection in food is lacking. Here, we developed a virus enrichment approach utilizing graphene-based nanocomposites (CTAB-rGO-Fe3O4) that does not rely on large instruments and is suitable for on-site food pretreatment. The recovery efficiency of the developed virus enrichment procedure for serially diluted GII.4 norovirus ranged from 10.06 to 72.67% in strawberries and from 2.66 to 79.65% in oysters. Furthermore, we developed a real-time recombinase polymerase amplification (real-time RPA) assay, which can detect as low as 1.22 genome copies µL−1 of recombinant plasmid standard and has no cross-reactivity with genomes of astrovirus, rotavirus, adenovirus, and MS2 bacteriophage. Notably, the combined virus enrichment and real-time RPA detection assay enhanced the detection limits to 2.84 and 37.5 genome copies g−1 in strawberries and oysters, respectively, compared to those of qPCR. Our strategy, the graphene-based virus enrichment method combined with real-time RPA, presents a promising tool for sensitively detecting HuNoVs in food samples. [ABSTRACT FROM AUTHOR]

The Pacific oyster (Crassostrea gigas Thunberg, 1795) is a crucial species in global aquaculture; however, optimizing larval survival rates and ensuring high-quality seed production continue to pose significant challenges. Probiotics have been investigated as a potential solution throughout various stages of the production process. This study assessed strains of lactic acid bacteria (LAB) and pathogenic strains isolated from oysters. Notably, several LAB strains, particularly Lactobacillus plantarum 69Cr, demonstrated probiotic potential by inhibiting the growth of pathogens such as Vibrio proteolyticus. In Pacific oyster larvae, the L. plantarum 69Cr strain significantly improved survival, with an increase of over 80% compared to those exposed to the pathogen Staphylococcus pasteuri. These findings highlight the effectiveness of the L. plantarum 69Cr strain as a promising probiotic for protecting oyster larvae from pathogenic threats. [ABSTRACT FROM AUTHOR]

Climate change and nutrient enrichment are increasing the frequency of algal blooms, with sometimes significant impacts on coastal ecosystems. Haslea ostrearia blooms have been documented in oyster ponds and are not harmful, yet their effects in open environments remain underexplored. Marennine, a blue pigment produced by H. ostrearia, can display a range of biological properties in laboratory conditions, including antibacterial and allelopathic properties. Other blue Haslea species, forming blooms, synthesize bioactive marennine-like pigments. This study aims to understand if and how these blooms could affect the underlying community of microorganisms living in the biofilms. Morphological and molecular techniques were used to assess community dynamics during bloom events. Our findings indicate that blue Haslea blooms do not significantly alter the diatom or bacterial populations. However, they are paired with enhanced alpha diversity in the microbial communities. These observations suggest a complex interaction between bloom events and microbial dynamics. Additionally, this study expands our understanding of the bioactive properties of marennine-like pigments and their ecological roles, suggesting new avenues for biotechnological applications. This work underscores the importance of further research into the environmental and biological implications of blue Haslea blooms. [ABSTRACT FROM AUTHOR]

For decades, many marine animals have been considered to exhibit cosmopolitan or transoceanic distribution. This situation is prevalent in Asia, where many species were collected and named by American or European experts in the 1700s to early 1900s. Using the windowpane oysters Placuna—a small genus of bivalves with five recognized species—we show that careful analysis is required to reassess the validity of these species. Currently, only two species of Placuna (P. placenta and P. ephippium) widely reported in the Indo‐Pacific region have been recorded from Chinese coastal waters. Here, we described two new species of Placuna from China. Placuna vitream sp. nov. can be distinguished from P. placenta by its larger ridge angle. Phylogenetic analysis using five gene fragments fully supported that P. vitream sp. nov. is a sister to the specimen from Singapore identified as P. placenta and more distant from other Placuna species with available molecular data. Besides, based on subfossil shells, we describe Placuna aestuaria sp. nov. that differs from its congeneric species by its broad hinge, medium ridge angle, and nearly straight ridges. Finally, we suggest a combination of hinge structure and ridge angle that can be used for identifying Placuna species and preparing a key to this genus. Our findings of two new species expand the diversity of Placuna and prompt reassessment of the many presumably widely distributed marine species in Asia. [ABSTRACT FROM AUTHOR]

Determining the efficacy of restoration practices is critical for enhancing and rebuilding degraded ecosystems. A fundamental question in marine restoration design is whether to employ active (e.g. using living plants or oysters that form the biogenic habitat) or passive (e.g. restoring the hydrology and sediment materials at the site) restoration strategies. Furthermore, the identity of sources used in restoring biogenic habitats could influence the effectiveness of restoration efforts. We present results from two independent experimental restoration efforts designed to explore the efficacy of these different approaches for the recovery of Crassostrea virginica (eastern oyster) reef habitat. Conducted from 2015–2020 in Rhode Island, USA, the restoration experiments compared 1) passive (unseeded shell) vs. active (seeded spat on shell) restoration methods in Ninigret Pond, and 2) restored reefs seeded with hatchery sourced vs. wild oyster lineages in Quonochontaug Pond. In Quonochontaug Pond, the hatchery-sourced line exhibited greater mortality than the wild lines. Restored reefs in both projects remained viable all four years post-restoration; however, low recruitment continues to limit the long-term sustainability of restored reefs in these Rhode Island systems. Natural mortality varied spatially within each coastal pond, ranging from 33–81% per year. Across both experiments, oyster mortality increased with rising temperature, salinity, and disease prevalence. Our results suggest that utilizing active restoration with spat spawned from multiple sources, including wild populations, may improve the success of oyster restoration. Future habitat restoration efforts should consider the environmental variability associated with restoration sites and the source of restoration species during project planning. [ABSTRACT FROM AUTHOR]

High-frequency recordings of valve opening behavior (VOB) in bivalves are often used to detect changes in environmental conditions. However, generally a single variable such as temperature or the presence of toxicants in the water is the focus. A description of routine VOB under non-stressful conditions is also important for interpreting responses to environmental changes. Here we present the first detailed quantitative investigation of the in-situ VOB of eastern oysters (Crassostrea virginica) to environmental variables typically not considered stressful. The VOB of eight individuals was monitored for seven weeks in a Louisiana estuary. We examined the relationships between VOB metrics (variance in mean % max opening among oysters, the probability of an oyster being closed, and the rate of valve closure), and temperature, salinity, chlorophyll-a (chl-a) concentration, the rate of change in those environmental variables, and the rate of change in water depth. Relationships were analyzed through statistical models including rates of change over 0, 0.25, 1-, 6-, 12-, and 24-hours. All the responses were best explained by the 12-hour time step model. The interaction effect between salinity and the rate of change of salinity had the greatest impact on variance in oysters' behavior. Oysters closed faster at higher salinities and were more likely to be closed at lower chl-a concentrations. Significant interactions were found between many environmental variables, indicating a high level of complexity of oyster behavior in the natural environment. This study contributes to a better understanding of the impact of environmental conditions on oyster behavior and can help inform predictive tools for restoration initiatives and fisheries practices. [ABSTRACT FROM AUTHOR]

Recycled Concrete Aggregate (RCA) of the chemical and biological effects must be understood to avoid potential adverse impacts to the bay's aquatic ecosystem. RCA application as a base material for oyster reefs did not adversely affect oyster spat growth and survival, or the surrounding environment. Evaluated RCA leaching for petroleum byproducts showed that RCA as a base material for oyster reefs did not leach any hydrocarbon chemicals, and no water extractable SVOC were detected. The research found potential RCA application to the Chesapeake Bay watershed as a bottom conditioning material for oyster aquaculture. Overall, the findings support the use of RCA for oyster aquaculture. [ABSTRACT FROM AUTHOR]

Shifts from saltmarsh to mangroves are well-documented at mangrove poleward boundaries. A regime shift from intertidal oyster (Crassostrea virginica) reefs to mangrove islands has recently been documented in transitional phases in Florida, USA. To understand the local drivers of an oyster/mangrove regime shift and potential tipping points leading to a permanent mangrove state, we tracked all mangrove propagules (n = 1681) across 15 intertidal oyster reefs with or without adult mangroves for 15 months in Mosquito Lagoon, FL. While no propagule bottleneck was observed, few (3.2%) mangrove propagules/seedlings survived on reefs with no prior encroachment, compared to 11.3% and 16.1% on reefs with established older (pre-1943) or newer (1943 to present) adult mangrove stands, respectively. In total, 90.6% of the arriving propagules were from the red mangrove Rhizophora mangle; 13.2% of these were alive at the end of this study. Survival was <1% for black (Avicenna germinans) and 0% for white (Laguncularia racemosa) mangroves. Factors that promoted red mangrove success included close proximity (≤0.3 m) to adult mangroves, especially black mangroves; partial, upright burial of propagules in sediment; and arrival on reefs after annual high-water season. Additionally, once reefs had 50% mangrove cover, the density of red mangrove seedlings increased from 0.04 to 0.46 individuals m−2. Although climate change has alleviated the impact of extreme freezes on mangroves, local factors determine whether the regime shift will be complete and permanent; positive feedback loops associated with established mangroves suggest mangrove recruitment on intertidal oyster reefs will continue to increase. [ABSTRACT FROM AUTHOR]

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Microplastic ingestion by marine organisms presents a challenge to both ecosystem functioning and human health. We characterized microplastic abundance, shape, size, and polymer types ingested by the West African mangrove oyster, Crassostrea tulipa (Lamarck, 1819) sampled from estuaries and lagoons from the Gambia, Sierra Leone, Ghana, Benin, and Nigeria using optical microscopy and Fourier transform infrared (FTIR) techniques. A total of 780 microplastics were isolated in the whole tissues of the 250 oysters (n = 50 oysters per country). The abundance and distribution of microplastics in the oysters followed the pattern: the Gambia > Ghana > Sierra Leone > Nigeria > Benin. The Tanbi wetlands in the Gambia recorded the highest average of 10.50 ± 6.69 per oyster while the Ouidah lagoon in Benin recorded the lowest average of 1.80 ± 1.90 per oyster. Overall, microplastic numbers varied significantly (p < 0.05) among the five countries. Microfibers, particularly those within 1001–5000 μm size, dominated the total microplastic count with a few fragments and films. No spherical microplastics were isolated in the oysters. In the Sierra Leone and Benin oysters, fragments and films were absent in the samples. Microplastic between the 1001 and 5000 μm size class dominated the counts, followed by 501–1000 μm, 101–500 μm, and 51–100 μm. Five polymer groups namely polyethylene, polyester, nylon, polypropylene, and polyamide were identified across the five countries, with polyethylene occurring in oysters from all five countries and polyester occurring in all but the oysters from Nigeria. This diversity of polymers suggests varied sources of microplastics ingested by the studied oysters. The absence of microspheres across the five supports findings from other studies that they are the least ingested and highly egested by the oysters. [ABSTRACT FROM AUTHOR]

Lysozyme, an antimicrobial agent, is extensively employed in the food and healthcare sectors to facilitate the breakdown of peptidoglycan. However, the methods to improve its catalytic activity and secretory expression still need to be studied. In the present study, twelve lysozymes from different origins were heterologously expressed using the Komagataella phaffii expression system. Among them, the lysozyme from the European flat oyster Ostrea edulis (oeLYZ) showed the highest activity. Via a semi-rational approach to reduce the structural free energy, the double mutant Y15A/S39R (oeLYZ dm) with the catalytic activity 1.8-fold greater than that of the wild type was generated. Subsequently, different N-terminal fusion tags were employed to enhance oeLYZ dm expression. The fusion with peptide tag 6×Glu resulted in a remarkable increase in the recombinant oeLYZdm expression, from 2.81 × 103 U mL–1 to 2.11 × 104 U mL–1 in shake flask culture, and eventually reaching 2.05 × 105 U mL–1 in a 3-L fermenter. The work produced the greatest amount of heterologous oeLYZ expression in microbial systems that are known to exist. Reducing the structural free energy and employing the N-terminal fusion tags are effective strategies to improve the catalytic activity and secretory expression of lysozyme. [Display omitted] • Lysozymes from different origins were expressed solubly in eukaryotic system. • Lysozyme from Ostrea edulis (oeLYZ) showed the highest activity. • The catalytic activity of the oeLYZ was improved via semi-rational design. • Peptide tag 6×Glu significantly facilitated the secretory expression of oeLYZ. • High-density fermentation production of oeLYZ was achieved. [ABSTRACT FROM AUTHOR]

Sustainable aquaculture includes the aquaculture of non-fed crops that provide ecosystem services including nutrient extraction and water quality improvement. While shellfish are the most farmed sustainable aquaculture crops in the USA, shellfish farmers in the northeastern US have an interest in diversifying their crops and incorporating seaweeds into their farms. In this study, we worked with oyster farmers to investigate the potential for farming sugar kelp, Saccharina latissima, across different environmental regimes in coastal Rhode Island USA. Kelp seed spools were outplanted at two time points in the fall/winter of 2017 and 2018 at four sites and cultivated until harvest the following spring. Kelp performance (length, width, yield), tissue content, and nutrient extraction were determined for each line in each year; oyster growth was also measured monthly for one year at each site. We found that kelp could successfully grow in both shallow coastal lagoons and estuarine sites, although the timing of planting and placement of sites was important. Lines that were planted earlier (as soon as water temperatures<15°C) grew longer and yielded more biomass at harvest; overall, kelp blade yield ranged from 0.36 ± 0.01 to 11.26 ± 2.18 kg/m long line. We report little variation in the tissue quality (C:N) of kelp among sites, but differences in biomass production led to differences in nutrient extraction, which ranged from 0.28 ± 0.04 to 16.35 ± 4.26 g nitrogen/m long line and 8.93 ± 0.35 to 286.30 ± 74.66 g carbon/m long line. We found extensive variability in kelp growth within and between lines and between years, suggesting that crop consistency is a challenge for kelp farmers in the region. Our results suggest that, as there is a lower barrier in terms of permitting (versus starting a new aquaculture farm), it may be a worthwhile investment to add sugar kelp to existing oyster farms, provided they have suitable conditions. At current market rates of US$0.88-$3.30 per kg, farmers in southern New England have the potential to earn US$2,229 per 60 m longline. While seaweed aquaculture is growing, considerable barriers still exist that prevent wide-scale kelp aquaculture adoption by existing aquafarmers. [ABSTRACT FROM AUTHOR]

Induced homologous tetraploid oysters are typically derived from a limited number of effective parents, with subsequent breeding steps likely to cause inbreeding, which may cause their own production performance to decline. To explore the performance of inbreeding, we established outbred (F0) and inbred lines (F1 and F2) in tetraploid Pacific oyster. Cleavage rate, shell height, survival rate, and total weight were compared. Inbreeding coefficients in F0, F1, and F2 were 0, 0.25, and 0.375, respectively. The results showed that there was no significant difference in cleavage rate between outbred line and inbred lines. The F1 showed distinct growth and survival depression only at larval stage, but no depression at grow-out stage. F1 growth and survival IDC values at larval stage were − 1.29% to 0.03% and − 0.31% to 0.01%, respectively. However, depressed growth and survival rate appeared in almost all F2 growth cycle; F2 growth and survival IDC values were − 1.10% to − 0.78% and − 3.14% to − 4.51% in larval stage and − 0.48% to − 0.25% and − 0.79% to − 0.64% in grow-out stage, respectively. Growth and survival rate at Longkou and Qingdao sites showed no depression in the F1 line during grow-out stage. The results indicate that inbreeding depressed growth and in particular survival in tetraploid oysters. With increased inbreeding levels, depressed growth and survival became more distinct. We provided important insights on the inbred lines construction and further breeding of tetraploid oysters. [ABSTRACT FROM AUTHOR]

Pacific oysters (Crassostrea or Magallana gigas) are one of the most economically important aquaculture species globally. Over the past two decades, ostreid herpesvirus (OsHV-1) has become a major pathogen of cultured Pacific oysters, resulting in widespread mortality with a global distribution. Experimental use of OsHV-1 is challenging for many reasons, including both complexity of host–pathogen dynamics and a lack of functioning model systems. The goal of this study was to improve the tools available for working with OsHV-1 in both whole animals and in tissue explants established from oysters maintained in controlled laboratory conditions. Tissue explants were taken from oysters originating from two different sources that have different levels of mortality in experimental OsHV-1 infections and were exposed to OsHV-1. A whole-animal infection experiment was run concurrently as a comparison. Quantitative PCR and electron microscopy were used to confirm that the explants were capable of replicating OsHV-1. Furthermore, the quantitative PCR results suggest that the source of the oysters was significant in determining the outcome of infection in the explants, supporting the validity of the explant model for OsHV-1 infection. This tissue explant approach for studying OsHV-1 allows for the control of confounding factors in the disease outcome that is not possible in whole-animal experiments, providing a new tool for the study of OsHV-1 in Pacific oysters. [ABSTRACT FROM AUTHOR]

Sentiment analysis, a form of data analytics, utilises information from online discussions, reviews, and social media posts to assess consumer sentiments. This study utilised data collected from social media using online listening procedures to assess online sentiments on oysters from January 2019 through December 2022. The analysis utilises machine learning algorithms to extract consumer sentiments, opinions, and demands from online chatter from different online domains. The online sentiments are determined as positive, negative, or neutral based on their word choice, tone, and context. The information provided gives insights into perception, which is valuable information for oyster producers, seafood industry stakeholders, and marketers to identify consumer preferences and formulate appropriate strategies accordingly. The results suggest that while farmed oysters are gaining popularity, there are still some concerns and criticisms around the industry. Positive words associated with mentions of oysters in general include 'great', 'love', 'delicious', 'enjoyed', and 'oyster bar', while negative words associated with oysters include 'water', 'raw oyster', 'bad', and 'not eat'. The overall percentage net sentiment associated with all oysters in the United States is positive at 63%. The net sentiment associated with wild oysters is positive, at 51%, and that of farmed oysters is 58%. The oyster industry could invest more in public education, sustainability, and water‐cleaning initiatives to improve its image. Utilising social media to monitor and shape public perception can help the industry address concerns and enhance oyster‐related sentiments, offering valuable insights for marketing and sales strategies. [ABSTRACT FROM AUTHOR]

The depth culture influence (4, 8, and 16 m) and periods (upwelling and non-upwelling) on growth and survival of the pearl oyster Pinctada imbricata during 10 months in the southeastern Caribbean Sea (Cariaco Gulf) were evaluated. Monthly records were taken of survival, body growth, and fouling organisms of the pearl oyster, as well as weekly samples of the temperature, chlorophyll a, and seston of the water culture site. Monthly survival was above 92% at all depths. The variation in shell size and tissue mass of the oysters cultivated in the different depths showed a similar pattern, with slow growth during the non-upwelling period (June–October) and progressive growth during the upwelling period (November–April). The multivariate analysis showed that oyster growth was associated with the phytoplankton biomass at different depths, particularly during the upwelling period. Oysters at 4 m showed the greatest increases in all growth parameters, exceeding the minimum commercial size (50 mm) in 7 months. Hence, it is recommended that the culture of P. imbricata in the Gulf of Cariaco be started right before the upwelling season to take advantage of the high amount of food available during this period. It is also recommended that the suspended culture should not exceed 8 m for higher growth performance. [ABSTRACT FROM AUTHOR]

The Pacific oyster, Crassostrea gigas, is an important cultured species in the northern coastal areas of China. In recent years, the triploid oyster was popular worldwide because of its fast growth and high meat quality and has rapidly occupied a large portion of the oyster market. As a multi-generation selection strain, "Haida No.2" of C. gigas has good growth performance. At the same time, we have successfully obtained the triploid and tetraploid "Haida No.2." This study was conducted to evaluate the performance of the triploid of "Haida No.2" under different rearing environments. The results showed that there was no significant difference in fertilization rate and hatching rate between diploids and triploids, and so did the survival rate at the larval stage, while the cumulative survival rate of triploids was significantly lower than that of diploids. At grow-out stage, the growth and survival rate of triploids were significantly higher than diploids on day 420 at two sites; meanwhile, the triploid rate was slight decline but still kept a high level (96–98%) on 420 days at two sites. However, high gametogenesis and subsequent mass spawning of triploid females were observed at two sites (32% at Rongcheng and 54% at Rushan), and the fecundity of triploid females relative to diploid females was high (23.73% at Rongcheng and 41.15% at Rushan) under different rearing environments. Our results showed that the triploid of "Haida No.2" had better performance at grow-out stage than diploids. However, the phenomenon of high gametogenesis of triploid and spawning is not favorable for the industrialization of triploid oysters, and the mechanism of high gametogenesis of triploids needs further study. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS) are known to bioaccumulate in aquatic organisms, such as shellfish, and have been linked to adverse human health outcomes. Increasing attention has been focused on method development for the detection of PFAS in various media; however, these methods are typically tedious, require high solvent volumes, and are time consuming. The present method used a Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction approach and analysis by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) to detect 28 PFAS in Eastern oyster (Crassostrea virginica) tissue. This method was validated using limit of detection, limit of quantitation, and precision and accuracy studies. Limits of detection ranged from 0.2 to 5.8 ng g−1, limits of quantitation ranged from 0.66 to 19.2 ng g−1, and recoveries spanned 52.1–105.9% at the 100 ng mL−1 analyte level. Analysis of 12 unknown oyster composite samples revealed the detection of PFHxA, PFPeS, PFOA, PFHpA and PFOS and at least two compounds were detected in each oyster sample. This validated method proved to be an efficient and environmentally friendly sample preparation method for PFAS analysis in complex tissue media, such as oysters. [ABSTRACT FROM AUTHOR]

The Pacific oyster (Crassostrea gigas) has been cultured for its flesh in the Seto Inland Sea, western Japan, over the last half‐century. Its production has been reported as 'fluctuating', yet little is known about changes in oyster growth performance throughout long‐term culturing in this locality. To effectively manage oyster production under future environmental challenges, this study investigated the long‐term environmental influences on oyster growth performance. Environmental data and oyster biological data were obtained from observations in Hinase waters, Seto Inland Sea, and compared for the two periods 1990 and 2015–2021. Water temperature has not significantly changed in this locality during the oyster culturing period. Lower salinity was found in July of 2015–2021 due to heavy seasonal rainfall, which had a negative impact on oysters, specifically on survival rate and total weight. A high growth rate and high meat weight at harvest were found in the individuals cultured during the period 2015–2021, yet oyster total weight showed no significant difference. Further research on shell characteristics is required to have a better understanding of oyster growth characteristics. [ABSTRACT FROM AUTHOR]

Abstract Background In bivalves, the rate at which organisms grow is a major functional trait underlying many aspects of their commercial production. Growth is a highly polygenic trait, which is typically regulated by many genes with small to moderate effects. Due to its complexity, growth variability in such shellfish remains poorly understood. In this study, we aimed to investigate differential gene expression among spat of the pearl oyster Pinctada margaritifera with distinct growth phenotypes. Results We selected two groups of P. margaritifera spat belonging to the same F2 cohort based on their growth performance at 5.5 months old. Transcriptome profile analysis identified a total of 394 differentially expressed genes between these Fast-growing (F) and Slow-growing (S) phenotypes. According to functional enrichment analysis, S oysters overexpressed genes associated with stress-pathways and regulation of innate immune responses. In contrast, F oysters up-regulated genes associated with cytoskeleton activity, cell proliferation, and apoptosis. Analysis of genome polymorphism identified 16 single nucleotide polymorphisms (SNPs) significantly associated with the growth phenotypes. SNP effect categorization revealed one SNP identified for high effect and annotated for a stop codon gained mutation. Interestingly, this SNP is located within a gene annotated for scavenger receptor class F member 1 (SRF1), which is known to modulate apoptosis. Our analyses also revealed that all F oysters showed up-regulation for this gene and were homozygous for the stop-codon mutation. Conversely, S oysters had a heterozygous genotype and a reduced expression of this gene. Conclusions Altogether, our findings suggest that differences in growth among the same oyster cohort may be explained by contrasted metabolic allocation between regulatory pathways for growth and the immune system. This study provides a valuable contribution towards our understanding of the molecular components associated with growth performance in the pearl oyster P. margaritifera and bivalves in general.

Abstract Background The global dissemination of critical-priority carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) via food sources represents a significant public health concern. Epidemiological data on CR-hvKp in oysters in Egypt is limited. This study aimed to investigate the potential role of oysters sold in Egypt as a source for carbapenem-resistant K. pneumoniae (CRKP), hypervirulent K. pneumoniae (hvKp), and CR-hvKp and assess associated zoonotic risks. Methods A sample of 330 fresh oysters was randomly purchased from various retail fish markets in Egypt and divided into 33 pools. Bacteriological examination and the identification of Klebsiella pneumoniae were performed. Carbapenem resistance in K. pneumoniae isolates was determined by phenotypic and molecular methods. Additionally, the presence of hypervirulent K. pneumoniae was identified based on virulence gene markers (peg-344, rmpA, rmpA2, iucA, and iroB), followed by a string test. The clustering of CR-hvKp strains was carried out using R with the pheatmap package. Results The overall prevalence of K. pneumoniae was 48.5% (16 out of 33), with 13 isolates displaying carbapenem resistance, one intermediate resistance, and two sensitive. Both carbapenem-resistant K. pneumoniae and carbapenem-intermediate-resistant K. pneumoniae strains exhibited carbapenemase production, predominantly linked to the bla VIM gene (68.8%). HvKp strains were identified at a rate of 62.5% (10/16); notably, peg-344 was the most prevalent gene. Significantly, 10 of the 13 CRKP isolates possessed hypervirulence genes, contributing to the emergence of CR-hvKp. Moreover, cluster analysis revealed the clustering of two CR-hvKp isolates from the same retail fish market. Conclusion This study provides the first insight into the emergence of CR-hvKp among oysters in Egypt. It underscores the potential role of oysters as a source for disseminating CR-hvKp within aquatic ecosystems, presenting a possible threat to public health.

Abstract The Late Cretaceous was a time of high eustatic sea level that enabled extensive epicontinental seaways and carbonate platforms across the Tethyan Realm, providing favorable habitats for oyster communities to flourish. This study focuses on the Campanian Tethyan oysters from the North Eastern Desert of Egypt regarding taxonomy, palaeoecology, and palaeobiogeography. Three oyster species, Nicaisolopha nicaisei (Coquand, 1862), Pycnodonte (Phygraea) vesicularis (Lamarck, 1806), and Ambigostrea bretoni (Thomas and Peron, 1891), were identified from the Campanian succession in two studied sections. The sampled specimens of the genus Nicaisolopha have undergone a systematic palaeontological revision. As a result, N. tissoti (Thomas and Peron, 1891) is considered herein a junior synonym of N. nicaisei (Coquand, 1862). Palaeobiogeographically, the likely primary migration pattern of the studied oysters suggests an east–west trend along the Southern Tethys margin. All identified oysters in this study exhibit a Tethyan affinity and are primarily abundant in two main provinces: the Southern Tethys and the Western Tethys. The macrofaunal contents are categorized into two fossil associations: the Nicaisolopha nicaisei association of the middle-late Campanian age and the Pycnodonte vesicularis association of the late Campanian age. These macrofaunal associations indicate a deepening trend during the middle-late Campanian age, suggesting a transition from shallow inner neritic to middle neritic environments. Additionally, it is observed that Pycnodonteinae tend to grow larger under eutrophic conditions, low-energy environments, and nutrient-rich waters with high carbonate contents.

Background: In bivalves, the rate at which organisms grow is a major functional trait underlying many aspects of their commercial production. Growth is a highly polygenic trait, which is typically regulated by many genes with small to moderate effects. Due to its complexity, growth variability in such shellfish remains poorly understood. In this study, we aimed to investigate differential gene expression among spat of the pearl oyster Pinctada margaritifera with distinct growth phenotypes. Results: We selected two groups of P. margaritifera spat belonging to the same F2 cohort based on their growth performance at 5.5 months old. Transcriptome profile analysis identified a total of 394 differentially expressed genes between these Fast-growing (F) and Slow-growing (S) phenotypes. According to functional enrichment analysis, S oysters overexpressed genes associated with stress-pathways and regulation of innate immune responses. In contrast, F oysters up-regulated genes associated with cytoskeleton activity, cell proliferation, and apoptosis. Analysis of genome polymorphism identified 16 single nucleotide polymorphisms (SNPs) significantly associated with the growth phenotypes. SNP effect categorization revealed one SNP identified for high effect and annotated for a stop codon gained mutation. Interestingly, this SNP is located within a gene annotated for scavenger receptor class F member 1 (SRF1), which is known to modulate apoptosis. Our analyses also revealed that all F oysters showed up-regulation for this gene and were homozygous for the stop-codon mutation. Conversely, S oysters had a heterozygous genotype and a reduced expression of this gene. Conclusions: Altogether, our findings suggest that differences in growth among the same oyster cohort may be explained by contrasted metabolic allocation between regulatory pathways for growth and the immune system. This study provides a valuable contribution towards our understanding of the molecular components associated with growth performance in the pearl oyster P. margaritifera and bivalves in general. [ABSTRACT FROM AUTHOR]

This study examined heavy metals in some aquatic organisms [crabs (Callinectes amnicola), periwinkles (Tympanotonus fuscatus) and oysters (Crassostrea gasar)] from Eyaa Creek, Onne, in southern Nigeria. Samples were collected from four stations monthly for three months. Characterization of the environment was via physico-chemical properties, while heavy metal analysis was by Atomic Absorption Spectrometry. Physico-chemistry results indicated: temperature; 30.2 - 30.7oC; pH: 6.7 - 6.8; dissolved oxygen: 6.1 - 6.3 mg/l; electrical conductivity: 18.8 - 20. 8 mS/cm; total dissolved solids: 4698.5 - 6212.0 mg/l; salinity: 11.1 - 12.4 PSU and turbidity: 3.7 - 4.7 NTU. ANOVA showed insignificant difference (p>0.05) between stations indicating homogeneity of the area assessed. Mean metal concentrations (mg/kg) in the organisms were cadmium: 0.18 ± 0.09 - 0.60 ± 0.08; chromium: 0.41 ± 0.14 - 0.78 ± 0.08; iron: 12.1 ± 6.9 - 20.2 ± 7.7; lead: 0.31 ± 0.2 - 0.91 ± 0.05. Chromium and lead values were above permissible values of FAO/WHO and EU but cadmium fell within and above the limits. Principal component analysis did not show a clear pattern with organisms' feeding habit but discriminated based on metal concentrations. In conclusion metal concentration in periwinkles>crabs>oysters which was related to their feeding habits in terms of sediment and pelagic affiliations. [ABSTRACT FROM AUTHOR]

Marine molluscan cell lines, required for virus screening and cultivation, form essential tools for developing health management strategies for these animals in the blue economy. Moreover, they are also crucial to develop cultivated seafood. As there is no valid marine molluscan cell line, primary cell cultures are relied upon for all investigations. A sound protocol for generating primary cell cultures from molluscs is entailed, but existing protocols often involve heavy antibiotic usage and depuration that invariably affect gene expression and cell health. This work presents an easy‐to‐adopt, time‐saving protocol using non‐depurated mollusc Crassostrea madrasensis, which requires only initial antibiotic treatment and minimal exposure or no use of antibiotics in the cell culture medium. The important experimental considerations for arriving at this protocol have been elucidated. Accordingly, sodium hypochlorite and neomycin sulfate were chosen for disinfecting tissues. The study is the first to use shrimp cell culture medium (SCCM) as a cell culture medium for molluscan cell culture. Despite being osmoconformers, the oysters exhibited stable intracellular osmotic conditions and pH, which, when provided in vitro, promoted effective cardiomyocyte formation. The cell viability could be enhanced using 10% fetal bovine serum (FBS), but healthy cell culture could also be obtained using SCCM without FBS. The optimized culture conditions allowed for regular beating cardiomyocyte clusters that could be retained for a month. Limited cell proliferation, as shown by the BrdU assay, demands further interventions, such as possibly producing induced pluripotent stem cells. The optimized protocol and culture conditions also align with some requirements for producing cultivated meat from marine molluscs. [ABSTRACT FROM AUTHOR]

Crassostrea (Magallana) saidii has been commercially ranched in Malaysia and consumed for more than 160 years, but it was only recently identified as a new species to science. This study was conducted to evaluate the reproductive phenology of C. (M.) saidii. Samples of 30 individual oysters were taken monthly for 15 months from the sole population at Sungai Muar estuary in Johor, Malaysia. The sex ratio was 1:1.64 (male:female) for all examined specimens, with female numbers significantly higher. Hermaphrodism was detected in 1.56% of all samples. Spawning peaks in April (2019) and November (2018 and 2019), and were positively associated with the increased rainfall upstream. Gametogenesis occurred throughout the research period with temporal variations. The highest values of maturity index (MI) were recorded in March, August and October 2019, when most oysters were in matured and maturing stages. Condition index (CI) ranged from 31.90 ± 1.25 (April 2019) to 70.03 ± 3.23 (October 2019), exhibiting two peaks (March and October 2019) and subsequently reduced in CI indicating spawning consistency with histological observations. Anthropogenic stressors such as heavy sedimentation and inland development are threatening the survival of this species. The understanding of their reproductive biology is essential to ensure the survival and sustainability of C. (M.) saidii fishery. [ABSTRACT FROM AUTHOR]

Brett, J.; Samuell, M.; Augstein, B.; Parra, S.; Hancock, E.; Saunders, C.; Wunsch, S.; Winstead, N., and Boothby, J., 2024. Nature-based coastal protection: Measuring and modeling flow reduction by oysters. Journal of Coastal Research, 40(4), 647–660. Charlotte (North Carolina), ISSN 0749-0208. Natural coastal infrastructure protects coast lines from climate hazard impacts, such as erosion and flooding. Laboratory and modeling studies presented here examine the utility of oyster reefs as a form of natural coastal protection. Oyster reefs are known to provide both water quality improvements and erosion protection. Experiments were conducted to determine the effects of oysters on flow parameters in a recirculating flow channel. A cage of eastern oysters, Crassostrea virginica, was placed in the flow channel, blocking a portion of the flow, to imitate cultured oysters in the ocean. Particle image velocimetry was used to measure the flow behind the oyster cage to examine the impact of the oysters compared with a control test with an empty cage. Average velocities were reduced by 15%, with velocities directly behind the cage reduced 70% in fresh water and reversed in salt water. A setup similar to the laboratory experiments was simulated in a Coupled Ocean–Atmospheric–Wave–Sediment Transport (COAWST) model. In the COAWST model, the oyster reef was simulated as stiff vegetation with a drag coefficient of 8, reproducing the 70% reduction measured in the lab experiments. Finally, a regional model is presented, which demonstrates the impact of an oyster reef on waves and currents at a larger scale with a drag coefficient of 1.5, the highest numerically stable value found. Within the oyster vegetation patch, depth-averaged currents were reduced 14% and bottom currents were reduced 97%. Significant wave heights were reduced by 62% above the reef and 23% shoreward of the reef. The results here suggest that regional modeling such as COAWST can be an effective tool for assessing the impact of potential coastal resilience strategies to mitigate climate hazard impacts in a climate-changed world. [ABSTRACT FROM AUTHOR]

Native Olympia oysters (Ostrea lurida) occur in remnant natural populations throughout San Francisco Bay (SFB), California, United States, where managers have been working to restore oysters since 2002. Environmental conditions vary substantially along the estuarine gradient in the bay, such that oysters are exposed to different stressors in different locations and years. We monitored oysters that naturally recruited to experimental restoration substrates over 10 years at two sites on this gradient. We found that recruitment rates and adult densities varied over time and had different trajectories at the study locations. We found gradients in predation, space competition, and physical stressors between sites and along a tidal elevation span that corresponded with differences in adult densities. We documented mass mortality resulting from an extreme low‐salinity event at one site and subsequent recovery later that year. Our results, combined with data from natural populations at multiple sites, suggest that restoration outcomes within SFB could be improved by building and strengthening a connected portfolio of sites that are not simultaneously exposed to the same stressors. We recommend siting restoration projects across locations that represent a range of environmental conditions but that are sufficiently close for larval exchange. Unlike typical restoration approaches that use site selection to identify the best locations, the portfolio approach, just like the economic investment principle, would employ a diversity of environmental conditions. Because these environmental conditions can change over time, this approach can reap the greatest rewards over the long run precisely because of that diversity. [ABSTRACT FROM AUTHOR]

Functionally extinct ecosystems, those that have been locally eradicated save for remnant individuals, are unlikely to naturally recover over meaningful human time frames. However, ecosystem restoration provides opportunities to reverse functional extinction by rapidly addressing the physical and/or biological barriers that prevent natural recovery. Here, we assess the restoration progress of a native Flat oyster (Ostrea angasi) reef ecosystem in South Australia that was eradicated from the Australian mainland approximately 100 years ago. In the absence of any reference Flat oyster ecosystems in the region, restoration progress was assessed relative to ecological targets informed by a combination of local rocky reef ecosystems and an interim Flat oyster reference model informed by Australia's sole remaining O. angasi reef, in Tasmania. Two and half a years after the restoration was initiated via the construction of 14 boulder reefs, we observed densities of restored native adult O. angasi (192 ± 19 m−2; mean ± 1 SE) that exceeded oyster densities observed on the sole remaining natural reef. Communities of macroinvertebrates on the reef restoration represented approximately 60% of the biodiversity observed on healthy rocky reef reference systems, while ecological functions (e.g. filter feeding) are demonstrably increasing. The rate of recovery of this benthic ecosystem, from functionally extinct to a restored Flat oyster reef ecosystem within several years, demonstrates the latent resilience of degraded oyster communities and the capacity for effective marine restorations to achieve rapid ecological recoveries. [ABSTRACT FROM AUTHOR]

Optimizing habitat restoration success requires understanding how restoration location and design enhance the persistence and function of a restored habitat. Particular attention to the configuration of structure and its interaction with landscape‐scale processes is critical for enhancing the habitat value of restored areas. We monitored six subtidal restored oyster reefs in Pamlico Sound, North Carolina, United States, to identify how oyster demographics responded to initial habitat characteristics (e.g. reef area, volume, vertical relief, and perimeter‐to‐area ratio) and how changes in habitat characteristics over time altered suitability for oysters. Changes in reef habitat were measured by repeated mapping using bathymetric and side‐scanning sonar systems. A 2‐year time series of oyster demographic data quantified oyster response to habitat changes over time. All reefs provided habitat for the settlement and growth of oysters. Within 2 years of restoration, relative differences in oyster recruitment and survival emerged and were related to variations in reef location and two‐dimensional habitat characteristics among reefs, namely reef area and perimeter‐to‐area ratio. Larger reefs that were less fragmented resisted burial from sedimentation and enhanced oyster densities and biomass relative to smaller, more fragmented reefs that became heavily sedimented and failed to support oyster recruitment and survival. Positive feedback mechanisms between habitat characteristics and oyster recruitment success were established within 1 year of restoration and were likely driven by landscape‐scale processes such as sediment dynamics and larval supply. To improve restoration success, we recommend creating larger reef surfaces with low perimeter‐to‐area ratios in areas that promote habitat persistence. [ABSTRACT FROM AUTHOR]

In the United States, restoring oyster reefs is increasingly a priority, due to a desire to return the economic, ecological, and social services the habitat can provide. This growing demand for oyster reef restoration has led to the development of an oyster reef restoration economy. This study was the first to assess it as such, by using similar approaches to private sector market studies. Here, we conducted a market assessment to: quantify the market size in terms of annual dollars spent on oyster reef restoration projects; understand the variation in industry members involved, and market variation by region and state; analyze the distribution of the total market size across the value chain; and document primary factors that will contribute to future market growth or decline. We also used the direct annual spend to estimate the industry's impact on jobs, indirect output, and induced output from the oyster restoration industry on the U.S. economy. In the United States, the oyster reef restoration industry's overall size, measured as annual spend, is $70–90 M, directly supporting an estimated 1500 jobs and contributing $210 M of economic output. Most of the market is directed toward projects whose intended direct result is increased oyster populations versus planning, surveys, or monitoring. The vast majority (85%) of the market resides in the mid‐Atlantic and the Gulf of Mexico regions. Practitioners nearly unanimously agree that the oyster reef restoration industry will continue to grow over the next 5 years. [ABSTRACT FROM AUTHOR]

Ostrea chilensis (a flat oyster) is native to Chile and New Zealand. In Chile, this oyster has been cultured and harvested for at least 80 years. However, the culture of flat oysters has not developed like other aquaculture activities in Chile, mainly due to the inefficiency of the collectors (made of ribbed mussel shells) and the lack of spats produced. The objective of this study was to determine the capacity of spat collectors for the settlement of O. chilensis. For this purpose, field and laboratory experiments were carried out. Our results indicated that oyster larvae do not have a preference for either side of the shell (periostracum or nacreous) to settle on. However, after one year of growth in the field, juveniles were more abundant on the nacreous side of the shell (spat collector). Also, the oysters that settled on the nacreous side of the valve were larger. This was due to the fact that the periostracum had a greater number of epibionts, and they competed for space and resources with the settled oyster spats, causing a decrease in the abundance of oyster spats on that surface. Our findings raise the possibility that collectors could improve efficiency in the production of spats. Finally, we discuss the implications of these results for the Chilean oyster-farming industry. [ABSTRACT FROM AUTHOR]

Heat stress has received growing concerns regarding the impact on seafood quality. However, the effects of heat stress on the sensory properties of seafood remain unknown. In this study, the sensory properties of fresh oyster (Crassostrea ariakensis) treated with chronic heat stress (30 °C) for 8 weeks were characterized using electronic nose, electronic tongue, sensory evaluation, HS–SPME–GC–MS, LC–MS and transcriptomics. Overall, chronic heat stress reduced the overall sensory properties of oysters. The metabolic network constructed. based on enrichment results of 423 differential metabolites and 166 differentially expressed genes, showed that the negative effects of chronic heat stress on the sensory properties of oysters were related to oxidative stress, protein degradation, lipid oxidation, and nucleotide metabolism. The results of the study provide valuable insights into the effects of heat stress on the sensory properties of oysters, which are important for ensuring a sustainable supply of high-quality seafood and maintaining food safety. [ABSTRACT FROM AUTHOR]

Suspended oysters employ physiological strategies to adjust their metabolic needs with the available food resources. Using the biodeposition method, the feeding and processing behavior of Pacific oysters (Crassostrea gigas) was investigated with a field study comparing four periods (May, July, October, and December 2016) with different upwelling intensities in the coastal lagoon of San Quintin Bay (Mexico). We calculated physiological feeding responses throughout the culture cycle, including the clearance rate (CR), filtration rate (FR), net organic ingestion rate (NOIR), net organic absorption rate (NOAR), net organic selection efficiency, net absorption efficiency, and the ammonium excretion rate (AER). The dietary quality predictors showed large fluctuations in terms of total particulate material, organic fraction of seston, and chlorophyll concentration. Unlike the pumping activity, FR, NOIR, and NOAR were related to upwelling conditions, and C. gigas removed twofold, ingested fourfold, and assimilated fivefold more of the organic suspended material during the upwelling season compared with periods of weak upwelling. C. gigas showed the potential of depositing nearly twice the organic biodeposits to the sediments during the intense upwelling events. The highest AER was recorded in July and October, suggesting that seasonal temperature variation is the most important exogenous factor regulating nitrogen metabolism, even in a subtropical environment. Also, mechanistic models incorporating dietary quality predictors to the feeding and processing response functions of C. gigas were performed. We conclude that coastal upwelling plays an important bottom-up control on oysters' feeding and processing activity, and our results facilitate further studies of the carrying capacity of embayments influenced by eastern boundary current systems. [ABSTRACT FROM AUTHOR]

The marine environment faces continuous anthropogenic pressures, including infrastructural developments at a global scale. Integration of nature-inclusive measures in the design of infrastructural development is increasingly encouraged, but a lack of coordination results in fragmentation of projectbased measures, failing to meet the desired overall effects. To realize impact at system-scale, i.e. the seascape dimension required to achieve the set objective for a selected ecosystem component, overarching policies with shared targets towards effective nature-inclusive marine infrastructure are needed. We present a stepwise approach to work towards operational objectives for promoting selected ecosystem components that can be species, habitats or ecosystem processes, in which ruling policies, environmental conditions and the use of infrastructural development are aligned, and agreement on achievable ambitions is reached. Having clear targets will provide guidance to project developers in designing the infrastructure nature-inclusive, and in setting up relevant monitoring programs to evaluate the measures taken. We demonstrate how this stepwise approach could be applied to derive operational objectives for the design of nature-inclusive marine infrastructure in the context of offshore windfarm development in the North Sea, currently one of the most prominent infrastructure developments that changes the marine environment drastically. The European flat oyster Ostrea edulis has been selected as target species in the case study, as its once abundant population is now nearly extinct from the North Sea due to human disturbances, and there's growing interest to restore its reefs. The application of the stepwise approach indicates the potential for oyster reef restoration in the area, based upon a clear match between ruling policy, environmental conditions, and habitat suitability within offshore wind farms. An agreement between the main stakeholders on achievable ambitions can likely be established and would translate into the operational objective to actively introduce oysters to reach an initial critical mass and optimize settlement habitat in all future offshore wind farms in an area with suitable habitat characteristics. Such an agreement on overarching objectives is crucial to align separate initiatives to promote targeted ecosystem components and to jointly become most effective, which is ultimately in the best interest of the larger community using the system. [ABSTRACT FROM AUTHOR]

Background: The global dissemination of critical-priority carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-hvKp) via food sources represents a significant public health concern. Epidemiological data on CR-hvKp in oysters in Egypt is limited. This study aimed to investigate the potential role of oysters sold in Egypt as a source for carbapenem-resistant K. pneumoniae (CRKP), hypervirulent K. pneumoniae (hvKp), and CR-hvKp and assess associated zoonotic risks. Methods: A sample of 330 fresh oysters was randomly purchased from various retail fish markets in Egypt and divided into 33 pools. Bacteriological examination and the identification of Klebsiella pneumoniae were performed. Carbapenem resistance in K. pneumoniae isolates was determined by phenotypic and molecular methods. Additionally, the presence of hypervirulent K. pneumoniae was identified based on virulence gene markers (peg-344, rmpA, rmpA2, iucA, and iroB), followed by a string test. The clustering of CR-hvKp strains was carried out using R with the pheatmap package. Results: The overall prevalence of K. pneumoniae was 48.5% (16 out of 33), with 13 isolates displaying carbapenem resistance, one intermediate resistance, and two sensitive. Both carbapenem-resistant K. pneumoniae and carbapenem-intermediate-resistant K. pneumoniae strains exhibited carbapenemase production, predominantly linked to the blaVIM gene (68.8%). HvKp strains were identified at a rate of 62.5% (10/16); notably, peg-344 was the most prevalent gene. Significantly, 10 of the 13 CRKP isolates possessed hypervirulence genes, contributing to the emergence of CR-hvKp. Moreover, cluster analysis revealed the clustering of two CR-hvKp isolates from the same retail fish market. Conclusion: This study provides the first insight into the emergence of CR-hvKp among oysters in Egypt. It underscores the potential role of oysters as a source for disseminating CR-hvKp within aquatic ecosystems, presenting a possible threat to public health. [ABSTRACT FROM AUTHOR]

Habitat restoration efforts are often limited by cost, making it important that available funds are used efficiently and effectively to achieve desired restoration goals. In this study, we evaluate habitat provision for oysters and motile epifauna on restored oyster reefs in a northwestern Gulf of Mexico estuary constructed with discrete high vertical relief (~0.6m "reef mounds") or continuous low vertical relief (<0.08 m "reef flats"). Habitat provision on reef mounds exceeded that on reef flats within one month of construction and supported 0.75x higher oyster density, 2x higher motile epifauna biomass, and 3.6x higher motile epifauna density one year after construction. Oyster density on reef mounds remained relatively high throughout the study period, with ~2x higher oyster densities than reef flats 18 months after construction and ~1.5x higher oyster densities by the end of the study. Both reef mounds and reef flats increased oyster and epifaunal densities compared to unrestored areas. Although on-reef oyster densities were higher on reef mounds than reef flats, the total restored oyster areal density and volumetric density was higher in restored reef flat areas, primarily because the restored flats area had no gaps within its restoration boundaries. Our findings have practical value for better predicting restoration outcomes and achieving desired restoration goals based on restored oyster reef height, with reef mounds maximizing on-reef oyster and epifaunal densities and reef flats maximizing the total number of oysters per area restored or volume of substrate purchased. Understanding the benefits and tradeoffs between restoration designs will allow resource managers to improve cost-efficiencies in future restoration projects. [ABSTRACT FROM AUTHOR]

Oysters are notably susceptible to accumulating substantial amounts of cadmium (Cd), leading to food safety concerns, yet the molecular mechanisms are not fully understood. Previous study identified a significant correlation between polymorphisms in the Zip1 and Zip3 of Fujian oyster (Crassostrea angulata) and the levels of Cd accumulation. Zip1 and Zip3, belonging to the Zip family, are primarily responsible for the cellular transport of zinc and other metal ions. To delve deeper into their roles in Cd transport within oysters, this research cloned and analyzed the sequences of Fujian oyster Zip1 and Zip3. The open reading frames for Zip1 and Zip3 were 960 and 978 bp, respectively, encoding proteins of 319 and 325 amino acids. Following Cd exposure, the expression levels of these genes in the mantle, gills, and other tissues initially increased significantly before decreasing, demonstrating a dose-dependent response. The lowest expression levels were observed in the adductor muscle, with Zip1 reaching its highest expression in the mantle and Zip3 in the visceral mass. In vitro RNAi experiments revealed that silencing Zip1 led to a 1.26-fold decrease in new 113Cd accumulation in the mantle, whereas silencing Zip3 resulted in a 1.29-fold increase. Immunohistochemistry showed weak expression of Zip1 and Zip3 proteins in the connective tissue of the mantle. In summary, Zip1 and Zip3 in Fujian oyster can transport Cd as a substrate, and played different roles in the absorption and efflux of Cd. [ABSTRACT FROM AUTHOR]

Tetraploid oysters are of rising aquacultural importance because they can be used to produce 100% triploid seeds. Nevertheless, notable gaps in the understanding of the environmental preferences of tetraploid oyster larvae still exist. To investigate the combined effects of temperature and salinity on the growth, survival and metamorphosis of larvae of tetraploid Crassostrea gigas (GGGG), tetraploid C. angulata (AAAA) and two allotetraploid oysters (GGAG and AAGG), a total of 192 independent experiments were established, including 4 temperatures (21, 24, 27 and 30 ℃) × 4 salinities (22, 25, 28 and 31) × 4 populations (GGGG, AAAA, GGAG and AAGG) treatment combinations. Results showed that both temperature and salinity significantly affected growth, survival and metamorphosis of tetraploid oyster larvae and there was a significant interaction between salinity and temperature on survival and metamorphosis. The highest specific growth rate (SGR) of AAAA (7.61%), GGAG (8.47%) and AAGG (8.33%) occurred at a salinity-temperature combination of 25/27 °C, and that of GGGG (8.07%) occurred at a salinity-temperature combination of 25/24 °C. The highest accumulative survival rate (ASR) of AAAA (22.72%), GGAG (33.88%) and AAGG (31.10%) occurred at a salinity-temperature combination of 25/24 °C, and that of GGGG (27.51%) occurred at a salinity-temperature combination of 25/21 °C. The largest metamorphosis rate (MR) of AAAA (25.50%), GGAG (33.27%) and AAGG (32.73%) were found at a salinity-temperature combination of 28/27 °C, and that of GGGG (27.60%) were found at a salinity-temperature combination of 28/24 °C. In general, the larval performance of allotetraploid oysters was superior to that of autotetraploid oysters, with an allotetraploid superiority ranging from 3.57 to 9.39% in SGR, 32.82 to 103.26% in ASR and − 12.08 to 28.79% in MR. The optimum larval rearing salinity-temperature condition recommended for GGGG, GGAG and AAGG is 25–28 at 21–24 °C, while for AAAA is 25–28 at 24–27 °C; a temperature range of 24–27 °C and a salinity range of 28–31 are suggested to improve spat production of these four tetraploid oysters. [ABSTRACT FROM AUTHOR]

Introduction: Vibrio parahaemolyticus is a common pathogen that can cause seafood-borne gastroenteritis in humans. We determined the prevalence and characteristics of V. parahaemolyticus isolated from clinical specimens and oysters in Thailand. Methodology: Isolates of V. parahaemolyticus from clinical specimens (n = 77) and oysters (n = 224) were identified by biochemical testing, polymerase chain reaction (PCR) assays, and serotyping. The toxin genes, antimicrobial resistance, and β-lactamase production were determined. Results: A total of 301 isolates were confirmed as V. parahaemolyticus by PCR using specific primers for the toxR gene. The majority of clinical isolates carried the tdh+/trh− genotype (82.1%), and one of each isolate was tdh−/trh+ and tdh+/trh+ genotypes. One isolate from oyster contained the tdh gene and another had the trh gene. Twenty-six serotypes were characterized among these isolates, and O3:K6 was the most common (37.7%), followed by OUT:KUT, and O4:K9. In 2010, most clinical and oyster isolates were susceptible to antibiotics, with the exception of ampicillin. In 2012, clinical isolates were not susceptible to cephalothin (52.4%), streptomycin (95.2%), amikacin (66.6%), kanamycin (61.9%), and erythromycin (95.2%), significantly more frequently than in 2010. More than 95% of isolates that were not susceptible to ampicillin produced β-lactamase enzymes. Conclusions: We found toxin genes in two oyster isolates, and the clinical isolates that were initially determined to be resistant to several antibiotics. Toxin genes and antimicrobial susceptibility profiles of V. parahaemolyticus from seafood and environment should be continually monitored to determine the spread of toxin and antimicrobial resistance genes. [ABSTRACT FROM AUTHOR]

Predation is a dominant structuring force in ecological communities. In aquatic environments, predation on bivalves has long been an important focal interaction for ecological study because bivalves have central roles as ecosystem engineers, basal components of food webs, and commercial commodities. Studies of bivalves are common, not only because of bivalves' central roles, but also due to the relative ease of studying predatory effects on this taxonomic group. To understand patterns in the interactions of bivalves and their predators we synthesised data from 52 years of peer‐reviewed studies on bivalve predation. Using a systematic search, we compiled 1334 studies from 75 countries, comprising 61 bivalve families (N = 2259), dominated by Mytilidae (29% of bivalves), Veneridae (14%), Ostreidae (8%), Unionidae (7%), and Dreissenidae and Tellinidae (6% each). A total of 2036 predators were studied, with crustaceans the most studied predator group (34% of predators), followed by fishes (24%), molluscs (17%), echinoderms (10%) and birds (6%). The majority of studies (86%) were conducted in marine systems, in part driven by the high commercial value of marine bivalves. Studies in freshwater ecosystems were dominated by non‐native bivalves and non‐native predator species, which probably reflects the important role of biological invasions affecting freshwater biodiversity. In fact, while 81% of the studied marine bivalve species were native, only 50% of the freshwater species were native to the system. In terms of approach, most studies used predation trials, visual analysis of digested contents and exclusion experiments to assess the effects of predation. These studies reflect that many factors influence bivalve predation depending on the species studied, including (i) species traits (e.g. behaviour, morphology, defence mechanisms), (ii) other biotic interactions (e.g. presence of competitors, parasites or diseases), and (iii) environmental context (e.g. temperature, current velocity, beach exposure, habitat complexity). There is a lack of research on the effects of bivalve predation at the population and community and ecosystem levels (only 7% and 0.5% of studies respectively examined impacts at these levels). At the population level, the available studies demonstrate that predation can decrease bivalve density through consumption or the reduction of recruitment. At the community and ecosystem level, predation can trigger effects that cascade through trophic levels or effects that alter the ecological functions bivalves perform. Given the conservation and commercial importance of many bivalve species, studies of predation should be pursued in the context of global change, particularly climate change, acidification and biological invasions. [ABSTRACT FROM AUTHOR]

Oysters are rich nutrition sources that contain polysaccharides, proteins, peptides, phenolic compounds, minerals, and vitamins. In the search for compounds that exert anti-inflammatory effects in macrophages, we prepared hydrolyzed oyster (Magallana gigas) extracts (HOE) and evaluated their protective effects against inflammation and oxidative stress in RAW264.7 murine macrophages treated with lipopolysaccharide (LPS). As expected, LPS notably stimulated the generation of inflammatory molecules and associated regulatory proteins. However, HOE effectively blocked these effects in a concentration-dependent manner. This suppressive effect of HOE on inflammation appears to be responsible for blocking nuclear factor-κB (NF-κB) signaling. In addition, LPS-mediated reactive oxygen species generation RAW264.7 cells was highly inhibited by HOE treatment, which appears to be partially regulated by nuclear factor erythroid 2-related factor 2 (Nrf2). Moreover, HOE at high concentrations inhibited pro-inflammatory mediators and cytokines to a greater extent than BAY7085, a pharmacological NF-κB inhibitor, in LPS-treated RAW264.7 cells. Taken together, our results show that HOE effectively inhibits inflammation and oxidative stress via modulating the NF-κB and/or Nrf2 signaling in RAW264.7 macrophages and can be a potential therapeutic agent to prevent inflammation-related diseases. [ABSTRACT FROM AUTHOR]