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The Pacific oyster Crassostrea gigas lives in microbe-rich marine coastal systems subjected to rapid environmental changes. It harbours a diversified and fluctuating microbiota that cohabits with immune cells expressing a diversified immune gene repertoire. In the early stages of oyster development, just after fertilization, the microbiota plays a key role in educating the immune system. Exposure to a rich microbial environment at the larval stage leads to an increase in immune competence throughout the life of the oyster, conferring a better protection against pathogenic infections at later juvenile/adult stages. This beneficial effect, which is intergenerational, is associated with epigenetic remodelling. At juvenile stages, the educated immune system participates in the control of the homeostasis. In particular, the microbiota is fine-tuned by oyster antimicrobial peptides acting through specific and synergistic effects. However, this balance is fragile, as illustrated by the Pacific Oyster Mortality Syndrome, a disease causing mass mortalities in oysters worldwide. In this disease, the weakening of oyster immune defences by OsHV-1 µVar virus induces a dysbiosis leading to fatal sepsis. This review illustrates the continuous interaction between the highly diversified oyster immune system and its dynamic microbiota throughout its life, and the importance of this cross-talk for oyster health. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'. [ABSTRACT FROM AUTHOR]

Paralytic shellfish poisoning is an important concern for mollusk fisheries, aquaculture, and public health. In Galicia, NW Iberian Peninsula, such toxicity has been monitored for a long time using mouse bioassay. Therefore, little information exists about the precise toxin analogues and their possible transformations in diverse mollusk species and environments. After the change in the European PSP reference method, a refinement of the Lawrence method was developed, achieving a 75% reduction in chromatogram run time. Since the beginning of 2021, when this refinement Lawrence method was accredited under the norm UNE-EN ISO/IEC 17025, it has been used in the area to determine the toxin profiles and to estimate PSP toxicity in more than 4500 samples. In this study, we have summarized three years of monitoring results, including interspecific, seasonal, and geographical variability of PSP toxicity and toxin profile. PSP was detected in more than half of the samples analyzed (55%), but only 4.4% of the determinations were above the EU regulatory limit. GTX1,4 was the pair of STX analogs that produced the highest toxicities, but GTX2,3 was found in most samples, mainly due to the reduction of GTX1,4 but also by the higher sensitivity of the method for this pair of analogs. STX seems to be mainly a product of biotransformation from GTX2,3. The studied species (twelve bivalves and one gastropod) accumulated and transformed PSP toxins to a different extent, with most of them showing similar profiles except for Spisula solida and Haliotis tuberculata. Two seasonal peaks of toxicity were found: one in spring-early summer and another in autumn, with slightly different toxin profiles during outbreaks in relation to the toxicity during valleys. In general, both the total toxicity and toxin profiles of the southernmost locations were different from those in the northern part of the Atlantic coast and the Cantabrian Sea, but this general pattern is modified by the PSP history of some specific locations. [ABSTRACT FROM AUTHOR]

The glycoprotein-N-acetylgalactosamine β1,3-galactosyltransferase, known as T-synthase (EC 2.4.1.122), plays a crucial role in the synthesis of the T-antigen, which is the core 1 O-glycan structure. This enzyme transfers galactose from UDP-Gal to GalNAc-Ser/Thr. The T-antigen has significant functions in animal development, immune response, and recognition processes. Molluscs are a successful group of animals that inhabit various environments, such as freshwater, marine, and terrestrial habitats. They serve important roles in ecosystems as filter feeders and decomposers but can also be pests in agriculture and intermediate hosts for human and cattle parasites. The identification and characterization of novel carbohydrate active enzymes, such as T-synthase, can aid in the understanding of molluscan glycosylation abilities and their adaptation and survival abilities. Here, the T-synthase enzymes from the snail Pomacea canaliculata and the oyster Crassostrea gigas are identified, cloned, expressed, and characterized, with a focus on structural elucidation. The synthesized enzymes display core 1 β1,3-galactosyltransferase activity using pNP-α-GalNAc as substrate and exhibit similar biochemical parameters as previously characterised T-synthases from other species. While the enzyme from C. gigas shares the same structural parameters with the other enzymes characterised so far, the T-synthase from P. canaliculata lacks the consensus sequence CCSD, which was previously considered indispensable. [ABSTRACT FROM AUTHOR]

Molluscan aquaculture is often promoted as an alternative to wild shellfisheries, yet expansion of growing areas is sometimes opposed by groups concerned with aesthetics and use conflicts. Amidst these conflicts, public preferences remain unquantified in rigorous terms. This article presents a discrete choice experiment that elicits preferences for large-scale molluscan aquaculture with different production technologies and impacts. Results for a Connecticut (US) case study show that willingness to pay (WTP) is heterogeneous, with the largest effects on preferences due to localized water clarity impacts and employment gains. Preferences vary over alternative locations for growing areas but are positive on average, suggesting widespread public support. Results suggest that policies aiming to optimize WTP for molluscan aquaculture expansion should allow aquaculture attributes to vary over locations, consistent with public preferences. [ABSTRACT FROM AUTHOR]

Polyploidy has been suggested to negatively impact environmental stress tolerance, resulting in increased susceptibility to extreme climate events. In this study, we compared the genomic and physiological response of diploid (2n) and triploid (3n) Pacific oysters (Crassostrea gigas) to conditions present during an atmospheric heatwave that impacted the Pacific Northwestern region of the United States in the summer of 2021. Climate stressors were applied either singly (single stressor; elevated seawater temperature, 30°C) or in succession (multiple stressor; elevated seawater temperature followed by aerial emersion at 44°C), replicating conditions present within the intertidal over a tidal cycle during the event. Oyster mortality rate was elevated within stress treatments with respect to the control and was significantly higher in triploids than diploids following multiple stress exposure (36.4% vs. 14.8%). Triploids within the multiple stressor treatment exhibited signs of energetic limitation, including metabolic depression, a significant reduction in ctenidium Na+/K+ ATPase activity, and the dysregulated expression of genes associated with stress response, innate immunity, glucose metabolism, and mitochondrial function. Functional enrichment analysis of ploidy‐specific gene sets identified that biological processes associated with metabolism, stress tolerance, and immune function were overrepresented within triploids across stress treatments. Our results suggest that triploidy impacts the transcriptional regulation of key processes that underly the stress response of Pacific oysters, resulting in downstream shifts in physiological tolerance limits that may increase susceptibility to extreme climate events that present multiple environmental stressors. The impact of chromosome set manipulation on the climate resilience of marine organisms has important implications for domestic food security within future climate scenarios, especially as triploidy induction becomes an increasingly popular tool to elicit reproductive control across a wide range of species used within marine aquaculture. [ABSTRACT FROM AUTHOR]

Vibrio aestuarianus is a bacterium related to mass mortality outbreaks of the Pacific oyster, Crassostrea gigas in Europe. In this study, the role of different planktonic substrates (phytoplankton cells, marine aggregates and chitin fragments) in mediating V. aestuarianus 02/041 infection of oysters was evaluated by controlled infection experiments. It was shown that phytoplankton cells and, to a greater extent, marine aggregates, significantly promote V. aestuarianus 02/041 intake by C. gigas maintained under stressful conditions in the laboratory. Such intake is associated with higher concentration of the pathogen in the bivalve hemolymph and compromised health status of infected oysters. In contrast, chitin particles do not play a significant role as transmission vector for V. aestuarianus 02/041 infecting its bivalve host. Interestingly, incorporation into marine aggregates foster extracellular proteases (ECPs) activity and a higher expression of bacterial virulence genes, that are potentially involved in bivalve infection. Results from this study contribute to elucidate transmission patterns of V. aestuarianus 02/041 to C. gigas that may be useful for the development of efficient measures to prevent and control oyster disease outbreaks. [ABSTRACT FROM AUTHOR]

Crustaceans, which are highly susceptible to the effects of climate change, are critical for food security worldwide. Yet, management rarely evaluates the performance of alternative regulatory strategies under climate‐driven life history change. This limits the development of climate‐ready management plans, undermining fisheries sustainability. We compared the performance of alternative minimum legal size (MLS) regulations under shifts in growth and maturity for American lobster in the Gulf of Maine, the most valuable single‐species commercial fishery in the United States. Across the life history change scenarios examined, increasing MLS improved status indicators, while decreasing MLS eroded status indicators for spawning stock biomass, legal abundance, landings, and exploitation rate. Our results demonstrate that protecting the lobster stock by increasing MLS improves fishery output, highlighting that conservation and industry goals can be complementary. This study exemplifies the utility of MLS as a conservation measure for crustacean fisheries under climate change. [ABSTRACT FROM AUTHOR]

For the purpose of assessing human health exposure, it is necessary to characterize the toxins present in a given area and their potential impact on commercial species. The goal of this research study was: (1) to screen the prevalence and concentrations of lipophilic toxins in nine groups of marine invertebrates in the northwest Iberian Peninsula; (2) to evaluate the validity of wild mussels (Mytilus galloprovincialis) as sentinel organisms for the toxicity in non-bivalve invertebrates from the same area. The screening of multiple lipophilic toxins in 1150 samples has allowed reporting for the first time the presence of 13-desmethyl spirolide C, pinnatoxin G, okadaic acid, and dinophysistoxins 2 in a variety of non-traditional vectors. In general, these two emerging toxins showed the highest prevalence (12.5–75%) in most of the groups studied. Maximum levels for 13-desmethyl spirolide C and pinnatoxin G were found in the bivalves Magallana gigas (21 µg kg−1) and Tellina donacina (63 µg kg−1), respectively. However, mean concentrations for the bivalve group were shallow (2–6 µg kg−1). Okadaic acid and dinophysistoxin 2 with lower prevalence (1.6–44.4%) showed, on the contrary, very high concentration values in specific species of crustaceans and polychaetes (334 and 235 µg kg−−1, respectively), to which special attention should be paid. Statistical data analyses showed that mussels could be considered good biological indicators for the toxicities of certain groups in a particular area, with correlations between 0.710 (for echinoderms) and 0.838 (for crustaceans). Polychaetes could be an exception, but further extensive surveys would be needed to draw definitive conclusions. [ABSTRACT FROM AUTHOR]

Background: Host genetics influences the development of infectious diseases in many agricultural animal species. Identifying genes associated with disease development has the potential to make selective breeding for disease tolerance more likely to succeed through the selection of different genes in diverse signaling pathways. In this study, four families of Pacific oysters (Crassostrea gigas) were identified to be segregating for a quantitative trait locus (QTL) on chromosome 8. This QTL was previously found to be associated with basal antiviral gene expression and survival to ostreid herpesvirus 1 (OsHV-1) mortality events in Tomales Bay, California. Individuals from these four families were phenotyped and genotyped in an attempt to find candidate genes associated with the QTL on chromosome 8. Results: Genome-wide allele frequencies of oysters from each family prior to being planting in Tomales Bay were compared with the allele frequencies of oysters from respective families that survived an OsHV-1 mortality event. Six significant unique QTL were identified in two families in these genome-wide allele frequency studies, all of which were located on chromosome 8. Three QTL were assigned to candidate genes (ABCA1, PIK3R1, and WBP2) that have been previously associated with antiviral innate immunity in vertebrates. Conclusion: The identification of vertebrate antiviral innate immunity genes as candidate genes involved in molluscan antiviral innate immunity reinforces the similarities between the innate immune systems of these two groups. Causal variant identification in these candidate genes will enable future functional studies of these genes in an effort to better understand their antiviral modes of action. [ABSTRACT FROM AUTHOR]

Summer mortality of Crassostrea gigas occurs in Brazilian crops, with predominance in the final phase of cultivation, when they reach the commercial size, generating significant losses for local producers. In order to mitigate this problem, a technical solution, whose principle is based on long-term confinement at low temperatures (10 −12°C) for inducing a similar basal metabolism regime, has been developed. According to the current literature, if the spawning process is not triggered, a substantial reduction in the mortality rate can be achieved. This work evaluates not only the effectiveness of this technological solution to reduce summer mortality but also the quality associated to commercial attributes of the oysters as a final product. A ninety-one day experiment has been carried out and has shown that the proposed solution is able to maintain Crassostrea gigas diploid oysters alive and healthy. [ABSTRACT FROM AUTHOR]

This work investigates the application of Computer Vision to the problem of the automated counting and measuring of crabs and lobsters onboard fishing boats. The aim is to provide catch count and measurement data for these key commercial crustacean species. This can provide vital input data for stock assessment models, to enable the sustainable management of these species. The hardware system is required to be low-cost, have low-power usage, be waterproof, available (given current chip shortages), and able to avoid over-heating. The selected hardware is based on a Raspberry Pi 3A+ contained in a custom waterproof housing. This hardware places challenging limitations on the options for processing the incoming video, with many popular deep learning frameworks (even light-weight versions) unable to load or run given the limited computational resources. The problem can be broken into several steps: (1) Identifying the portions of the video that contain each individual animal; (2) Selecting a set of representative frames for each animal, e.g, lobsters must be viewed from the top and underside; (3) Detecting the animal within the frame so that the image can be cropped to the region of interest; (4) Detecting keypoints on each animal; and (5) Inferring measurements from the keypoint data. In this work, we develop a pipeline that addresses these steps, including a key novel solution to frame selection in video streams that uses classification, temporal segmentation, smoothing techniques and frame quality estimation. The developed pipeline is able to operate on the target low-power hardware and the experiments show that, given sufficient training data, reasonable performance is achieved. [ABSTRACT FROM AUTHOR]

Pacific oyster mortality syndrome (POMS), which is caused by Ostreid herpesvirus 1 (OsHV-1), causes economic losses in Pacific oyster (Crassostrea gigas) aquaculture in many countries. Reducing the mortality in disease outbreaks requires changing the host, pathogen and environment interactions to favor the host. Survivors of natural exposure to OsHV-1 are able to survive subsequent outbreaks. This has been replicated under laboratory conditions, suggesting the existence of an immune response. The aim of the present study is to compare the effects of prior exposure to infectious OsHV-1, heat-inactivated OsHV-1 and the chemical anti-viral immune stimulant poly I:C on mortality following exposure to virulent OsHV-1. All treatments were administered by intramuscular injection. Oysters were maintained at 18 °C for 14 days; then, the temperature was increased to 22 °C and the oysters were challenged with virulent OsHV-1. Heat-inactivated OsHV-1, infectious OsHV-1 and poly I:C all induced significant protection against mortality, with the hazard of death being 0.41, 0.18 and 0.02, respectively, compared to the controls, which had no immune priming. The replication of OsHV-1 on first exposure was not required to induce a protective response. While the underlying mechanisms for protection remain to be elucidated, conditioning for resistance to POMS by prior exposure to inactivated or infectious OsHV-1 may have practical applications in oyster farming but requires further development to optimize the dose and delivery mechanism and evaluate the duration of protection. [ABSTRACT FROM AUTHOR]

Since their introduction to North America in the 1980s, research to develop effective control tools for invasive mussels (Dreissena polymorpha and D. rostriformis bugensis) has been ongoing across various research institutions using a range of testing methods. Inconsistencies in experimental methods and reporting present challenges for comparing data, repeating experiments, and applying results. The Invasive Mussel Collaborative established the Toxicity Testing Work Group (TTWG) in 2019 to identify "best practices" and guide development of a standard framework for dreissenid mussel toxicity testing protocols. We reviewed the literature related to laboratory‐based dreissenid mussel toxicity tests and determined the degree to which standard guidelines have been used and their applicability to dreissenid mussel testing. We extracted detailed methodology from 99 studies from the peer‐reviewed and gray literature and conducted a separate analysis for studies using presettlement and postsettlement mussels. We identified specific components of methods and approaches that could be refined or standardized for dreissenid mussels. These components included species identification, collection methods, size/age class distinction, maintenance practices, testing criteria, sample size, response measures, reporting parameters, exposure methods, and mortality criteria. We consulted experts in the field of aquatic toxicology and dreissenid mussel biology on our proposed. The final recommendations contained in the present review are based on published standard guidelines, methods reported in the published and gray literature, and the expertise of TTWG members and an external panel. In addition, our review identifies research needs for dreissenid mussel testing including improved methods for early–life stage testing, comparative data on life stages and between dreissenid mussel species, inclusion of a reference toxicant, and additional testing of nontarget species (i.e., other aquatic organisms). Environ Toxicol Chem 2023;42:1649–1666. © 2023 His Majesty the King in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Pacific oyster (Crassostrea gigas) aquaculture has been economically impacted in many countries by Pacific oyster mortality syndrome (POMS), a disease initiated by Ostreid herpesvirus 1. The objectives of this study were to determine whether naturally exposed, adult C. gigas could act as reservoirs for OsHV-1 and explain the recurrent seasonal outbreaks of POMS and to test whether or not they were resistant to OsHV-1. In a laboratory infection experiment using thermal shock, OsHV-1 replication was not reactivated within the tissues of such oysters and the virus was not transmitted to naïve cohabitating spat. The adult oysters were resistant to intramuscular injection with a lethal dose of OsHV-1 and had 118 times lower risk of mortality than naïve oysters. Considered together with the results of other studies in C. gigas, natural exposure or laboratory exposure to OsHV-1 may result in immunity during subsequent exposure events, either in the natural environment or the laboratory. While adult C. gigas can carry OsHV-1 infection for lengthy periods, reactivation of viral replication leading to mortality and transmission of the virus to naïve oysters may require specific conditions that were not present in the current experiment. Further investigation is required to evaluate the mechanisms responsible for resistance to disease in oysters previously exposed to OsHV-1, whether immunity can be exploited commercially to prevent POMS outbreaks and to determine the source of the virus for recurrent seasonal outbreaks. [ABSTRACT FROM AUTHOR]

Simple Summary: The red squat lobster Pleuroncodes monodon, a key crustacean in the Humboldt Current System (HCS), plays an important role as predator and prey of several species of commercial interest. Off the Chilean coast, P. monodon presents benthic habits and constitutes the main resource of the industrial crustacean fishery. In contrast, off the coast of Peru, the red squat lobster exhibits pelagic habits, with knowledge gaps on traits of its ecology and no commercial fishery activities. Therefore, this review explores research conducted in the HCS, including ecological aspects and its use as a marine bioresource. This study focused on gathering available information on Pleuroncodes monodon, a widely distributed crustacean in the Humboldt Current System. Off the Chilean coast, this species presents benthic habits and constitutes the main resource of the industrial crustacean fishery; many studies have been carried out on its life cycle during the last century. In contrast, off the coast of Peru, this species exhibits mainly pelagic habits, with latent information gaps on aspects of its life history and no commercial fishery activities, such as catching, taking or harvesting from the marine environment. P. monodon is an ecologically important species, as a source of energy for its predators, which include invertebrates, birds, marine mammals and fish of commercial interest. Thus, P. monodon seems to play a key role in this ecosystem, mainly as an intermediate link between top predators and the first links in the food chain. In addition, this species presents various adaptation strategies to the changing oceanographic parameters of the areas it inhabits, even tolerating hypoxic environments and great depths in order to avoid being predated. Likewise, from an economic viewpoint, it has a high commercial value as a marine bioresource with great potential in the pharmaceutical and food industries. Considering this, more studies must be carried out to corroborate the biological, ecological, and fishing importance of this species in order to generate efficient management measures and ensure a sustainable fishery. [ABSTRACT FROM AUTHOR]

Manas, H.M.; Ghosh, S.; Rohit, P.; Rajesh, K.M.; Abdussamad, E.M.; Satishkumar, M.; Pokkathappada, A.A.; Rathinam, M.M., and Divipala, I., 2023. Feeding aspects of dolphinfish, Coryphaena hippurus (Linnaeus, 1758), exploited from Indian waters. Journal of Coastal Research, 39(4), 675–684. Charlotte (North Carolina), ISSN 0749-0208. The common dolphinfish, Coryphaena hippurus, is one of the top predatory fish in pelagic waters, landed all along the Indian coast. The present study was conducted to gain a holistic knowledge of the food and feeding habits of the common dolphinfish from Indian waters. Around 2559 specimens were studied, of which 65.8% were male and 34.2% were female. The species fed on several prey items encountered in all months, scads being the dominant group and the highest preference in fishes >60 cm total length (TL). Fishes of TL <45 cm mainly fed on whitebaits; those 45–60 cm fed on crabs and scads, indicating a shift in prey preference with change in body size and the species being opportunistic feeders, preferring abundant prey species in the environment. August to March showed similar food preferences and overlapping of prey items. This study will help us understand the trophodynamics of the common dolphinfish, allowing policy makers to formulate unified management and conservation measures for sustainable exploitation of the species from Indian waters. [ABSTRACT FROM AUTHOR]

White‐nose syndrome is a fungal disease that is threatening bat populations across North America. The disease primarily affects cave‐hibernating bats by depleting fat reserves during hibernation and causing a range of other physiological consequences when immune responses are suppressed. Since it was first detected in 2006, the disease has killed millions of bats and is responsible for extensive local extinctions. To better understand the effects of white‐nose syndrome on various bat species, we analyzed summer acoustic survey data collected from 2016 to 2020 at nine US National Parks within the Great Lakes region. We examined the effect that white‐nose syndrome, time of the year relative to pup volancy, habitat type, and regional variation (i.e., park) have on the acoustic abundance (i.e., mean call abundance) of six bat species. As expected, little brown bat (Myotis lucifugus) and northern long‐eared bat (Myotis septentrionalis), both hibernating species, experienced a significant decline in acoustic abundance following white‐nose syndrome detection. We observed a significant increase in acoustic abundance as white‐nose syndrome progressed for hoary bats (Lasiurus cinereus) and silver‐haired bats (Lasionycteris noctivagans), both migratory species that are not impacted by the disease. Contrary to our predictions, we observed an increase in big brown bat (Eptesicus fuscus; hibernating) acoustic abundance and a decrease in eastern red bat (Lasiurus borealis; migratory) acoustic abundance following the detection of white‐nose syndrome. We did not observe any significant changes after the onset of white‐nose syndrome in the seasonal patterns of acoustic activity related to pup volancy, suggesting that production or recruitment of young may not be affected by the disease. Our results suggest that white‐nose syndrome is affecting the acoustic abundance of certain species; however, these changes may not be a result of reduced reproductive success caused by the disease. In addition, species population dynamics may be indirectly affected by white‐nose syndrome as a result of reduced competition or a foraging niche release. We also found that for parks located at higher latitudes, little brown bat and northern long‐eared bat were more likely to experience greater declines in acoustic abundance as a result of white‐nose syndrome. Our work provides insight into species‐specific responses to white‐nose syndrome at a regional scale and examines factors that may facilitate resistance or resiliency to the disease. [ABSTRACT FROM AUTHOR]

Species of the marine dinoflagellate genus Karenia are known to produce various potent biotoxins and can form noxious blooms that cause mass mortalities of fish and shellfish. To date, harmful blooms of the species K. mikimotoi have been reported in Korea, but K. papilionacea was recently recorded off the southern coast of Korea. Here, we developed a quantitative real-time PCR (qRT-PCR) assay with specific primer pairs for the accurate detection and quantification of these two similar-looking unarmored species, K. mikimotoi and K. papilionacea, and investigated their distribution and dynamics in Korean coastal waters. Overall, K. papilionacea had not only a wider distribution, but also higher cell abundances (15–2553 cells L−1) than K. mikimotoi (3–122 cells L−1) in surface waters. Of 18 sampling sites, the two Karenia species were found to coexist at two sites. During monitoring at a fixed station (S5), K. papilionacea was generally predominant over K. mikimotoi; however, the two species exhibited similar dynamics and occasionally co-occurred. Both Karenia species showed similar physiological responses to temperature and salinity, requiring similar conditions for optimum growth. These results suggest that blooms of the two species may co-occur and induce a synergistic adverse effect on marine environments. [ABSTRACT FROM AUTHOR]

Implementation of precautionary approach (PA) management systems has generally proven to be a betterment over historic management practices in sustainable use of fisheries resources. However, PA management systems can minimize the application of holistic assessment advice. Single-indicator approaches, typically featuring a measure of stock biomass or abundance, have emerged as dominant in developing methods for PA frameworks. This often leads to advice generated from these frameworks being applied within narrowly focused decision-making pathways and can minimize management application of important ancillary factors. We argue this outcome is counter to the intent of PA management systems and that multi-indicator PA frameworks are a better approach. In this analysis, we detail the multi-indicator PA system development for demonstrative case studies focused on three lucrative fisheries resources in Newfoundland & Labrador, highlighting how multi-indicator PAs are potentially a better approach for the management of stocks with a contrasting range of ecological roles, socioeconomic importance, and data quality. The work is intended to generate a discussion on how PA frameworks should evolve to best suit management purposes. [ABSTRACT FROM AUTHOR]

Simple Summary: Bivalve shellfish aquaculture represents a sustainable and nutritionally sound path to provide food for a growing global population. New advances in feed formulation, namely microencapsulation, demonstrated great potential to face key bivalve nutrition problems, enabling increased quality production as the lack of naturally occurring food may result in non-lethal prejudice with losses in organoleptic characteristics. To test the applicability of algae-based microencapsulation, this study evaluated the food intake in five bivalve species that are highly valuable and widely cultivated throughout the world: Pacific oyster, grooved razor shell, carpet shell clam, manila clam, and common cockle. Four microencapsulated diets were implemented, incorporating two different microalgae species into two different diameter pellets. Overall, all the tested diets were easily ingested by the bivalves, although species-related profiles of food intake depending on the pellet size were observed. These results enabled a better selection of feed with appropriate profiles, offering a margin of opportunity to improve bivalve nutritional value and contributing to reinforcing knowledge in the framework of shellfish aquaculture. Moreover, a combination of different microalgae could be explored in the future as it may provide good sources of essential nutrients and a better product for the final consumer. Bivalve mollusks represent a nutritious source with a low environmental impact; as a result, they are one of the most attractive aquaculture options. Advances in microencapsulation technology offer great potential to face key bivalve nutrition problems, and an alga-based microencapsulated diet can turn enriched bivalves into potential functional foods. The central goal of this study was the evaluation of food intake as a function of particle size and microalga content following the supply of four microencapsulated diets, incorporating as core material Nannochloropsis sp. or Tetraselmis sp. in 20 or 40 µm diameter pellets (diets N20, T20, N40, and T40, respectively) in five bivalve species (Magallana gigas, Solen marginatus, Ruditapes decussatus, Ruditapes philippinarum, and Cerastoderma edule). Overall, all tested diets were easily ingested, although food intake was higher for N20 (except for the S. marginatus, which showed a higher rate for the diet T40). Concerning a size-related analysis, C. edule and S. marginatus favored, respectively, smaller and bigger pellet-sized diets, with no signs of selectivity for microalga species. The diet T20 was the lesser ingested, except for C. edule. This knowledge enables a better selection of feed with appropriate and species-adjusted profiles, contributing to the optimization of microencapsulated diets for bivalve rearing and a better final product. [ABSTRACT FROM AUTHOR]

Dense single nucleotide polymorphism (SNP) arrays are essential tools for rapid high-throughput genotyping for many genetic analyses, including genomic selection and high-resolution population genomic assessments. We present a high-density (200 K) SNP array developed for the Eastern oyster (Crassostrea virginica), which is a species of significant aquaculture production and restoration efforts throughout its native range. SNP discovery was performed using low-coverage whole-genome sequencing of 435 F1 oysters from families from 11 founder populations in New Brunswick, Canada. An Affymetrix Axiom Custom array was created with 219,447 SNPs meeting stringent selection criteria and validated by genotyping more than 4,000 oysters across 2 generations. In total, 144,570 SNPs had a call rate >90%, most of which (96%) were polymorphic and were distributed across the Eastern oyster reference genome, with similar levels of genetic diversity observed in both generations. Linkage disequilibrium was low (maximum r² ~0.32) and decayed moderately with increasing distance between SNP pairs. Taking advantage of our intergenerational data set, we quantified Mendelian inheritance errors to validate SNP selection. Although most of SNPs exhibited low Mendelian inheritance error rates overall, with 72% of called SNPs having an error rate of <1%, many loci had elevated Mendelian inheritance error rates, potentially indicating the presence of null alleles. This SNP panel provides a necessary tool to enable routine application of genomic approaches, including genomic selection, in C. virginica selective breeding programs. As demand for production increases, this resource will be essential for accelerating production and sustaining the Canadian oyster aquaculture industry. [ABSTRACT FROM AUTHOR]

Crassostrea gigas oysters represent a significant global food source with 4.7 million tons harvested per year. In 2001, the bacterium Vibrio aestuarianus subsp. francensis emerged as a pathogen that causes adult oyster mortality in France and Ireland. Its impact on oyster aquaculture has increased in Europe since its re‐emergence in 2012. To better understand the evolutionary mechanisms leading to the emergence and persistence over time of this pathogen, we conducted a survey of mollusc diseases through national reference laboratories across Europe. We analysed 54 new genomes of Vibrio aestuarianus (Va) isolated from multiple environmental compartments since 2001, in areas with and without bivalve mortalities. We used a combination of comparative genomics and population genetics approaches and show that Va has a classical epidemic population structure from which the pathogenic Va francensis subspecies emerged and clonally expanded. Furthermore, we identified a specific cus‐cop‐containing island conferring copper resistance to Va francensis whose acquisition may have favoured the emergence of pathogenic lineages adapted and specialized to oysters. [ABSTRACT FROM AUTHOR]

Simple Summary: The history of oyster culture consists of a succession of developmental phases using different species, followed by collapses associated with infectious diseases. The Pacific oyster (Crassostrea gigas), native to the northwest Pacific Ocean, was characterized by wide adaptability, and translocated to support major aquaculture industries in many countries around the world. A deadly herpesvirus, Ostreid herpesvirus-1 (OsHV-1), has hit the superior oyster since 1991. OsHV-1 infection, combined with subsequent bacteraemia by opportunistic bacteria, has brought heavy losses to the main production regions of the Pacific oyster. Because of the considerable economic importance of Pacific oysters, there is a wealth of information available on diseases that affect them around the world. Little comprehensive information is available about the epidemiology status of major disease-causing agents in China. On the other hand, the scale and yields of Pacific oyster increased rapidly in recent years, as a result of the introduction and popularization of triploid oysters. In the present study, a comprehensive survey of potential pathogens associated with mortality events of Pacific oysters was carried out. Our results highlight the potential risks of OsHV-1, Vibrio natriegens, and Vibrio alginolyticus to the aquaculture industry of the Pacific oyster in China. The Pacific oyster (Crassostrea gigas) aquaculture industry increased rapidly in China with the introduction and promotion of triploid oysters in recent years. Mass mortalities affecting different life stages of Pacific oysters emerged periodically in several important production areas of Northern China. During 2020 and 2021, we conducted a passive two-year investigation of infectious pathogens linked to mass mortality. Ostreid herpesvirus-1 (OsHV-1) was detected to be associated with mass mortalities of hatchery larvae, but not juveniles and adults in the open sea. Protozoan parasites, such as Marteilia spp., Perkinsus spp. and Bonamia spp. were not detected. Bacterial isolation and identification revealed that Vibrio natriegens and Vibrio alginolyticus were the most frequently (9 out of 13) identified two dominant bacteria associated with mass mortalities. Pseudoalteromonas spp. was identified as the dominant bacteria in three mortality events that occurred during the cold season. Further bacteriological analysis was conducted on two representative isolates of V. natriegens and V. alginolyticus, designated as CgA1-1 and CgA1-2. Multisequence analysis (MLSA) showed that CgA1-1 and CgA1-2 were closely related to each other and nested within the Harveyi clade. Bacteriological investigation revealed faster growth, and more remarkable haemolytic activity and siderophore production capacity at 25 °C than at 15 °C for both CgA1-1 and CgA1-2. The accumulative mortalities of experimental immersion infections were also higher at 25 °C (90% and 63.33%) than at 15 °C (43.33% and 33.33%) using both CgA1-1 and CgA1-2, respectively. Similar clinical and pathological features were identified in samples collected during both naturally and experimentally occurring mortalities, such as thin visceral mass, discolouration, and connective tissue and digestive tube lesions. The results presented here highlight the potential risk of OsHV-1 to hatchery production of larvae, and the pathogenic role of V. natriegens and V. alginolyticus during mass mortalities of all life stages of Pacific oysters in Northern China. [ABSTRACT FROM AUTHOR]

Simple Summary: Invasive tunicates have become a global threat to shellfish aquaculture sites in recent decades, particularly mussel farms. In our study, the effectiveness of five eradication treatments (air exposure, freshwater immersion, sodium hypochlorite, hypersaline solution and acetic acid) was tested for the solitary tunicate Styela plicata. The effects on blue mussel Mytilus edulis survival and growth were also evaluated. The acetic acid treatment was the most effective in eliminating tunicates, although further studies are needed to achieve total survival in mussels. We suggest that the treatments are also likely to produce more effective results as prophylactic measures, applied in controlled environment in mussel seed. In 2017, aquaculture producers of the Albufeira lagoon, Portugal, reported an invasion of tunicates that was disrupting mussel production, particularly the tunicate Styela plicata (Lesueur, 1823). A totally effective eradication method still does not exist, particularly for S. plicata, and the effects of the eradication treatments on bivalves' performance are also poorly understood. Our study examined the effectiveness of eradication treatments using three laboratory trials and five treatments (air exposure, freshwater immersion, sodium hypochlorite, hypersaline solution and acetic acid) for S. plicata, as well as their effects on survival and growth of blue mussel Mytilus edulis Linnaeus, 1758. While air exposure and freshwater immersion caused a 27% mortality rate in S. plicata, the acetic acid treatment was the most effective in eliminating this species (>90% mortality). However, a 33–40% mortality rate was registered in mussels. Both species were not affected by the hypersaline treatment in the last trial, but the sodium hypochlorite treatment led to a 57% mortality rate in mussels. Differences in mussels' growth rates were not detected. These trials represent a step forward in responding to the needs of aquaculture producers. However, further studies are needed to investigate the susceptibility of tunicates to treatments according to sexual maturation, as well as to ensure minimum mussel mortality in the most effective treatments, and to better understand the effects on mussel physiological performance in the long-term. [ABSTRACT FROM AUTHOR]

Blue mussels from the genus Mytilus are an abundant component of the benthic community, found in the high latitude habitats. These foundation species are relevant to the aquaculture industry, with over 2 million tonnes produced globally each year. Mussels withstand a wide range of environmental conditions and species from the Mytilus edulis complex readily hybridize in regions where their distributions overlap. Significant effort has been made to investigate the consequences of environmental stress on mussel physiology, reproductive isolation, and local adaptation. Yet our understanding on the genomic mechanisms underlying such processes remains limited. In this study, we developed a multi species medium‐density 60 K SNP‐array including four species of the Mytilus genus. SNPs included in the platform were called from 138 mussels from 23 globally distributed mussel populations, sequenced using a whole‐genome low coverage approach. The array contains polymorphic SNPs which capture the genetic diversity present in mussel populations thriving across a gradient of environmental conditions (~59 K SNPs) and a set of published and validated SNPs informative for species identification and for diagnosis of transmissible cancer (610 SNPs). The array will allow the consistent genotyping of individuals, facilitating the investigation of ecological and evolutionary processes in these taxa. The applications of this array extend to shellfish aquaculture, contributing to the optimization of this industry via genomic selection of blue mussels, parentage assignment, inbreeding assessment and traceability. Further applications such as genome wide association studies (GWAS) for key production traits and those related to environmental resilience are especially relevant to safeguard aquaculture production under climate change. [ABSTRACT FROM AUTHOR]

The freshwater Indian apple snail, Pila globosa (Swainson, 1822), is well adapted to the equatorial and tropical regions of the planet, where there are periods of heavy rain that are followed by dry spells. It is the most important biotic component of the ecosystem and a dominating member of its communities, making it crucial for the health of the ecosystem. It has a significant economic importance in the international trade market. The flesh of P. globosa is used in aquaculture and as a human protein supplement because of its high protein and low fat content, along with essential fatty acids. The shell of P. globosa is a good source of minerals, especially calcium. P. globosa has been employed in traditional medicinal practices to treat diseases like high blood pressure, heart disease, asthma, rickets, rheumatoid arthritis, osteoporosis, calcium metabolism, bleeding piles, constipation, diarrhoea, smallpox, syphilis, dizziness, anxiety, nervousness, urticaria, night blindness, and conjunctivitis. It is also used to regulate body temperature, to speed up wound healing, to treat circulatory issues, to revive virility and vitality, to treat weakness, and for vision improvement. P. globosa has antimicrobial, antiinflammatory, anti-oxidative, anti-cancer, and immune boosting properties, and it can be a benefit to mankind. This review provides an overview of the ecological and economic importance, nutritional and ethno-medicinal values of the snail P. globosa. [ABSTRACT FROM AUTHOR]

Herein, moribund mud crab (Scylla serrata) samples were collected from various farming systems, brooders from wild and hatchery quarantine section, located in Tamil Nadu, Andhra Pradesh, and Odisha. The infected crabs showed clinical signs of lethargic movement with the sleeping position in the culture ponds, tanks, and wild-caught. In the wet mount study, massive numbers of viral giant cells were observed in the infected crab hepatopancreas and connective tissue. Mud crab reovirus (MCRV) inclusion bodies were noticed in the connective tissue of hepatopancreas, gill lamellae, muscle and gonads in histopathology analysis. Also, viral particles proliferated into the cytoplasm of the cells, but they did not affect the host nuclei. The infected crab samples were confirmed in the PCR using specific primers (ReoF and ReoR) and rDNA sequence analysis showed 99% similarity with mud crab reovirus and Scylla serrata reovirus (OL466868 and OL466869). The ultrastructural study (TEM) revealed that MCRV viral particles ranged between 70 and 75 nm in diameter, icosahedral shape, and non-enveloped with two capsid layers located in the cytoplasm of the cells. The prevalence of mud crab reovirus infection was recorded between 80 and 100% in cultured farms within 25 days and 19–33% in the wild from the collected samples. In the pathogenicity study, intramuscular injection bioassay reached 100% mortality and a co-habitation assay was 70% mortality on 14 days of MCRV post-infection. Thus, our results suggest that MCRV is highly pathogenic to mud crab culture. [ABSTRACT FROM AUTHOR]

To estimate the quality of mussels during storage, the mortality, succinate dehydrogenase (SDH) activity, extractive components, viable bacterial count (VBC), and bacterial flora of live mussels were investigated. The hierarchical cluster analysis, based on extractive components and VBC, taste active value (TAV), and equivalent umami concentration (EUC), suggested that metabolite composition, bacterial, and taste changing patterns of samples stored at 5 and 10°C differed from those stored at 0°C. The mortality of mussels stored at 5 and 10°C was lower than those at 0°C. The gills of live mussels stored at 0°C for more than 7 days exhibited significantly lower SDH activity than those stored at 5 and 10°C. There was no significant difference in EUC among the samples stored at different temperatures, but a significantly higher TAV of Ala and succinic acid was observed in live mussels after 12 days of storage at 5 and 10°C than in those stored at 0°C. Next‐generation sequencing analysis showed that samples stored at 5 and 10°C lost bacterial diversity, and their bacterial flora changed compared to that before storage. Considering these results, the most suitable storage condition to maintain high quality for live mussels is 5°C for less than 7 days. [ABSTRACT FROM AUTHOR]

Due to the increasing mass mortality of Pinna nobilis, mainly caused by the protozoan Haplosporidium pinnae along the Mediterranean Sea, it is necessary to develop rapid and effective methods to detect the pathogen. The present study describes the development and validation of a species-specific assay based on hydrolysis probe chemistry to detect H. pinnae DNA from faeces and pseudofaeces of P. nobilis. During a study campaign in the Gulf of Trieste (Italy) in the spring and summer of 2022, 18 samples (10 faeces and 8 pseudofaeces) were collected. DNA was isolated from all samples and the presence of H. pinnae was tested by amplifying a small portion of 18S rDNA using qPCR. The newly developed assay detected positive H. pinnae in the faeces of the fan mussel in the spring, while no evidence of an outbreak of H. pinnae was found in the summer. In addition, the method proved to be noninvasive and can be used to monitor suspected H. pinnae infections in the early stages when bivalves are still vital. Furthermore, fecal analysis allows the monitoring of P. nobilis without dissecting tissues. The presented assay can also be used to routinely monitor the progress of mass mortalities caused by H. pinnae and to screen for the pathogen in live fan mussels and other environmental matrices, such as water, sediment, and faeces from other species that can host the protozoan. [ABSTRACT FROM AUTHOR]

Background. The diarrhoeal shellfish poisoning (DSP) toxin is a powerful marine biological toxin. Eating DSP toxin-contaminated mussels will lead to serious gastrointestinal diseases. To this end, a method for the detection of DSP toxins using near-infrared reflectance spectroscopy combined with pattern recognition is proposed. Material and methods. In the range from 950−1700 nm, spectral data of healthy mussels and DSP-contaminated mussels were obtained. To select the optimal band subsets, a band selection algorithm based on model cluster analysis was applied. As distinguishing DSP toxin-contaminated mussels from healthy mussels is a classification problem of imbalanced data, an improved fuzzy support vector machine-based recognition method was proposed. The influence of the parameters of the band selection algorithm and the fuzzy support vector machine on the model performance was analyzed. Results. Compared with the traditional support vector machine, the proposed model has better performance in detecting DSP toxins and is not affected by the imbalance ratio. Its geometric mean value can reach 0.9886 and the detection accuracy can reach 98.83%. Conclusion. The results show that as an innovative, fast and convenient analytical method, near-infrared spectroscopy is feasible for the detection of DSP toxins in mussels. [ABSTRACT FROM AUTHOR]

Recent IUCN assessments had resulted in up listing of the status of butterfly rays due to concerns of overfishing, but inadequate biological understanding of these rays prevents meaningful conservation and management measures. Therefore, this study was undertaken to address knowledge gaps in the reproductive biology and diet of longtail butterfly ray (Gymnura poecilura) and zone tail butterfly ray (Gymnura zonura) in Malaysian waters. From surveys of landing sites and fish markets from years 2017 to 2022, size (disc width, DW), weight and maturity were recorded, and stomachs were collected from 94 G. poecilura (N = 39 females and 55 males) and 20 G. zonura (N = 10 females and 10 males) specimens. The length‐weight relationships were significantly different between sexes for G. poecilura. The size at maturity (DW50) was estimated to be 476.0 mm (females), 385.0 mm (males) for G. poecilura and 442.0 mm (combined) for G. zonura. The number of embryos ranged from 1 to 6, and the embryo size was between 73.90 to 130.44 mm DW. Dietary analysis of stomach contents revealed that fish prey was dominant in both G. poecilura [94.4% Index of Relative Importance (IRI)] and G. zonura (100% IRI). Ontogenetic shift was seen in G. poecilura that fed on more variety of prey items, including shrimps, squids and crabs with an increase in body size. Both species co‐occur all along coastal Malaysia although G. zonura is rarely encountered from fisheries surveys along the Strait of Malacca. Given similar habitat associations and dietary habits, G. poecilura may be able to outcompete G. zonura across their shared habitat range. The validity of G. japonica and G. micrura records in Malaysia remains questionable and requires future investigation. [ABSTRACT FROM AUTHOR]

Mass mortalities caused by Ostreid herpesvirus 1 (OsHV-1) has led to changes in the global approach to Pacific oyster (Crassostrea gigas) breeding and farm management. After entering a waterway OsHV-1 can become endemic, resulting in seasonally recurrent outbreaks of disease. To prevent spread of OsHV-1, biosecurity measures need to consider the host range of the virus in terms of susceptibility or the ability to sequester and translocate (i.e., carry) infectious virus. Using a targeted field survey and pilot laboratory cohabitation challenge, the present study focused on the potential for OsHV-1 transmission via biofouling organisms common to vessels and aquaculture infrastructure. In the field study, an OsHV-1 disease event did not result in concurrent virus detections in co-located ascidians, barnacles, or Sydney rock oysters. The pilot laboratory challenge involved exposure of diverse biofouling assemblages to high OsHV-1 infection pressure by using injected Donor Pacific oysters to control the dose and exposure time. While transmission of OsHV-1 from exposed biofouling assemblages to naïve Pacific oysters was not observed, there was a high prevalence of detectable OsHV-1 DNA in bryozoan species (83.3 to 100 %) that persisted 6 days after removing the source. Evaluation of the sample preparation and qPCR methodology for detection of OsHV-1 DNA in non-oyster biofouling species indicates that caution is required when assessing qPCR results as some sample matrices showed significant reductions in analytical sensitivity (e.g., Bugula neritina, Didemnum sp., and mixed organisms associated with marine surface sediments). This study advances our knowledge regarding the host range of OsHV-1 and improves our understanding of the likelihood of OsHV-1 translocation via biofouling of vessels and aquaculture equipment. This knowledge can inform specific disease control and biosecurity protocols. [ABSTRACT FROM AUTHOR]

Human norovirus (HuNoV) is the leading foodborne pathogen causing nonbacterial gastroenteritis worldwide. The oyster is an important vehicle for HuNoV transmission, especially the GI.1 HuNoV. In our previous study, oyster heat shock protein 70 (oHSP 70) was identified as the first proteinaceous ligand of GII.4 HuNoV in Pacific oysters besides the commonly accepted carbohydrate ligands, a histo-blood group antigens (HBGAs)-like substance. However the mismatch of the distribution pattern between discovered ligands and GI.1 HuNoV suggests that other ligands may exist. In our study, proteinaceous ligands for the specific binding of GI.1 HuNoV were mined from oyster tissues using a bacterial cell surface display system. Fifty-five candidate ligands were identified and selected through mass spectrometry identification and bioinformatics analysis. Among them, the oyster tumor necrosis factor (oTNF) and oyster intraflagellar transport protein (oIFT) showed strong binding abilities with the P protein of GI.1 HuNoV. In addition, the highest mRNA level of these two proteins was found in the digestive glands, which is consistent with GI.1 HuNoV distribution. Overall the findings suggested that oTNF and oIFT may play important roles in the bioaccumulation of GI.1 HuNoV. [ABSTRACT FROM AUTHOR]

This study summarises six years of spatio-temporal patterns of the discarded demersal community fauna recorded by onboard scientific observer program for both artisanal and industrial crustacean fisheries between 2014 and 2019, from mesophotic to aphotic depths (96 to 650 m) along the southern Humboldt Current System (28–38°S). In this period, one cold and two warm climatic events were observed during the austral summer 2014, 2015–2016 (ENSO Godzilla), and 2016–2017 (coastal ENSO), respectively. Satellite information showed that Chlorophyll-a concentration varied seasonally and latitudinally, associated with upwelling centres, while equatorial wind stress decreased southward of 36°S. Discards were composed of 108 species, dominated by finfish and molluscs. The Chilean hake Merluccius gayi was dominant and ubiquitous (occurrence, 95% of 9104 hauls), being the most vulnerable species of the bycatch. Three assemblages were identified: assemblage 1 (~200 m deep), dominated by flounders Hippoglossina macrops and lemon crabs Platymera gaudichaudii, assemblage 2 (~260 m deep), dominated by squat lobsters Pleuroncodes monodon and Cervimunida johni and assemblage 3 (~320 m depth), dominated by grenadiers Coelorinchus aconcagua and cardinalfish Epigonus crassicaudus. These assemblages were segregated by depth, and varied by year, and geographic zone. The latter represented changes in the width of the continental shelf, increasing southward of 36°S. Alpha-diversity indexes (richness, Shannon, Simpson, and Pielou) also varied with depth and latitude, with higher diversity in deeper continental waters (>300 m), between 2018–2019. Finally, at a spatial scale of tens of kilometres, and a monthly basis, interannual variations of biodiversity occurred in the demersal community. Surface sea temperature, chlorophyll-a, or wind stress did not correlate with discarded demersal fauna diversity of the crustacean fishery operating along central Chile. [ABSTRACT FROM AUTHOR]

The nursery culture of bivalves typically relies on the feeding of costly live microalgae, while the use of natural sources of phytoplankton for feed is uncertain due to their variable quality and abundance. Replacement diets have been applied in bivalve nursery culture to replace live microalgae with varying success. This study investigated the potential use of two concentrated microalgal diets at a range of levels of substitution with live microalgae. Shellfish Diet 1800® (called SD) and LPB™ Frozen Shellfish Diet® (called LPB) were fed to juvenile green-lipped mussels (Perna canaliculus) at five levels of substitution for live microalgae (i.e., 0, 25, 50, 75, and 100%) for 27 days. The mortality of mussels fed with 100% LPB replacement was significantly higher than the mortality of mussels fed at the lower levels of replacement, i.e., 0 and 25%. The overall final size of spat tended to decrease with the increasing level replacement of live microalgae. Proximate analysis (i.e., crude ash-free dry weight, crude protein, crude lipid, and carbohydrate) showed that only the proportion of carbohydrate content of spat was influenced by feeding treatments, with the mean total carbohydrate content of mussels tending to decrease with increasing levels of replacement of live microalgae. The results indicate that both concentrated microalgal feeds (SD and LPB) are effective at replacing live microalgae by up to 50% without compromising the survival and nutritional profile (AFDW, protein, lipid, and carbohydrate content) of juvenile green-lipped mussels and are therefore a useful resource for improving the efficiency of production. [ABSTRACT FROM AUTHOR]

Sound is an effective channel for the transfer of information underwater. While it is known that fish and whales can use sound for communication, and as a cue to localise predators and prey, much less is known about sound production in invertebrates. Here we describe sounds produced by two of the most common marine crustacean zooplankton in the Northern hemisphere: Northern krill (Meganyctiphanes norvegica) and copepods (Calanus spp.). The recorded sounds were taxon-specific and within the hearing range of common planktivorous fish. We recorded similar sounds in the laboratory and in the field. In krill, the sound co-occurred with a tail flip, and the amplitude of the sound was correlated to the displacement distance of the animal, indicating a potential sound producing mechanism. Our findings highlight the possibility that zooplankton sounds could be used as a cue for their predators and for intraspecific communication. [ABSTRACT FROM AUTHOR]

In estuarine systems, salinity changes by freshwater inflows and tides affect the survival and behaviour of euryhaline species. Juvenile Chinese mitten crabs, Eriocheir sinensis , are considered to live in fresh water during their complex life history, whilst some are found in coastal wetlands. To understand how juveniles disperse in estuarine residence, we investigated their survival, feed intake and salinity preference after acclimating in three different water situations (i.e., fresh water, salt water and alternation between fresh water and salt water). We supposed that behavioural alternation and salinity preference would play an essential role in their acclimation. Results showed no significant difference in survival and feed intake amongst the three groups of juveniles (P > 0.05) in acclimation trials. However, the feed intake of crabs in each group was declining after changing water every three days. In the salinity preference experiment, crabs from fresh water preferred 0 ‰ and 12 ‰ , whereas those from salinity and alternation treatments showed no preference. The salinity preference seemed to be modified by prior acclimation as well, and juvenile crabs could therefore survive and disperse in the different salinities. Our study helps to explain the complex distribution of juveniles in estuaries and provides arguments for the feasibility of Chinese mitten crabs being reared in low salinity waters. [ABSTRACT FROM AUTHOR]

High temperature is considered to be one of the important causes of mass mortality of diploid and triploid oysters in summer. In order to compare the tolerance adaptability of diploid and triploid oysters to heat stress, the activities of superoxide dismutase activity (SOD), catalase activity (CAT) and contents of malondialdehyde (MDA) and the expression of Hsp70 and metallothionein (MT) genes in diploid and triploid oysters under acute and chronic heat stress were studied. The results showed that the survival rate of diploid oysters was significantly higher than that of triploid oysters under acute and chronic heat stress (p < 0.05). Under acute heat stress, the SOD levels in gills of both diploid and triploid oysters increased significantly from hour 3 (p < 0.05), but there was no significant difference in SOD levels between diploid and triploid oysters at all time points. The SOD level in hepatopancreas of triploid oysters was significantly higher than that of diploid oysters at all time points except 48 h (p < 0.05). The CAT level of diploid and triploid oysters decreased sharply at 48 h and that of diploid oysters was significantly higher than that of triploid oysters (p < 0.05). Under acute heat stress, the increase in MDA content in triploid oysters was significantly higher than that in diploid oysters (p < 0.05). Under acute heat stress, the expression levels of Hsp70 in the gills and hepatopancreas were significantly increased in diploid and triploid oysters (p < 0.05), but increased varies between gills and hepatopancreas. The expression levels of MT in the gills and hepatopancreas were significantly decreased in diploid and triploid oysters (p < 0.05). The results obtained in this study provide physiological and immunological evidence to explain differences in high‐temperature tolerance between diploid and triploid oysters and help us better understand the mass mortality of oysters that occurs during high temperatures in summer. [ABSTRACT FROM AUTHOR]

Background: The deep-sea mussel Gigantidas haimaensis is a representative species from the Haima cold seep ecosystem in the South China Sea that establishes endosymbiosis with chemotrophic bacteria. During long-term evolution, G. haimaensis has adapted well to the local environment of cold seeps. Until now, adaptive mechanisms responding to environmental stresses have remained poorly understood. Results: In this study, transcriptomic analysis was performed for muscle tissue of G. haimaensis in the in situ environment (MH) and laboratory environment for 0 h (M0), 3 h (M3) and 9 h (M9), and 187,368 transcript sequences and 22,924 annotated differentially expressed genes (DEGs) were generated. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, these DEGs were enriched with a broad spectrum of biological processes and pathways, including those associated with antioxidants, apoptosis, chaperones, immunity and metabolism. Among these significantly enriched pathways, protein processing in the endoplasmic reticulum and metabolism were the most affected metabolic pathways. These results may imply that G. haimaensis struggles to support the life response to environmental change by changing gene expression profiles. Conclusion: The present study provides a better understanding of the biological responses and survival strategies of the mussel G. haimaensis from deep sea in situ to the laboratory environment. [ABSTRACT FROM AUTHOR]

Based on an experiment carried out in the north-western Black Sea (Snake Island), the feeding behavior of the Rapa whelk (Rapana venosa Valenciennes, 1846) was analyzed in relation to its size (N = 58; shell height: 30–90 mm). Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) were placed in experimental cages with R. venosa to be used as food. It was found that the size of the prey was determined by the size of the predator. The mussels with a shell length of 20–40 mm were most affected by R. venosa. It was determined that the predator's contribution to the deposition of mussel shells in the bottom sediments is also associated with its size. Feeding intensity varies from 41 mg to 99 mg of the total mass of mussels per 1 g of the total mass of R. venosa per day, depending on the size of the predator. The daily consumption of mussel soft tissue varied from 0.189 g ind.−1 per day−1 in small R. venosa specimens to 0.917 g ind.−1 per day−1 in large predators. Regression equations were obtained between the length and mass of the mussels consumed (total mass, soft tissue mass and shell mass) and the shell height of the predator. [ABSTRACT FROM AUTHOR]

Complex coastal currents control early-stage larval dispersal from intertidal populations, and late-stage settlement patterns, but are often poorly resolved in larval dispersal models. Generally, there is high uncertainty in the timing of larval spawning, which markedly affects larval dispersal. In this study, we describe the physical parameters that induce spawning events in the blue mussel, Mytilus edulis, using a variation of the Condition Index (which relates the mass of meat to the mass of the shell) as a proxy. We developed a high-resolution Eulerian coastal hydrodynamic model, coupled with a Lagrangian particle tracking model, to quantify the potential dispersal of early-stage mussel larvae based on differing spawning dates obtained from field data. Our results showed that (1) the timings of larval spawning cannot be explained solely by 'thermal shocks' in the sea or air temperatures (i.e. fluctuations in temperature causing stress); (2) larger spawning events generally occurred during neap tides; (3) the simulated larval dispersal was largely but not always predicted by averaged current pathways (calculated over two weeks period); and (4) simulated self-recruitment was low at sites associated with strong tidal currents. These results have important implications for shellfisheries stock management and sustainability. Specific to this study, simulated mussels from shellfishery beds off North Wales dispersed more than 25 km in one week and so could feasibly contribute to the wider population throughout the northern part of the Irish Sea. [ABSTRACT FROM AUTHOR]

If this is the case, restoration and conservation of these threatened oyster reefs may enhance ontogenetic movement opportunities for the species by providing key juvenile habitats, which could further aid in the long-term stability and protection of blue groper populations. Conservation, demography, life history, recruitment, charismatic megafauna, estuarine ecosystem, intertidal reef, temperate reef, threatened species This observation of an iconic and threatened species using threatened oyster reefs as a juvenile habitat is significant, not only because it enhances our understanding of I A. viridis i and their ontogenetic movement, but because of the opportunity that this presents for the engagement and funding of ongoing and future oyster reef restoration projects. Keywords: charismatic megafauna; conservation; demography; estuarine ecosystem; intertidal reef; life history; recruitment; temperate reef; threatened species EN charismatic megafauna conservation demography estuarine ecosystem intertidal reef life history recruitment temperate reef threatened species 1 5 5 12/05/22 20221201 NES 221201 Understanding the life cycle and the demography of individual species is critical for the management of threatened populations and integral to understanding the ecology of various ecosystems and habitats (Kimirei et al., [11]; Perez & Munch, [15]). [Extracted from the article]

Okadaic acid (OA), one of marine biotoxins produced by several species of dinoflagellates, can accumulate in marine animals. The consumption of OA-contaminated seafood can cause diarrhoeic shellfish poisoning. Many countries have established regulatory restriction to limit the level of OA in seafood. In the present study, we report a highly sensitive monoclonal antibody (mAb) against OA produced by a new immunogen. Two monoclonal hybridoma cell lines (M8 and M12) that producing mAb with the best sensitivity and specificity were obtained. The obtained mAb-M12 was used to develop an indirect competitive ELISA (icELISA) with 50% inhibition concentrations of 0.15 ng mL−1 and a working range of 0.02–2.74 ng mL−1. The developed icELISA was more sensitive than the previous reports. HPLC-MS confirmed the accuracy and the working range of icELISA, suggesting that the developed icELISA is suitable for the rapid detection of OA in oysters and green mussels. [ABSTRACT FROM AUTHOR]

This study focused on the effect of common natural diets, scadfish and squid on the growth performance, morphology, histology and fatty acids of ovary and hepatopancreas of female orange mud crabs, Scylla olivacea. Twenty individuals of newly mature crabs (body weight = 69.21 ± 2.19 g, carapace width = 7.18 ± 0.07 cm) with 10 individuals per treatment were cultured for 60 days with ambient water parameters. Twenty individuals of control crabs were also collected from the wild. The highest body weight gain (BWG), carapace width gain (CWG), gonadosomatic index (GSI) as well as oocyte and tubule diameter were recorded during the captivity, with the mud crabs fed with scadfish leading (BWG = 36.58%, CWG = 14.90%, GSI = 0.47%, oocyte diameter = 47.19 μm, tubule diameter = 167.82 μm). Likewise, high concentrations of ∑PUFA, ∑EPA, ∑DHA and ∑n3 were reported in scadfish‐fed crabs compared to both squid‐fed and wild‐caught crabs (p < 0.05). In contrast, lower fatty acids were noted in the hepatopancreas of crabs from all treatments, suggesting an occurrence of nutrient transfer from the hepatopancreas to the ovaries. Overall results concluded that scadfish is preferred as the main diet for crabs in captivity. [ABSTRACT FROM AUTHOR]

Klebsiella pneumoniae is a common conditional pathogen found in natural soil water sources and vegetation and can infect invertebrates, vertebrates, and plants. In this study, we isolated K. pneumoniae from the hepatopancreas of the Chinese mitten crab (Eriocheir sinensis) for the first time and then we analysed its effects of on the histopathological changes, the transcriptome of the hepatopancreas, and the gut microbiota of this crab species. The findings of this study showed that K. pneumoniae infection has led to significant structural changes in the hepatopancreas, such as the production of vacuolated tissue structures, disorganized cell arrangement, and lysis of some hepatopancreatic cells. Also, the infection caused activation of the antioxidant-related enzymes such as SOD and CAT by inducing oxidative stress. The transcriptome of the hepatopancreas identified 10,940 differentially expressed genes (DEGs) in the susceptible (SG) groups and control (CG) groups, and 8495 DEGs in the SG groups and anti-infective (AI) groups. The KEGG pathway revealed upregulated DEGs caused by K. pneumoniae infection that involved in the immune response and apoptotic functional pathways, and also downregulated DEGs involved in the digestive absorption, metabolic, and biosynthetic signaling pathways. Meanwhile, metagenics sequencing revealed that at the phylum, class, order, family, and genus levels, K. pneumoniae infection altered the composition of the gut microbiota of E. sinensis , through increasing the abundance of Prolixibacteraceae , Enterobacterales , and Roseimarinus and decreasing the abundance of Alphaproteobacteria. The flora structure has also been changed between the SG and AI groups, with the abundance of Firmicutes , Erysipelotrichales , and Erysipelotrichaceae that were significantly decreased in the SG groups than in the AI groups. But, the abundance of Acinetobacter was considerably higher than in the AI group. In summary, K. pneumoniae infection induced oxidative stress in E. sinensis , triggered changes in immune-related gene expression, and caused structural changes in the gut microbiota. This study provides data to support the analysis of bacterial infection probes in several crustacean species. • K. pneumoniae K57 can infect E. sinensis and leads to hepatopancreatic vacuolation. • RNA transcriptome has been changed during K. pneumoniae infection in E. sinensis hepatopancreas. • K. pneumoniae infection affects the gut microbiota structure of E. sinensis. [ABSTRACT FROM AUTHOR]

Oysters are commercially important intertidal filter-feeding species. Mass mortality events of oysters often occur due to environmental stresses, such as exposure to fluctuating temperatures, salinity, and air, as well as to metal pollution and pathogen infection. Here, RNA-seq data were used to identify shared and specific responsive genes by differential gene expression analysis and weighted gene co-expression network analysis. A total of 18 up-regulated and 10 down-regulated shared responsive genes were identified corresponding to five different stressors. Total 27 stressor-specific genes for temperature, 11 for salinity, 80 for air exposure, 51 for metal pollution, and 636 for Vibrio mediterranei pathogen stress were identified in oysters. Elongin-β was identified as a crucial gene for thermal stress response. Some HSP70s were determined to be shared responsive genes while others were specific to thermal tolerance. The proteins encoded by these stress-related genes should be further investigated to characterize their physiological functions. In addition, the uncharacterized proteins and ncRNAs that were identified may be involved in species-specific stress-response and regulatory mechanisms. This study identified specific genes related to stressors relevant to oyster cultivation. These findings provide useful information for new selective breeding strategies using a data driven method. [Display omitted] • Pacific oysters are exposed to various biotic and abiotic stressors. • Key environmental stress-responsive genes in oysters were investigated. • Differentially regulated genes specific to stressors were identified. • Such genes could be used as biomarkers for monitoring and breeding oyster. [ABSTRACT FROM AUTHOR]

Rice crab co-culture is a new integrated farming model in China. The application of triazole plant growth regulators (PRGs) is often used as an advantageous option to combat rice lodging. However, there is still a gap regarding the toxicity of these PRGs on the growth and development of the Chinese mitten crab (Eriocheir sinensis, E. sinensis). Here the effect of triazoles (paclobutrazol and uniconazole) on the molting mechanism of E. sinensis was investigated. Monitoring of regulatory genes associated with molting showed that the two PRGs were found to inhibit the expression of ecdysteroid hormone (EH), ecdysteroid receptors gene (EcR), and retinoid X receptors gene (RXR) and induce secretion of molt-inhibiting hormone (MIH) gene. In addition, the activities of chitinase (CHIA) and N-acetyl-β- d -aminoglucosidase (β-NAGase) were also inhibited by exposure to PRGs. Exposure to PRGs also elevated the mRNA expression of the growth-related myostatin gene (MSTN). These results revealed that there is a long-term risk of exposure to triazoles PRGs that may inhibit molting and affect normal development and immune system of E. sinensis. [Display omitted] • Effects of triazole plant growth regulators (RPGs) on E. sinensis were researched. • Paclobutrazol and uniconazole were not significantly acutely toxic to E. sinensis. • Triazole RPGs show endocrine disruptive ability in inhibiting molting in E. sinensis. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate hepatitis A virus (HAV) and hepatitis E virus (HEV) contamination in mussels (Mytilus galloprovincialis) from Cherrat estuary (Moroccan Atlantic Coast), Morocco. In total, 52 samples (n = 12 mussels/each) were collected at four sites in the estuary, monthly, between March 2019 and March 2020. HAV and HEV were detected by real-time reverse transcription polymerase chain reaction (RT-PCR) according to the ISO/TS 15216 method. HAV was detected in 46.15% of analyzed samples. Conversely, HEV was not detected in any sample. Moreover, the HAV detection rate was significantly associated with seasonal rainfall variations. This qualitative study on HAV and HEV contamination highlights the interest of studying mussel samples from wild areas. As HAV presence in mussels represents a potential health risk, viral contamination surveillance of mussels is necessary to protect consumers. HAV shellfish contamination must be monitored at Cherrat estuary because of the role played by shellfish as HAV reservoirs and/or vehicles in fecal-oral HAV transmission. [ABSTRACT FROM AUTHOR]

Ocean acidification upwelling events and the resulting lowered aragonite saturation state of seawater have been linked to high mortality of marine bivalve larvae in hatcheries. Major oyster seed producers along North America’s west coast have mitigated impacts via seawater pH buffering (e.g., addition of soda ash). However, little consideration has been given to whether such practice may impact the larval microbiome, with potential carry-over effects on immune competency and disease susceptibility in later-life stages. To investigate possible impacts, Pacific oysters (Crassostrea gigas) were reared under soda ash pH buffered or ambient pH seawater conditions for the first 24 h of development. Both treatment groups were then reared under ambient pH conditions for the remainder of the developmental period. Larval microbiome, immune status (via gene expression), growth, and survival were assessed throughout the developmental period. Juveniles and adults arising from the larval run were then subjected to laboratory-based disease challenges to investigate carry-over effects. Larvae reared under buffered conditions showed an altered microbiome, which was still evident in juvenile animals. Moreover, reduced survival was observed in both juveniles and adults of the buffered group under a simulated marine heatwave and Vibrio exposure compared with those reared under ambient conditions. Results suggest that soda ash pH buffering during early development may compromise later-life stages under stressor conditions, and illustrate the importance of a long-view approach with regard to hatchery husbandry practices and climate change mitigation. IMPORTANCE Shellfish industries are threatened worldwide by recurrent summer mortality events. Such incidences are often associated with Vibrio disease outbreaks, and thus, it is critical that animals are able to mount sufficient immune responses. The oyster immune system is linked to the microbiome which is laid down during early developmental stages. Consequently, shellfish hatcheries play a key role with regard to shaping the immune competency of later-life stages. This study represents the first in-depth examination of whether the adoption of seawater pH buffering practice by hatcheries for mitigation of ocean acidification may alter the larval microbiome, and thus, have repercussions for adult susceptibility to summer mortality events. Findings demonstrate that even minimal buffering results in a changed microbiome which is paralleled by increased mortality of later-life stages under Vibrio and temperature stressors, highlighting the importance of the hatchery environment with regard to shaping resilience to summer mortality events. [ABSTRACT FROM AUTHOR]