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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]

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]

Simple Summary: As a filter-feeding and sessile invertebrate living in estuaries and intertidal areas, Crassostrea gigas must cope with and adapt to a dynamic and changeable environment. Vibrio alginolyticus is a Gram-negative bacterium that is widespread in oceans and estuaries, and is one of the main Vibrio species that cause oyster disease. In this study, we used transcriptome sequencing to help us better understand how the giant oyster adapts to pathogen-rich environments. By focusing on the gills, which play a crucial role in the immune response, we aimed to shed light on the molecular processes underlying the interaction between the oyster and the pathogen. Over the years, oysters have faced recurring mass mortality issues during the summer breeding season, with Vibrio infection emerging as a significant contributing factor. Tubules of gill filaments were confirmed to be in the hematopoietic position in Crassostrea gigas, which produce hemocytes with immune defense capabilities. Additionally, the epithelial cells of oyster gills produce immune effectors to defend against pathogens. In light of this, we performed a transcriptome analysis of gill tissues obtained from C. gigas infected with Vibrio alginolyticus for 12 h and 48 h. Through this analysis, we identified 1024 differentially expressed genes (DEGs) at 12 h post-injection and 1079 DEGs at 48 h post-injection. Enrichment analysis of these DEGs revealed a significant association with immune-related Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. To further investigate the immune response, we constructed a protein–protein interaction (PPI) network using the DEGs enriched in immune-associated KEGG pathways. This network provided insights into the interactions and relationships among these genes, shedding light on the underlying mechanisms of the innate immune defense mechanism in oyster gills. To ensure the accuracy of our findings, we validated 16 key genes using quantitative RT-PCR. Overall, this study represents the first exploration of the innate immune defense mechanism in oyster gills using a PPI network approach. The findings provide valuable insights for future research on oyster pathogen control and the development of oysters with enhanced antimicrobial resistance. [ABSTRACT FROM AUTHOR]

Settlement is a critical period in the life cycle of marine invertebrates with a planktonic larval stage. For reef-building invertebrates such as oysters and corals, settlement rates are predictive for long-term reef survival. Increasing evidence suggests that marine invertebrates use information from ocean soundscapes to inform settlement decisions. Sessile marine invertebrates with a planktonic stage are particularly reliant on environmental cues to direct them to ideal habitats. As gregarious settlers, oysters prefer to settle amongst members of the same species. It has been hypothesized that oyster larvae from species Crassostrea virginica and Ostrea angasi use distinct conspecific oyster reef sounds to navigate to ideal habitats. In controlled laboratory experiments we exposed Pacific Oyster Magallana gigas larvae to anthropogenic sounds from conspecific oyster reefs, vessels, combined reef-vessel sounds as well as off-reef and no speaker controls. Our findings show that sounds recorded at conspecific reefs induced higher percentages of settlement by about 1.44 and 1.64 times compared to off-reef and no speaker controls, respectively. In contrast, the settlement increase compared to the no speaker control was non-significant for vessel sounds (1.21 fold), combined reef-vessel sounds (1.30 fold), and off-reef sounds (1.18 fold). This study serves as a foundational stepping stone for exploring larval sound feature preferences within this species. [ABSTRACT FROM AUTHOR]

Simple Summary: A new interspecific backcross ([(Crassostrea hongkongensis ♀ × C. gigas ♂) ♂ × C. hongkongensis ♀]) variety was bred by the South China Sea Institute of Oceanology and named "South China No. 1". This study aims to explore the effects of stocking density on the growth performance of "South China No. 1", and compare the growth performance and genetic diversity to that of C. hongkongensis in Beibu Gulf. The results showed that oysters bred under a stocking density of 20 oysters/substrate had better growth manifestation. It was found that the shell height and total weight of "South China No. 1" cultured in Fangchenggang were significantly higher than that of those in Beihai and Qinzhou from September 2018 to November 2018. In addition, the shell height and shell width of "South China No. 1" were significantly higher than that of C. hongkongensis. In the Hardy–Weinberg equilibrium test, for the seven populations and ten microsatellites, in 10 of the 70 groups, the segregation distortion was significant. These results suggest that a stocking density of 20 oysters/substrate can promote the shell height, shell width and total weight of "South China No. 1". Fangchenggang is a suitable place to cultivate the "South China No. 1" breed according to the total weight and sum of all algal genus abundances. Crassostrea hongkongensis is an economically important bivalve found in various parts of the South China Sea. A new interspecific backcross ([(Crassostrea hongkongensis ♀ × C. gigas ♂) ♂ × C. hongkongensis ♀]) variety was bred by the South China Sea Institute of Oceanology which named "South China No. 1". This study aims to explore the effects of stocking density on the growth performance of "South China No. 1", compared their growth performance and genetic diversity to C. hongkongensis, and found the best place breeding site for "South China No. 1" in Beibu Gulf. The results showed that stocking a density of 20 oysters/substrate can significantly increase the shell height, shell width, total weight, survival rate, daily shell height gain and daily body mass gain. It was found that the shell height and total weight of "South China No. 1" cultured in Fangchenggang were significantly higher than that of those in Beihai and Qinzhou from September 2018 to November 2018. Similarly, the shell width of oysters in Fangchenggang and Qinzhou was also significantly higher in September 2018, and the interaction between site and stocking density had significant effects on the shell width in March 2018 and November 2018. In addition, the shell height and shell width of "South China No. 1" were significantly higher than that of C. hongkongensis in all three sites. At all three sites, the phytoplankton community structure was mostly dominated by Bacillariophyta. In the Hardy–Weinberg equilibrium test, for the seven populations and ten microsatellites, in 10 of the 70 groups, the segregation distortion was significant. These results suggest that a stocking density of 20 oysters/substrate can promote the shell height, shell width and total weight of "South China No. 1" in Beibu Gulf, China. "South China No. 1" has better growth performance compared with C. hongkongensis. Fangchenggang is a suitable place to cultivate the "South China No. 1" breed according to the total weight and sum of all algal genus abundances. The results of this study can be used as a reference to further understand the stocking density and genetic diversity of the "South China No. 1" breed in Beibu Gulf, China. [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]

Crassostrea ariakensis (Fujita, 1913) is one of the most important economic and ecological oysters that is naturally distributed along the coast of Asia, separated by the Yangtze River estuary. They are usually compared as different populations, while there is no consensus on whether C. ariakensis in northern and southern areas should be considered as two species or subspecies. Here, we analyzed morphological characteristics, COI, 16s rRNA, mitogenome sequences, and species delimitation analysis (ASAP and PTP) to resolve the intraspecific taxonomic status of the C. ariakensis. Phylogenetic and ASAP analysis highlight that C. ariakensis was divided into N-type and S-type. PTP was unable to differentiate between the two types of C. ariakensis. The divergence time of N-type and S-type C. ariakinsis is estimated to be 1.6 Mya, using the relaxed uncorrelated lognormal clock method. Additionally, significant morphological differences exist between the two groups in terms of the adductor muscle scar color. Despite these differences, the COI (0.6%) and 16S rRNA (0.6%) genetic distance differences between N-type and S-type C. ariakensis has not yet reached the interspecific level. These results suggest that N-type and S-type C. ariakensis should be treated as different subspecies and renamed as C. ariakensis ariakensis subsp. nov and C. ariakensis meridioyangtzensis subsp. nov. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) pollution has wreaked havoc on biodiversity and food safety globally. The false ingestion of MPs causes harmful effects on organisms, resulting in a decline in biodiversity. The present review comprehended the current knowledge of MP contamination in Crustacea and Mollusca from 75 peer‐reviewed articles published in Asia between 2015 and 2023. A total of 79 species (27 Crustacea and 52 Mollusca) have been recorded to be contaminated with MPs. Out of the total 27 species of Crustacea, Metopograpsus quadridentatus (327.56 MPs/individual) and Balanus albicostatus (0.42 MPs/individual) showed the highest and lowest contamination, respectively. Out of the total 52 species of Mollusca, Dolabella auricularia (2325 MPs/individual) and Crassostrea gigas and Mytilus edulis (0.2 MPs/individual) showed the highest and lowest contamination, respectively. In terms of country‐wise MP contamination, China has the highest number of contaminated species in both phylums among Asia. Findings of pollution indices revealed a very high risk of MP contamination in all the countries. Fiber was reported predominantly in both groups. Blue and black‐colored MPs having <500 μm and <500 μm–1 mm size were found dominantly in Crustacea and Mollusca, respectively. Polypropylene was recorded as the dominant plastic polymer in both Crustacea and Mollusca. In essence, this review has provided a comprehensive insight into MP concentration in Crustacea and Mollusca of Asia, highlighting variations among species and geographic locations. This understanding is crucial for tackling urgent environmental challenges, safeguarding human health, and promoting global sustainability initiatives amid the escalating issue of plastic pollution. Practitioner Points: Microplastic pollution has created havoc on biodiversity and food safety.A total of 27 and 52 species of crustaceans and Mollusca have been recorded to be contaminated with MPs.Metopograpsus quadridentate and Dolabella auricularia have shown higher MPs contamination.Polypropylene was recorded as the dominant plastic polymer in both crustacean and Mollusca.Findings of pollution indices revealed a very high risk of MP contamination in all the countries. [ABSTRACT FROM AUTHOR]

Crassostrea is the most farmed oyster genus worldwide and has significant economic and social impacts with environmental benefits. Hatchery oyster seed production is a highly costly phase, and a fluidized nursery system can help reduce this cost and reduce seed production time. The present study evaluated the survival and growth of two oyster species (Crassostrea gasar and Crassostrea gigas) in a fluidized bed bottle nursery system. With C. gasar, two experiments were performed; one tested three stocking densities and the other three bialgae diets. With C. gigas, one experiment with a bialgae and monoalgae in an initial bottle occupation of 8.8% produced more seeds per bottle, but an initial bottle occupation of 2.2% produced bigger seeds. Also, the experiment with C. gasar and with C. gigas tested diets did not affect seed survival, but the diets with bialgae I. galbana and N. oculate promoted more seed growth. The fluidized bed bottle nursery system developed for this study was adequate for the seeds of the oysters C. gasar and C. gigas in the nursery phase. [ABSTRACT FROM AUTHOR]

Caspase-8, a member of the caspase family, is an initiating caspase and plays a crucial role in apoptosis. In this study, the full-length cDNA of caspase8-like (CASP8-like) was isolated from Crassostrea hongkongensis (C. hongkongensis) by RACE-PCR. ChCASP8-like contained a 1599-bp open reading frame (ORF) encoding 533 amino acids with two conserved death effector domains (DEDs) and a cysteine aspartase cysteine structural domain (CASc). Amino acid sequence comparison showed that ChCASP8-like shared the highest identity (85.4%) with CASP8-like of C. angulata. The tissue expression profile showed that ChCASP8-like was constitutively expressed in gills, hepatopancreas, mantle, adductor muscle, hemocytes and gonads, and was significantly upregulated in hemocytes, hepatopancreas and gills under hyper-salinity stress. The apoptosis-related genes, including ATR, CHK1, BCL-XL, CASP8-like, CASP9 and CASP3, were significantly activated by hyper-salinity stress, but were remarkably inhibited by ChCASP8-like silencing. The caspase 8 activity was increased by 1.7-fold after hyper-salinity stress, and was inhibited by 9.4% by ChCASP8-like silencing. Moreover, ChCASP8-like silencing clearly alleviated the apoptosis resulting from hyper-salinity stress. These results collectively demonstrated that ChCASP8-like played a crucial role in inducing apoptosis against hyper-salinity stress. [ABSTRACT FROM AUTHOR]

Crassostrea gasar is a bivalve mollusk of economic interest in the Amazon estuary, because it displays good zootechnical performance and nutritional value. However, there is still a gap in the literature regarding studies on basic biology, especially spermatogenesis at the ultrastructural level. This study aimed to describe for the first time the male gonad development. Gonad fragments were analyzed using light microscopy and transmission and scanning electron microscopy. The ultrastructural analysis of the gonadal tubule showed two distinct cell populations: support cells and the cells of the spermatogenic lineage. Regarding the ultrastructural aspects, support cells were characterized by an irregular shape, sparse electron-dense cytoplasm, and a large nucleus with condensed chromatin; and two types of spermatogonia were seen (A and B); spermatocytes I where it was possible to characterize four stages of prophase I, namely leptotene, zygotene, pachytene, diplotene; spermatocytes II showing a reduction in cytoplasmic and condensed chromatin. Spermatids were classified into three stages of development: early, middle, and late. Mature spermatozoa are of the primitive type and have a cone-shaped head with a discoidal acrosome, a midpiece formed by four mitochondria, and a long flagellum. This information can help establish phylogenetic relationships between species of the genus Crassostrea. In addition, these findings can support conservation biology by developing and implementing biotechnological approaches, such as cryopreservation, and contributing to commercial-scale cultivation in the Amazon region. [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]

The mangrove oyster Crassostrea rhizophorae is identified as a potentially valuable species for tropical aquaculture, however, information on the physiological mechanisms of reproduction under laboratory conditions for this species is limited. This study investigated the effects of salinity at different concentrations (15, 20, 25, 30, 35, and 40 g/L) on the induction of germinal vesicle breakdown (GVBD) of oocytes obtained through stripping, the release of polar bodies (PB1 and PB2), and the larval development of the mangrove oyster. The results revealed a relationship between salinity and the percentage of GVBD, with the most effective range being 30–40 g/L within the hydration time frame between 70 and 120 min. The release of 50 % of PB1 was detected within this salinity range, while for the release of 50 % of PB2, the saline treatments of 35 and 40 g/L showed the best results. Overall, the salinity range of 30–40 g/L is suggested as the most suitable of polyploidy induction methodologies through the retention of PB1 or PB2. Regarding larval hatching, while salinities between 25 and 40 g/L presented similar percentages, at 15 g/L no hatching was observed. This study demonstrated that salinity is a key factor in early pre- and post-fertilization stages for the successful reproduction of mangrove oyster in hatcheries and that the percentages of oocyte maturation and artificial fertilization can be optimized by adjusting salinity. • Salinity significantly influenced the timing of germinal vesicle breakdown (GVBD). • Salinity influences the process of polar bodies (PB1 and PB2) release synchronization. • Hydrated oocytes at 35 and 40 g L exhibited higher percentages of GVBD, PB1 and PB2. • Higher salinities are crucial for the early pre- and post-fertilization stages, but not at later stages (larval hatching). [ABSTRACT FROM AUTHOR]

Contaminants compounds like Heavy Metals and Polycyclic Aromatic Hydrocarbons (PAH's) are primarily sourced from industrial and urban areas. As pollutants, these chemical elements and compounds are potentially toxic and present the capacity to negatively impact the ecosystem, especially the most sensitive ones such as estuaries. Bivalves' species have been successfully utilized as monitoring tools to evaluate pollutants bioaccessibility around the globe. The present study assessed heavy metals (Zn, Cd, Ni, Fe, Cr, Cu and Pb), As and PAH's levels in two mollusk species (Perna perna and Crassostrea rhizophorae) from Santos Estuarine System, in São Paulo State, in order to compare the effectiveness of each species in the biomonitoring process. According to the obtained data, Perna perna mussels may be better indicators of environmental pollution than Crassostrea rhizophorae oysters for some metals (Iron and Nickel) and hydrocarbons. On the other hand, in the present study, oysters had a higher capacity for retaining zinc, copper, and cadmium, due to their peculiar physiological characteristics. [ABSTRACT FROM AUTHOR]

The Pacific oyster Crassostrea gigas is one of the most commercially important aquaculture species worldwide. The occurrence of inbreeding is common in the breeding practice of oysters due to limited population size, successive high selection pressure, and genetic drift. To determine the potential effects of inbreeding on the potential of genetic improvement for fast growth of oysters, genetic parameters of growth traits in the 7th to 9th generation of the orange-shell strain (a typical inbred population) were estimated. At the grow-out stage, the average genetic gain (GG), selection response (SR), and realized heritability ( h R 2 ) for shell height were 6.06–7.06%, 0.43–0.50, and 0.24–0.27, respectively. Meanwhile, the average GG, SR, and h R 2 for body weight were 6.03–7.36%, 0.38–0.41, and 0.21–0.22. There were no significant differences in the corresponding genetic parameters among the three generations (P > 0.05). Genetic parameters were estimated for an unselected population of C. gigas that served as a control group and were significantly higher than those of the orange-shell strain (P < 0.05). The results of this study suggest that inbreeding reduced the potential for genetic improvement of the rapid growth of oysters. However, some easy-to-operate and low-cost measures including the large size of broodstock, balanced sex ratio, and artificial spawning have been applied to the mass selection of the orange-shell strain, which prevents the situation from getting worse. These results will contribute to a better understanding of the negative effects of inbreeding on C. gigas and the management of inbreeding in shellfish breeding programs. [ABSTRACT FROM AUTHOR]

This study aimed to compare the growth and survival of Crassostrea gigas spat at four sites (Sambaqui (SBQ), Paraíso das Ostras (PAR), Atlâtico Sul (ATL), and Cia das Ostras (CDO)) in Brazil. Batches of spat were reared in the summer and winter of 2018 and the summer of 2019 for two month periods. SBQ site had higher total particulate matter and particulate inorganic matter values than those observed at the other sites. The salinity at the PAR site was higher than that found at the other sites, but the temperature was lower. No differences in survival were observed among the sites in the summer or winter of 2018; however, in the summer of 2019, there were significant differences. Shell height was higher during warmer seasons than during winter. In conclusion, the SBQ and ATL sites were found to have better conditions for spat cultivation than the PAR and CDO sites. [ABSTRACT FROM AUTHOR]

The mangrove oyster (Crassostrea) is one of the most common bivalves found on the Brazilian coast, widely used in artisanal fisheries. Oysters are dioecious with external reproduction, typically found in estuarine environments. The present study aimed to identify the population aspects of Crassostrea in different fishing locations in northeastern Brazil. The study area was the Acaú-Goiana Extractive Reserve, a protected area focused on the development of artisanal fisheries. Oysters were collected during low tide at three sampling points, where their removal from mangrove roots was carried out, during May, July, September, November 2021, and January and March 2022. In the laboratory, biometric measurements were conducted, and for the months of May and November 2021 histological preparations to study the reproductive cells. Biometric measurements were significantly higher in the dry season at all sampling points. The sex ratio was M = 0.38, F = 0.62, for May, and M = 0.30, F = 0.69, for November. The biometric and reproductive data obtained can support the development of management strategies, including a rotation plan between collection sites and the establishment of a minimum size for fishing. Here we recommend a minimum size of 20 mm shell length (SL) or larger for fishing. [ABSTRACT FROM AUTHOR]

Invasive marine species (IMS) are a major anthropogenic threat to global marine environments. To mitigate the threat, Australian federal and state governments have developed detailed quarantine programs to minimise IMS introductions, supported by monitoring programs to detect any IMS that penetrated the quarantine barriers. Considerable shipping movements occur between the Pilbara region of northwestern Australia and southeast Asia where a number of potential IMS oysters occur. eDNA techniques are being developed to rapidly scan biofouling and other samples for potential IMS, but there is limited information on oysters present in the Pilbara. We collected intertidal oysters in and near Pilbara ports and identified them using DNA sequences to determine if any IMS are present and to provide a baseline to prevent false positive results for IMS by native species. Only three species were detected: native Saccostrea lineage A and S. scyphophilla, both widespread in the Pilbara, and Talonostrea sp. nov. which had not previously been reported from the Pilbara. No IMS oysters were found. The study provides a solid basis for monitoring for any future occurrences of IMS oyster species in the Pilbara, an area with a very high known shallow water marine biodiversity, but where only a single IMS is known to occur. [ABSTRACT FROM AUTHOR]

Kumamoto oysters (Crassostrea sikamea) are important marine aquaculture shellfish because of their taste and round shell shape. Due to its small size, selective breeding is required to improve its market size, but there are no reports on traits suitable for direction selection and reproductive productivity of Kumamoto oysters of different ages. In this study, path analysis and one-way ANOVA were used to explore the influential indices of oyster body weight and fecundity. The results showed that shell height was the main factor affecting the body weight of Kumamoto oysters at one-year-old and two-year-old, followed by shell length. Body weight was the main factor influencing fecundity, and shell height showed a significant correlation with fecundity. Therefore, shell height should be considered the first parameter for selection when selecting Kumamoto oysters for body weight as the direct selection target. When one-year-old and two-year-old Kumamoto oysters were selected as parents from Xiangshan Bay, hatching parameters and growth parameters of F1 generation larvae were measured. The fecundity and egg diameters were 1.72 × 106 and 46.60 ± 3.62 µm, respectively, which were significantly greater than one-aged oysters (5.86 × 105, 40.26 ± 3.52 µm). The hatching parameters (fertilized egg size, fertilization rate, and hatching rate) and larval growth performance (D-stage veliger and veliger) were similar and did not differ significantly (P > 0.05), and after metamorphosis, there was also no significant difference in shell height size at 40 days of age (P > 0.05). Therefore, there was no significant effect of age on reproduction, larval development, and the early growth of Kumamoto oysters. These results could provide a basis for parental sources and proper traits for Kumamoto oyster selection, which is beneficial to developing and utilizing this excellent germplasm resource. [ABSTRACT FROM AUTHOR]

Hong Kong oysters (Crassostrea hongkongensis) are an important marine bivalve with nutritional and commercial value. The expanded off-bottom farming scale in recent years makes the oysters more susceptible to exposure to abiotic stresses, such as salinity stress, an important environmental factor that has been proven to have significant effects on oyster growth and development. However, the molecular mechanism is still unclear. Cyclin E is an important protein in the process of cell cycle regulation that is indispensable for propelling G1/S phase transition in a dose-dependent manner. In order to investigate whether the salinity stress affects cyclin E expression in oysters, the cDNA sequence of C. hongkongensis cyclin E (Ch-CCNE) was isolated from a gill cDNA library, and the 2.8 kbp length cDNA fragment contained a complete open reading frame (ORF) encoding 440 amino acid residues. Ch-CCNE mRNA was highly expressed in the gonad and low in the adductor mussel, mantle, gill, labial palp, and digestive gland. The recombinant CCNE protein was expressed and purified in a pET32a(+)-CCNE/Escherichia coli BL21(DE3) system via IPTG induction and was used for generating mice anti-Ch-CCNE antiserums. Western blot analysis showed that the CCNE protein in the gill was maintained at low expression levels under either hypo- (5 ppt) or hyper- (35 ppt) salinity, and could be produced at high levels under appropriate salinity during a 10-day exposure period. The immuno-localization indicated that the Ch-CCNE protein was distributed in the nucleus. These results suggested that either hypo- or hyper-salinity stress could inhibit the CCNE expression of Hong Kong oysters and their negative impact on cell division and proliferation. [ABSTRACT FROM AUTHOR]

The sterility advantages of triploids make them paramount for oyster aquaculture. Tetraploids are always used as male parents for triploid industrial breeding in current hatcheries, thus they are the core asset for triploid oyster culture. The oyster Crassostrea angulata is the most productive oyster species in China. However, the optimal conditions for tetraploid induction have never been examined. In this study, we investigated the effectiveness of three induction methods (Method I, 2n ♀ × 2n ♂ + inducer abbreviated as DD + ind; Method II, 3n ♀ × 2n ♂ + inducer abbreviated as TrD + ind; Method III, 2n ♀ × 4n ♂ + inducer abbreviated as DT + ind) and three inducers (salinity; cytochalasin B, CB; and 6-dimethylaminopurine, 6-DMAP) for tetraploid induction in C. angulata. The optimal induction conditions for the three induction methods were a CB concentration of 0.5 mg/L treated for 20 min, 0.75 mg/L CB for a constant induction treatment of 20 min and 6-DMAP at a concentration of 100 mg/L for 20 min, respectively. When the optimal induction conditions were applied to a single pair of oysters, the D-larval tetraploid rate for the three methods were 18.93 ± 1.46%, 58.32 ± 1.03% and 51.61 ± 1.37%, respectively. After 30 days, the survival rates of the experimental groups were only 10.36 ± 2.51%, 28.07 ± 2.03% and 21.99 ± 1.27%, respectively, at day 30. The tetraploid rates in DD + ind and DT + ind were both decreased significantly over time, but they still reached 11.81% and 21.99% at 30 days, and 8% and 16% at day 180, respectively. Tetraploid rates in TrD + ind were 58.32 − 71.28% at the larval stage and 80% at day 180. In summary, despite very different induction rates, surviving tetraploids of C. angulata could be obtained in all three methods. Method II (TrD + inducer) was regarded as the optimal method to induce C. angulata tetraploids, and the optimal induction condition was a CB concentration of 0.75 mg/L and treated for 20 min under this method. [ABSTRACT FROM AUTHOR]

An important pathogen of concern for Pacific oyster growers in the USA is ostreid herpesvirus 1 (OsHV‐1). Currently, oyster stocks exist that are tolerant to OsHV‐1; however, it is uncertain if a trade‐off exists between their tolerance to OsHV‐1 and their growth in different environments. To investigate any potential trade‐offs, Pacific oyster families with varying levels of OsHV‐1 tolerance were grown in a bay where OsHV‐1 is endemic (Tomales Bay, CA) and in a bay where OsHV‐1 is absent (Willapa Bay, WA). In Tomales Bay, we found that oysters from OsHV‐1 tolerant families grew faster than oysters from OsHV‐1 susceptible families, while in Willapa Bay, no statistically significant difference in growth was found between oyster families with different levels of OsHV‐1 tolerance observed in Tomales Bay. These findings indicate that Pacific oysters bred to be tolerant to OsHV‐1 would not be expected to have a longer time‐to‐market regardless of the presence of OsHV‐1 in the growing environment. [ABSTRACT FROM AUTHOR]

The article explores an ambitious U.S. project aiming to sample over 50 animal species to understand how Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) moves between wildlife and humans, focusing on deer as potential hosts and the implications of viral transmission for both species. Topics discussed include the prevalence and transmission dynamics of the virus in various wildlife populations to mitigate potential risks to human health.

Simple Summary: The parasites of the genus Polydora spp. cause great damage to oyster broodstocks, both Cupped (Crassostrea gigas) and Flat oysters (Ostrea edulis), as they excavate channels in the shell of the mollusk, forming mud blisters. The infestation negatively affects the oysters' welfare, as it influences respiratory activity, induces oxidative stress in the animal, and impacts the productivity of the farm, as heavily parasitized mollusks cannot be commercialized. With the aim of obtaining a non-invasive assessment of the presence of this parasite, the use of two diagnostic methods, magnetic resonance imaging and X-ray computed tomography, was investigated. These methods have been shown to be effective in diagnosing the infestation, and although the current costs of their application are prohibitive for production reality, the possibility of analyzing or evaluating remediation techniques on large stocks of animals offers interesting perspectives. The Polichete worms of the genus Polydora are considered very destructive for oysters, excavating channels in their shell and inducing oysters to create mud blisters in response to the irritation, interfering with their physiology and ethology. The parasite also causes important economic damage for oyster farmers, as products with a high degree of infestation cannot be commercialized. The present study aims to evaluate whether two non-invasive advanced diagnostic techniques, computed tomography scans (CT) and magnetic resonance imaging (MRI), are suitable to show the alterations induced by this parasite on live Crassostrea gigas and Ostrea edulis oyster broodstocks. A CT scan is also able to identify small lesions in the shell during the first stage of infection. MRI allows for the visualization of the advanced status of the lesions when blisters occupy the inner surface of the shell and can impact the health status and the economic value of the mollusk. Both techniques resulted in satisfactory spatial resolution, and no motion artifacts were reported, thus enabling the authors to faithfully visualize in vivo the damage caused by the parasite. [ABSTRACT FROM AUTHOR]

This paper presents evidence that fossil Crassostrea oysters experienced much greater longevity than their modern-day descendants. For extant animals, multiple studies have revealed a positive correlation between longevity and adult body size: the larger the organism's size as an adult, the longer its lifespan. Studies have also demonstrated that organisms that take longer to reach skeletal and/or sexual maturity also tend to have longer lifespans. Fossil Crassostrea oysters are generally larger than their modern-day counterparts, and ontogenetic growth curves suggest longer lifespans and generally longer growth intervals. This evidence should be of great interest to Biblical creationists in light of the Bible's claim that humans in the pre-Flood and immediate post-Flood worlds experienced much greater longevities than modern-day humans. Animals may also have once experienced greater past longevity, since whatever genetic or environmental factors were enabling extreme human longevity were likely also operating across the animal kingdom. [ABSTRACT FROM AUTHOR]

The current study investigated the effects of heat treatment (85 °C or 100 °C for 5–20 min) on human norovirus (HuNoV) GII.4's capsid stability in fresh oysters. In addition, propidium monoazide (PMA) was used in viral samples to distinguish infectious viruses and evaluated using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR). Further, we explored the effect of the heat treatment on oyster quality (Hunter color and hardness). The titer of HuNoV for oysters significantly (p < 0.05) decreased to 0.39–1.32 and 0.93–2.27 log10 copy number/μL in the non-PMA and PMA-treated groups, respectively, after heat treatment. HuNoV in oysters not treated with PMA showed a decrease of <1.5 − log10, whereas in PMA-treated oysters, a decrease of >1 − log10 was observed after treatment at 85 °C for 10 min. Treatments for both 15 min and 20 min at 100 °C showed a >99% log10 reduction using PMA/RT-qPCR. In the Hunter color, an increase in heat temperature and duration was associated with a significant decrease in 'L' (brightness+, darkness−) and an increase in 'a' (redness+, greenness−) and 'b' (yellowness+, blueness−) (p < 0.05). Our findings confirmed that the hardness of oyster meat significantly increased with increasing temperature and time (p < 0.05). This study demonstrated that PMA/RT-qPCR was effective in distinguishing HuNoV viability in heat-treated oysters. The optimal heat treatment for oysters was 10 min at 85 °C and 5 min at 100 °C. [ABSTRACT FROM AUTHOR]

The Wildlife Services—National Wildlife Research Center Mississippi Field Station, working in conjunction with Mississippi State University, conducted a study to evaluate the effectiveness of several non-lethal, commercial, physical bird deterrents. Deterrents were available on the open market to reduce double-crested cormorant (Nannopterum auritus) (DCCO) roosting time on floating oyster cages. We hypothesized that reducing bird loafing time on floating oyster cages would reduce the potential for bird defecation. Double-crested cormorant defecation can increase coliform counts in both the water and oysters, which could result in oyster farm closure. Shellfish farms often differ from one another due to environmental factors and farm locations. Six deterrent devices were selected as options for farmers, and the amount of time DCCOs occupied floats with deterrents was compared to the time they occupied those without deterrents (i.e., on a control pond). All deterrents except the Scarem Kite significantly reduced or halted DCCO use of floats compared to the control. Of note, the Scarem Kite is the only deterrent that requires consistent wind to operate effectively. The research facility is open-air, but we did not have sufficient wind for proper Scarem Kite function. Thus, it is possible that all deterrents would have produced significant reductions in DCCO use. Our results are encouraging and show that minimal deterrent applications to oyster cage floats can help farms achieve their operational plans' goals and reduce the potential for pathogen transfer by birds. The data presented here should be considered a starting point for developing an efficient deterrent plan that meets state and federal standards. [ABSTRACT FROM AUTHOR]

High mortalities and highly variable results during the subsequent development of post-thaw larvae have been widely considered as key issues restricting the application of cryopreservation techniques to support genetic improvement programs and hatchery production in farmed marine bivalve species. To date, few studies have been undertaken to investigate the effects of cryodamage at the molecular level in bivalves. This study is the first to evaluate the effect of larval cryopreservation on the epigenetics of the resultant progenies of the Pacific oyster Crassostrea gigas. The results show that the level of DNA methylation was significantly (p < 0.05) higher and lower than that of the control when the trochophore larvae were revived and when they developed to D-stage larvae (day 1 post-fertilization), respectively, but the level returned to the control level from day 8 post-fertilization onwards. The expression of the epigenetic regulator genes DNMT3b, MeCP2, JmjCA, KDM2 and OSA changed significantly (p < 0.05) when the trochophore larvae were thawed, and then they reverted to the control levels at the D- and later larval developmental stages. However, the expression of other epigenetic regulator genes, namely, MBD2, DNMT1, CXXC1 and JmjD6, did not change at any post-thaw larval developmental stage. For the newly thawed trochophore larvae, the amount of methylated H3K4Me1 and H3K27Me1 significantly changed, and the expression of all Jumonji orthologs, except that of Jumonji5, significantly (p < 0.05) decreased. These epigenetic results agree with the data collected on larval performances (e.g., survival rate), suggesting that the effect period of the published cryopreservation technique on post-thaw larvae is short in C. gigas. [ABSTRACT FROM AUTHOR]

Oysters have the potential to be a part of more sustainable farming systems, such as multitrophic systems integrated into biofloc systems, due to their filtration activity, which enables them to act as organic consumers. However, the stress experienced by animals in a system with a high organic load can compromise their productive performance. The objective of this study was to evaluate the biological responses of Crassostrea gasar oysters when exposed to different concentrations of total suspended solids in biofloc systems. The oysters were exposed to four different concentrations of solids for 28 days. Hall effect sensors were installed on the outside of the shells to detect the movement of the oyster valves. Also, biochemical and histological analyses were conducted to assess the biological responses of the oysters to exposure to varying levels of solids. A difference in valve opening detected by the Hall sensors was observed from the second week of culture, indicating a relationship between shell closure and higher concentrations of suspended solids present in the system. In terms of biochemical analysis, a significant increase in lipid damage was observed in treatments with medium and high levels of total suspended solids compared with the control group. Conversely, no changes were observed in the gill structure of the oysters caused by the concentrations of suspended solids in the system when compared with the control. According to the analyses of gill activity and biochemistry, it is suggested that C. gasar should be cultured with total suspended solids at less than 200 mg/L. Oysters cultivated in a biofloc system keep their shells closed when subjected to high concentrations of total suspended solids; concentrations of total suspended solids below 200 mg/L do not induce oxidative stress, changes in behavior or histological alterations in C. gasar oysters cultivated in a biofloc system. [ABSTRACT FROM AUTHOR]

β-Galactosidases (EC 3.2.1.23) are exoglycosidases that catalyze the cleavage of glycoconjugates with terminal β-D-galactose residues in β1,3-, β1,4- or β1,6-linkage. Although this family of exoglycosidases has been extensively studied in vertebrates, plants, yeast, and bacteria, little information is available for mollusks. Mollusks are a diverse and highly successful group of animals that play many different roles in their ecosystems, including filter feeders and detritivores. Here, the first β-galactosidase from the Pacific oyster, Crassostrea gigas was discovered, biochemically characterized, and compared to our previously characterized slug enzyme from Arion vulgaris (UniProt Ref. Nr.: A0A0B7AQJ9). Overall, the mussel enzyme showed similar biochemical parameters to the snail enzyme. The enzyme from C. gigas was most active in an acidic environment (pH 3.5) and at a reaction temperature of 50 °C. Optimal storage conditions were up to 37 °C. In contrast to the enzyme from A. vulgaris, the supplementation of cations (Ni2+, Co2+, Mn2+, Mg2+, Ca2+, Cu2+, Ba2+) increased the activity of the enzyme from C. gigas. Substrate specificity studies of the β-galactosidases from the mussel, C. gigas, and the slug, A. vulgaris, revealed activity towards terminal β1,3- and β1,4-linked galactose residues for both enzymes. Using the same substrates in labeled and unlabeled form, we were able to detect the effect of labeling on the β-galactosidase activity using MALDI-TOF MS, HPTLC, and HPLC. While lactose was cleaved by the enzymes in an unlabeled or labeled state, galacto-N-biose was not cleaved as soon as a 2-amino benzoic acid label was added. In this study we present the biochemical characterization of the first recombinantly expressed β-galactosidase from the Pacific oyster, C. gigas, and we compare different analytical methods for the determination of β-galactosidase activity using the enzyme from C. gigas and A. vulgaris. [ABSTRACT FROM AUTHOR]

Parallel diversification provides a proper framework for studying the role of natural selection in evolution. Yet, empirical studies from ecological 'non‐model' species of invertebrates are limited at the whole genome level. Here, we presented a chromosome‐scale genome assembly for Crassostrea angulata and investigated the parallel genomic evolution in oysters. Specifically, we used population genomics approaches to compare two southern–northern oyster species pairs (C. angulata–C. gigas and southern–northern C. ariakensis) along the coast of China. The estimated divergence time of C. angulata and C. gigas is earlier than that of southern and northern C. ariakensis, which aligns with the overall elevated genome‐wide divergence. However, the southern–northern C. ariakensis FST profile represented more extremely divergent "islands". Combined with recent reciprocal hybridization studies, we proposed that they are currently at an early stage of speciation. These two southern–northern oyster species pairs exhibited significant repeatability in patterns of genome‐wide differentiation, especially in genomic regions with extremely high and low divergence. This suggested that divergent and purifying selection has contributed to the genomic parallelism between southern and northern latitudes. Top differentiated genomic regions shared in these two oyster species pairs contained candidate genes enriched for functions in energy metabolism, especially adipogenesis, which are closely related to reproductive behaviours. These genes might be good candidates for further investigation in vivo. In conclusion, our results suggest that similar divergent selection and shared genomic features could predictably transform standing genetic variation within one species pair into differences in another. [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]

The evaluation of oyster marinating (Crassostrea gasar) and pasteurization process in vacuum packaging during storage. The aim of this study was to establish better conditions for marinating and pasteurization for oysters (Crassostrea gasar) and to evaluate their shelf life. Microbiological, physicochemical and sensory analyzes were carried out on the oysters and on the optimized product. In the vacuum-packed product, under refrigeration, pH, water activity (aw), total volatile bases (N-TVB) and texture analyzes were performed, every 7 days for 35 days. Oysters had a high protein, mineral and amino acid content and a low lipid content. Planning 23 and 221 hour, 2.5% acetic acid, 1% NaCl and pasteurization was 62°C/2 min. Sensory analysis achieved acceptability above 80%. Marinated oysters remained suitable for consumption for 21 days, being an alternative to extend the shelf life and add value. [ABSTRACT FROM AUTHOR]

The regeneration of bone defects is a major challenge for clinical orthopaedics. Herein, we designed and prepared a new type of bioactive material, using stingray skin collagen and oyster shell powder (OSP) as raw materials. A stingray skin collagen/oyster osteoinductive composite scaffold (Col-OSP) was prepared for the first time by genipin cross-linking, pore-forming and freeze-drying methods. These scaffolds were characterized by ATR-FTIR, SEM, compression, swelling, cell proliferation, cell adhesion, alkaline phosphatase activity, alizarin red staining and RT-PCR etc. The Col-OSP scaffold had an interconnected three-dimensional porous structure, and the mechanical properties of the Col-OSP composite scaffold were enhanced compared with Col, combining with the appropriate swelling rate and degradation rate, the scaffold was more in line with the requirements of bone tissue engineering scaffolds. The Col-OSP scaffold was non-toxic, promoted the proliferation, adhesion, and differentiation of MC3T3-E1 cells, and stimulated the osteogenesis-related genes expressions of osteocalcin (OCN), collagen type I (COL-I) and RUNX2 of MC3T3-E1 cells. [ABSTRACT FROM AUTHOR]

Predator–prey interactions are a key feature of ecosystems and often chemically mediated, whereby individuals detect molecules in their environment that inform whether they should attack or defend. These molecules are largely unidentified, and their discovery is important for determining their ecological role in complex trophic systems. Homarine and trigonelline are two previously identified blue crab (Callinectes sapidus) urinary metabolites that cause mud crabs (Panopeus herbstii) to seek refuge, but it was unknown whether these molecules influence other species within this oyster reef system. In the current study, homarine, trigonelline, and blue crab urine were tested on juvenile oysters (Crassostrea virginica) to ascertain if the same molecules known to alter mud crab behavior also affect juvenile oyster morphology, thus mediating interactions between a generalist predator, a mesopredator, and a basal prey species. Oyster juveniles strengthened their shells in response to blue crab urine and when exposed to homarine and trigonelline in combination, especially at higher concentrations. This study builds upon previous work to pinpoint specific molecules from a generalist predator's urine that induce defensive responses in two marine prey from different taxa and trophic levels, supporting the hypothesis that common fear molecules exist in ecological systems. [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]

Recently, three proton channels (HV) have been identified and characterized in Aplysia californica (AcHV1‐3). Focusing on AcHV1 and AcHV2, analysis of Transcriptome Shotgun Assembly and genomic databases of 91 molluscs identified HV homologous channels in other molluscs: channels homologous to AcHV1 and to AcHV2 were found in 90 species (56 full‐length sequences) and in 33 species (18 full‐length sequences), respectively. Here, we report the discovery of a fourth distinct proton channel family, HV4. This new family has high homology to AcHV1 and AcHV2 and was identified only in bivalvian molluscs (13 species, 12 full‐length sequences). Typically, these channels possess an extracellular S1–S2 loop of intermediate size (~ 20 amino acids) compared to the shorter loops of molluscan HV1 channels (~ 13 amino acids) and the much larger loops of molluscan HV2 channels (> 65 amino acids). The characteristic voltage‐sensor motif in S4 possesses only two arginine residues with the common third arginine being replaced by a lysine. Moreover, HV4 channels are much smaller with only around 200 amino acids in total length. The smallest functional channel found so far in nature (189 amino acids) is expressed in the pacific oyster Crassostrea gigas (CgHV4) and might be considered an archetypical minimal proton channel. Functional expression and electrophysiological characterization demonstrated that CgHV4 shares distinctive hallmarks of other investigated proton channels as high proton selectivity, slow activation, and pH‐ and voltage‐regulated gating. This work is the first description of a HV4 type channel, adding a new member to the recently expanded family of proton channels. [ABSTRACT FROM AUTHOR]

Chama coralloides Reeve, 1846 is a commercially important mollusk in Acapulco, Mexico. There is currently no fisheries regulation or protection. Therefore, the objective of the present work was to estimate the growth parameters of C. coralloides using the Schnute model cases. Shell length data collected from March 2019 to December 2021 were used. A multinomial analysis was performed to determine the modal groups monthly. Using the mean lengths of each modal group, a modal progression was performed to define the time increments ∆t, which were taken as equivalent representations of the data from direct age estimation methods (mark-recapture). These data were used to estimate the individual growth parameters using the five cases of the Schnute model and to define the case that best describes the growth. 2804 organisms were analyzed, with lengths ranging from 7.61 to 116.30 mm SL. Multinomial analysis showed one to four modal groups per month and 14 cohorts were identified. The best-fit case was case 5 (wi = 0.72) with an L∞ = 114.2 mm, followed by case 1 (wi = 0.28) with an L∞= 109.8 mm. Both cases (5 and 1) were modeled and because the best model did not reach 90%, a mean model was estimated. C. coralloides presented a type of asymptotic growth, with an estimated L∞ that can be reached nearly 22 years. [ABSTRACT FROM AUTHOR]

Simple Summary: Invasive species (IS) can upset both aquatic and terrestrial ecosystems which, in turn, can negatively affect production and economic development. Thus, many countries understand the importance of performing risk assessments on the potential for species to invade an ecosystem. Here, we report on our development of a quantitative risk assessment model to estimate the introduction of invasive aquatic animals into China's inland waters. This model is based on the analytic hierarchy process (AHP). We propose that the use of this model can provide the basis to better understand the ecological impact of invasive aquatic animals and also effective protocols for risk management should an invasion take place. The spread of invasive species (IS) has the potential to upset ecosystem balances. In extreme cases, this can hinder economical utilization of both aquatic (fisheries) and terrestrial (agricultural) systems. As a result, many countries regard risk assessment of IS as an important process for solving the problem of biological invasion. Yet, some IS are purposefully introduced for what is seen as their potential economic benefits. Thus, conducting IS risk assessments and then formulating policies based on scientific information will allow protocols to be developed that can reduce problems associated with IS incursions, whether occurring purposefully or not. However, the risk assessment methods currently adopted by most countries use qualitative or semiquantitative methodologies. Currently, there is a mismatch between qualitative and quantitative assessments. Moreover, most assessment systems are for terrestrial animals. What is needed is an assessment system for aquatic animals; however, those currently available are relatively rudimentary. To fill this gap, we used the analytic hierarchy process (AHP) to build a risk assessment model system for aquatic IS. Our AHP has four primary indexes, twelve secondary indexes, and sixty tertiary indexes. We used this AHP to conduct quantitative risk assessments on five aquatic animals that are typically introduced in China, which have distinct biological characteristics, specific introduction purposes, and can represent different types of aquatic animals. The assessment results show that the risk grade for Pterygoplichthys pardalis is high; the risk grade for Macrobrachium rosenbergii, Crassostrea gigas, and Trachemys scripta elegans is medium; and the grade risk for Ambystoma mexicanum is low. Risk assessment of the introduction of aquatic animals using our AHP is effective, and it provides support for the introduction and healthy breeding of aquatic animals. Thus, the AHP model can provide a basis for decision-making risk management concerning the introduction of species. [ABSTRACT FROM AUTHOR]

Simple Summary: Transoceanic shipping and global development of aquaculture are the main vectors for the introduction of marine organisms, as adults or their larvae, to new remote locations. Recent invasions by large species may be well known and documented, while older and smaller-bodied invasions are often hidden and more difficult to detect. In the present study, we investigated, using molecular methods, marine worms that bore into the shells of commercial molluscs on four continents. We have identified them as Polydora hoplura, a species originally described from Italy. The highest genetic diversity was detected in South African population. While high genetic diversity is often regarded as indicative of a species' natural range, our analysis of the worldwide discovery of P. hoplura calls into question its natural distribution in South Africa. The high genetic diversity of P. hoplura in this region may be the result of a complex dispersal history by ships and aquaculture. We tentatively propose the Northwest Pacific, or at the most the Indo–West Pacific, as its home region, not the Atlantic Ocean or the Eastern Pacific Ocean, and call for further exploration of this hypothesis. The spionid polychaete Polydora hoplura Claparède, 1868 is a shell borer widely occurring across the world and considered introduced in many areas. It was originally described in the Gulf of Naples, Italy. Adult diagnostic features are the palps with black bands, prostomium weakly incised anteriorly, caruncle extending to the end of chaetiger 3, short occipital antenna, and heavy sickle-shaped spines in the posterior notopodia. The Bayesian inference analysis of sequence data of four gene fragments (2369 bp in total) of the mitochondrial 16S rDNA, nuclear 18S, 28S rDNA and Histone 3 has shown that worms with these morphological features from the Mediterranean, northern Europe, Brazil, South Africa, Australia, Republic of Korea, Japan and California are genetically identical, form a well-supported clade, and can be considered conspecific. The genetic analysis of a 16S dataset detected 15 haplotypes of this species, 10 of which occur only in South Africa. Despite the high genetic diversity of P. hoplura in South Africa, we tentatively propose the Northwest Pacific, or at the most the Indo–West Pacific, as its home region, not the Atlantic Ocean or the Eastern Pacific Ocean. The history of the discovery of P. hoplura around the world appears to be intimately linked to global shipping commencing in the mid-19th century, followed by the advent of the global movement of commercial shellfish (especially the Pacific oyster Magallana gigas) in the 20th century, interlaced with continued, complex dispersal by vessels and aquaculture. Given that P. hoplura has been detected in only a few of the 17 countries where Pacific oysters have been established, we predict that it may already be present in many more regions. As global connectivity through world trade continues to increase, it is likely that novel populations of P. hoplura will continue to emerge. [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]

The oyster Saccostrea cucullata (a native oyster of the Persian Gulf) is one of the most valuable edible species that is currently a candidate for cultivation for export. Anyway, there is no detailed information about its reproduction pattern in the Persian Gulf. The present study assessed the annual reproductive cycle of S. cucullata along the rocky coasts of Bushehr, Iran (the north of the Persian Gulf). In this regard, the gametogenesis of S. cucullata was evaluated monthly based on the gonad histology and steroid analysis during January 2021 to April 2022. Water temperature changes had a close relation with the reproductive cycle. Most of the females and males were in inactive or sexually rest stages during November and December (19–20 ℃). Gametogenic activity in male and female S. cucullata started by mid-February (20 ℃). The ripe oysters mainly were observed from May to July and to some extent during August and September when the temperature was more than 30 °C. More than 85% of oysters collected in September and October were partially or completely spawned. In conclusion, S. cucullata spawns more or less throughout the year, although its spawning peak in the Bushehr coasts is from June to August. [ABSTRACT FROM AUTHOR]

The Pacific oyster Crassostrea gigas is a mollusc with calcium carbonate shell, while the brachiopod Lingula anatina is with calcium phosphate biominerals. Here, we compared ultrastructure observations of the marginal region and the central region of mantles between C. gigas and L. anatina using histology and transmission electron microscopy (TEM) approaches. Our results found both species have similar cell types including the columnar epidermis cell, electron-dense granules cell and electron-transparent granules cell. However, the ultrastructure of the columnar epidermal subtype cells and the inclusion contents of secretory cells in those two species were different. The columnar epidermal cells of C. gigas consists of subtype A that mainly concentrated on the marginal region of mantle, subtype B mainly concentrated on the central region of mantle and subtype C was not common. The sizes of those cells were 7-15 μm. Meanwhile, columnar epidermal cells of L. anatina consist of subtypes A', B' and C'. Their sizes are 10-15 μm. As for secretory cells, both species had electron-dense granules cell and electron-transparent granules cell. However, L. anatina also contained a special class of secretory cells containing lamellar bodies. Those results can partially explain the difference of shell composition between brachiopods and mollusc, and provide reference for the study of shell formation mechanism and mineralization of brachiopods and mollusc. [ABSTRACT FROM AUTHOR]

In this paper, an LC-MS/MS method for the simultaneous identification and quantification of cyanotoxins with hydrophilic and lipophilic properties in edible bivalves is presented. The method includes 17 cyanotoxins comprising 13 microcystins (MCs), nodularin (NOD), anatoxin-a (ATX-a), homoanatoxin (h-ATX) and cylindrospermopsin (CYN). A benefit to the presented method is the possibility for the MS detection of MC-LR-[Dha7] and MC-LR-[Asp3] as separately identified and MS-resolved MRM signals, two congeners which were earlier detected together. The performance of the method was evaluated by in-house validation using spiked mussel samples in the quantification range of 3.12–200 µg/kg. The method was found to be linear over the full calibration range for all included cyanotoxins except CYN for which a quadratic regression was used. The method showed limitations for MC-LF (R2 = 0.94), MC-LA (R2 ≤ 0.98) and MC-LW (R2 ≤ 0.98). The recoveries for ATX-a, h-ATX, CYN, NOD, MC-LF and MC-LW were lower than desired (<70%), but stable. Despite the given limitations, the validation results showed that the method was specific and robust for the investigated parameters. The results demonstrate the suitability of the method to be applied as a reliable monitoring tool for the presented group of cyanotoxins, as well as highlight the compromises that need to be included if multi-toxin methods are to be used for the analysis of cyanotoxins with a broader range of chemical properties. Furthermore, the method was used to analyze 13 samples of mussels (Mytilus edulis) and oysters (Magallana gigas) collected in the 2020–2022 summers along the coast of Bohuslän (Sweden). A complementary qualitative analysis for the presence of cyanotoxins in phytoplankton samples collected from marine waters around southern Sweden was performed with the method. Nodularin was identified in all samples and quantified in bivalve samples in the range of 7–397 µg/kg. Toxins produced by cyanobacteria are not included in the European Union regulatory monitoring of bivalves; thus, the results presented in this study can be useful in providing the basis for future work including cyanotoxins within the frame of regulatory monitoring to increase seafood safety. [ABSTRACT FROM AUTHOR]