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With the projected escalation of extreme storm events, coastal ecosystems risk undergoing catastrophic shifts and losing essential ecosystem services. Subtidal soft‐bottom mussel beds, vital components of these ecosystems, are particularly vulnerable to hydrodynamically‐induced dislodgement (i.e., detachment of mussel clumps from the bed), especially during storms. However, the mechanisms underlying the resilience—comprising both resistance and recovery—of these beds to storms remain unclear, despite being essential for informed management.This study addresses this knowledge gap regarding subtidal soft‐bottom mussel beds by: (i) quantifying their dislodgement threshold (i.e., the hydrodynamics causing widespread dislodgement of mussel clumps) using novel in situ monitoring methodologies in a representative region, namely the Dutch Wadden Sea; (ii) unveiling the influence of prior life history (here, wave exposure extent) and storm durations on their dislodgement thresholds through a flume study; and (iii) assessing the impacts of repeated storms and prior life histories (here, wave exposure extent and substrate types) on their recovery (i.e. mussel re‐aggregation) through mesocosm experiments.Integrated experimental evidence indicates that: (i) hydrodynamic‐induced dislodgement is a sudden process characterized by distinct near‐bed orbital velocity thresholds, which were identified at our study site to be between 0.45 and 0.50 m s−1; (ii) peak storm intensity, rather than storm duration, primarily drives the dislodgement of subtidal soft‐bottom mussel beds, and prior wave exposure extent regulates the dislodgement threshold; (iii) repeated storms do not seem to affect the recovery of these beds following storm‐related disturbances when the conditions between storms are conducive to mussel re‐aggregation, whereas substrate type significantly impacts recovery.Synthesis and applications. Overall, concerns regarding subtidal soft‐bottom mussel beds degradation primarily stem from increasing storm intensity and their limited resistance to such events. The methodology we developed enables low‐cost quantification of mussel resistance thresholds across broad spatiotemporal scales, facilitating the pinpointing of vulnerable areas. Our findings inform strategic management by highlighting the influential role of prior life histories in shaping mussel bed resistance and the potential to accelerate mussel bed recovery through substrate modification (e.g., shell additions). Both our methodology and findings hold promise for application in comparable ecosystems, such as oyster and coral reefs. [ABSTRACT FROM AUTHOR]

Urbanization is particularly prevalent along the coast, causing a considerable change in the ecology of the habitats found there. Ports, docks and all the structures linked to this anthropization modify the coastal environment by providing new niches, but also new constraints. Thus, ports are ecosystems in their own right, although they are rarely studied as such. In Europe's largest marina (La Rochelle, France), among the multitude of organisms inhabiting it, four taxa seem particularly interesting to study: Mytilidae, Ostreïdae, Pectinidae and ascidiacea. Because these taxa, which belong to the bivalve and tunicate groups, are the stewards of the health of the port environment both as bioindicators and as engineering species. The establishment of a systematic and regular census allows us to study the evolution of their populations and to determine what influences their distribution. To have as less impact as possible on the fauna studied, the census was carried out by underwater photography. The study shows that the populations are partly conditioned by the hydrodynamics of the environment and by the anthropic activity which is carried out there. Indeed, this study, which was carried out in a particular context (before and after the COVID-19 health crisis), shows the importance of anthropic pressure, particularly on the bivalve communities. A large amount of data is needed to understand what precisely governs bivalve and tunicate populations. Therefore, an innovative method, using artificial intelligence to automate the analyses, was tested in this study. This promising method should facilitate the census by reducing the analysis time. [ABSTRACT FROM AUTHOR]

Global declines in marine shellfish have resulted in widespread efforts to restore populations. Previous research has predominantly focused on substrate‐limited rather than recruitment‐limited systems, yet given increased use of aquaculture‐produced stock to restore marine bivalves, there is a need to understand differences in the survival of hatchery‐produced and translocated wild stock. We conducted a systematic review and synthesis of studies that quantified the survival of outplanted marine bivalves. The systematic review identified 893 unique stocking events across 111 studies for 29 species across 10 families. Most research has occurred in temperate regions (73%), across four bivalve families (Ostreidae 37%, Pectinidae 20%, Veneridae 16% and Mytilidae 11%). More stockings have outplanted hatchery‐produced (66%) than translocated stock (34%). We conducted quantitative analyses for five species to determine how stock origin, size at outplant, outplant density, substrate co‐deployment, predator exclusion and time since outplant influences survival. Survival consistently decreased through time across all species. Substrate co‐deployment, stock origin and size at outplant did not influence survival, while predator exclusion and outplant density affected some species. Synthesis and applications. Our analyses broadly demonstrate variability in the survival of outplanted bivalves through time, however predicted survival was poor after 2 years (<3%). Generally low survival highlights difficulties associated with conducting scalable restoration in recruitment‐limited systems. Based on our findings, using hatchery‐produced stock, mitigating predation and outplanting epifaunal bivalves at high densities may increase survival probabilities when outplanting stock for restoration. Further exploration is needed to understand whether use of aquaculture‐produced stock results in similar ecosystem structure, function, and service provisioning to natural and restored shellfish reefs in recruitment‐limited systems. [ABSTRACT FROM AUTHOR]

The porous core of the marine mussel provides mechanical advantages of achieving substantial deformation and high toughness. Inspired by the unique mechanical behaviours of mussel plaque cores, the present study develops ultra-soft, stretchable and tough cellular solids by bio-mimicking their porosity and properties. Although scaling laws to correlate the mechanical properties of cellular solids with bulk materials have been established, they are primarily based on experimental data from stiff cellular solids. In this article, the scaling law for soft cellular solids is studied to relate tensile properties and toughness with volume fractions. Unlike conventional stiff cellular solids, the scaling law shows that soft lattices experience bending-dominated deformation at the elastic state and fail under stretching-dominated deformation. Uniaxial and planar tensile tests demonstrate that the proposed soft lattices achieved Young's modulus of 0.04∼0.17 MPa, failure strain of 135.5∼213.9% and toughness of 582∼941 J m−2 by manipulating the volume fraction (0.2∼0.5), positioning them as softer, more stretchable and tougher than the majority of engineering foams in the Ashby diagram. In addition, the toughness of soft lattices is found to be sensitive to volume fraction but insensitive to initial crack length, thickness and height (≥20mm). Two distinct failure modes, truss failure and joint failure, are correlated with volume fraction. The soft lattice with a volume fraction (around 0.4) similar to mussel plaque fails at the transition of these two failure modes and achieves the highest toughness. This study contributes new insights to the materials science community and lays the foundation for the development of lightweight, damage-tolerant and high-performance metamaterials. [ABSTRACT FROM AUTHOR]

Lubricant‐infused slippery surfaces have recently emerged as promising antifouling coatings, showing potential against proteins, cells, and marine mussels. However, a comprehensive understanding of the molecular binding behaviors and interaction strength of foulants to these surfaces is lacking. In this work, mussel‐inspired chemistry based on catechol‐containing chemicals including 3,4‐dihydroxyphenylalanine (DOPA) and polydopamine (PDA) is employed to investigate the antifouling performance and repellence mechanisms of fluorinated‐based slippery surface, and the correlated interaction mechanisms are probed using atomic force microscopy (AFM). Intermolecular force measurements and deposition experiments between PDA and the surface reveal the ability of lubricant film to inhibit the contact of PDA particles with the substrate. Moreover, the binding mechanisms and bond dissociation energy between a single DOPA moiety and the lubricant‐infused slippery surface are quantitatively investigated employing single‐molecule force spectroscopy based on AFM (SM‐AFM), which reveal that the infused lubricant layer can remarkably influence the dissociation forces and weaken the binding strength between DOPA and underneath per‐fluorinated monolayer surface. This work provides new nanomechanical insights into the fundamental antifouling mechanisms of the lubricant‐infused slippery surfaces against mussel‐derived adhesive chemicals, with important implications for the design of lubricant‐infused materials and other novel antifouling platforms for various bioengineering and engineering applications. [ABSTRACT FROM AUTHOR]

The natural populations of the marine mussel Mytilus chilensis and the associated aquaculture industry forms a sensitive social-ecological system that relies on the released propagules for cultivation in the highly heterogeneous environment (temperature, productivity, and salinity) of northern Patagonia (42–44 °S). We assessed spatial genetic structure, signals of local adaptation, and population assignment of M. chilensis analyzing 5963 SNPs from 125 individuals across six natural populations sampled over two consecutive years along the southeast Pacific coast (39° 25′ to 43° 07′ S, ~ 430 km). Neutral and putatively adaptive loci revealed high genetic diversity and low genetic differentiation among populations. Of the whole dataset, less than 1% (50) of loci were identified as putatively adaptive through multiple approaches, with only 0.1% detected in by all of them, and only two loci of them were correlated with environmental variables. No evidence of Isolation by Environment (IBE) was found, albeit a slight differentiation in the southern sampling location (Yaldad). These results suggest that the genetic structure observed is primarily shaped by neutral processes with weak signals of local adaptation. Gene-flow appears to be the main evolutionary force influencing the species' population genetic structure. Because of the importance for the industry, the probability of correct assignment of individuals to their population of origin using allelic frequencies was evaluated. Analyses exhibited relatively low probabilities (< 50% for four out of six sites) of accurately assigning individuals to their geographic origin, with a limited success of SNP markers the for such purposes. Likely, species' high dispersal capacity, seed translocation, and the spill-over effect of mussel aquaculture prevents population genetic differentiation through high effective gene flow, hindering local genetic adaptation. [ABSTRACT FROM AUTHOR]

For polyacrylate latex pressure-sensitive adhesives (PSAs), high peel strength is of crucial significance. It is not only a key factor for ensuring the long-lasting and effective adhesive force of polyacrylate latex PSAs but also can significantly expand their application scope in many vital fields, such as packaging, electronics, and medical high-performance composite materials. High peel strength can guarantee that the products maintain stable and reliable adhesive performance under complex and variable environmental conditions. However, at present, the peel strength capacity of polyacrylate latex PSAs is conspicuously insufficient, making it difficult to fully meet the urgent market demand for high peel strength, and severely restricting their application in many cutting-edge fields. Therefore, based on previous experimental studies, and deeply inspired by the adhesion mechanism of natural marine mussels, in this study, a traditional polyacrylate latex PSA was ingeniously graft-modified with 3,4-dihydroxybenzaldehyde (DHBA) through the method of monomer-starved seeded semi-continuous emulsion polymerization, successfully synthesizing novel high-peel-strength polyacrylate latex pressure-sensitive adhesives (HPSAs) with outstanding strong adhesion properties, and the influence of DHBA content on the properties of the HPSAs was comprehensively studied. The research results indicated that the properties of the modified HPSAs were comprehensively enhanced. Regarding the water resistance of the adhesive film, the minimum water absorption rate was 4.33%. In terms of the heat resistance of the adhesive tape, it could withstand heat at 90 °C for 1 h without leaving residue upon tape peeling. Notably, the adhesive properties were significantly improved, and when the DHBA content reached 4.0%, the loop tack and 180° peel strength of HPSA4 significantly increased to 5.75 N and 825.4 gf/25 mm, respectively, which were 2.5 times and 2 times those of the unmodified PSA, respectively. Such superior adhesive performance of HPSAs, on the one hand, should be attributed to the introduction of the bonding functional monomer DHBA with a rich polyphenol structure; on the other hand, the acetal structure formed by the grafting reaction of DHBA with the PSA effectively enhanced the spatial network and crosslink density of the HPSAs. In summary, in this study, the natural biological adhesion phenomenon was ingeniously utilized to increase the peel strength of pressure-sensitive adhesives, providing a highly forward-looking and feasible direct strategy for the development of environmentally friendly polyacrylate latex pressure-sensitive adhesives. [ABSTRACT FROM AUTHOR]

Plastic pollution of marine environments has become a global problem. Microplastics have the potential to bioaccumulate in marine biota and ecosystems. Depending on their bioavailability and size, they can be potentially dangerous to the health of organisms and ecosystems. This study aimed to assess microplastics bioaccumulation in bivalve species from the hypereutrophic Varna Lake. Totally, 58 bivalves of three species (Mya arenaria, Mytilus galloprovincialis and Cerastroderma glaucum) were collected from Varna Lake. The most common type of microplastics were fragments (61.54%) followed by fibres (15.38%), microbeads (11.54%), films and sponge/foam. Microplastics were recovered in 60 % of M. galloprovincialis (1.73±2.09 part/ind.), 58 % of M. arenaria (1.77±2.27 part/ind.), and 29 % of C. glaucum (0.35±0.61 part/ind.). The lowest number of microplastics was identified in C. glaucum (0-2 part/ind.) while M. galloprovincialis (0-6 part/ind.) and M. arenaria (0-8 part/ind.) presented almost equal content. The most frequent plastic colour was blue (26.92 %) followed by red (25.64 %), grey (15.38 %), black (12.82 %) and green (10.26 %). Our study reveals the first evaluation of the uptake, level of accumulation, shape, colour and size class of microplastics by three native bivalve species in Varna Lake. Much more research is needed for a more precise assessment of the patterns of bioaccumulation and the effects of microplastics in marine bivalves. [ABSTRACT FROM AUTHOR]

Microeukaryotes are a diverse and often overlooked group of microbes that are important in food webs and other ecological linkages. Little is known about microeukaryotes associated with aquatic invertebrates, although filter feeders such as mussels are likely to take in and potentially retain microeukaryotes in their gut while feeding. Microeukaryotes such as apicomplexans have been reported in marine mussel species, but no studies have examined the presence of these microorganisms in freshwater mussels or how they relate to mussel host species or environmental conditions. In this study, microbial community DNA was extracted from the gut tissue of over 300 freshwater mussels, representing 22 species collected from rivers in the southeastern USA. Microeukaryote DNA was detected using PCR amplification, followed by the sequencing of positive amplicons. Microeukaryotes were found in 167 individual mussels (53%) of those tested. Amplicons included dinoflagellates/algae that differed between mussel species and are likely food sources that were distinct from those found in water and sediment samples analyzed concurrently. A total of 5% of the positive amplicons were non-photosynthetic alveolates that could represent parasitic microeukaryotes. Understanding the distribution of microeukaryotes in the freshwater mussel gut microbiome could further our understanding of the ongoing decline of mussel populations. [ABSTRACT FROM AUTHOR]

The impressive adhesive capacity of marine mussels has inspired various fascinating designs in biomedical fields. Mussel-inspired injectable adhesive hydrogels, as a type of promising mussel-inspired material, have attracted much attention due to their minimally invasive property and desirable functions provided by mussel-inspired components. In recent decades, various mussel-inspired injectable adhesive hydrogels have been designed and widely applied in numerous biomedical fields. The rational incorporation of mussel-inspired catechol groups endows the injectable hydrogels with the potential to exhibit many properties, including tissue adhesiveness and self-healing, antimicrobial, and antioxidant capabilities, broadening the applications of injectable hydrogels in biomedical fields. In this review, we first give a brief introduction to the adhesion mechanism of mussels and the characteristics of injectable hydrogels. Further, the typical design strategies of mussel-inspired injectable adhesive hydrogels are summarized. The methodologies for integrating catechol groups into polymers and the crosslinking methods of mussel-inspired hydrogels are discussed in this section. In addition, we systematically overview recent mussel-inspired injectable adhesive hydrogels for biomedical applications, with a focus on how the unique properties of these hydrogels benefit their applications in these fields. The challenges and perspectives of mussel-inspired injectable hydrogels are discussed in the last section. This review may provide new inspiration for the design of novel bioinspired injectable hydrogels and facilitate their application in various biomedical fields. [ABSTRACT FROM AUTHOR]

Coastal bivalves are important ecosystem engineers, and identifying critical habitats can enhance conservation outcomes for threated keystone species as well as determining hotspots for invasive species. As early action is more efficient in both conservation and mitigation of species invasions, efficient and reliable tools for mapping and monitoring species over large scales are essential. We assessed the reliability and efficiency of towed video and quadrat sampling for estimating the abundance of three keystone macrofaunal bivalve species. To assess reliability, we compared the measured density based on each of the two methods to the "true" density estimated by manually surveying an entire transect. We found that both the video and quadrat method caused underestimation of the density of bivalves, but that the amount of underestimation was comparable, and further that both methods took substantially less time than surveying an entire transect manually. The video method underestimated the abundance of Pacific oysters (Magallana gigas), European flat oysters (Ostrea edulis), and blue mussels (Mytilus spp.) by 23%, 24%, and 16%, respectively. The causes of underestimation for the two oyster species were bivalves grouped in clusters, large amounts of small individuals, and generally higher abundances. While Mytilus spp. were underestimated overall, here observer experience was important, with inexperienced observers overestimating and experienced observers underestimating. Our study found both methods to be reliable and efficient for estimating the abundance of three keystone macrofaunal species, suggesting their potential applicability to other sessile or slow‐moving species. We propose that these methods, due to their efficiency, can advance scientific knowledge and enhance conservation outcomes by establishing population baselines, assessing trends over time, and identifying and protecting critical habitats. [ABSTRACT FROM AUTHOR]

The smooth-shelled blue mussel, Mytilus edulis is part of the Mytilus species complex, encompassing at least three putative species: M. edulis, Mytilus galloprovincialis , and Mytilus trossulus. These three species occur on both sides of the Atlantic and hybridize in nature, and both M. edulis and M. galloprovincialis are important aquaculture species. They are also invasive species in many parts of the world. Here, we present a chromosome-level assembly of M. edulis. We used a combination of PacBio sequencing and Dovetail's Omni-C technology to generate an assembly with 14 long scaffolds containing 94% of the predicted length of the M. edulis genome (1.6 out of 1.7 Gb). Assembly statistics were as follows: total length = 1.65 Gb, N50 = 116 Mb, L50 = 7, and L90 = 13. BUSCO analysis showed 92.55% eukaryote BUSCOs identified. AB- Initio annotation using RNA-seq from mantle, gills, muscle, and foot predicted 47,128 genes. These gene models were combined with IsoSeq validation resulting in 45,379 full CDS protein sequences and 129,708 isoforms. Using GBS and shotgun sequencing, we also sequenced several eastern Canadian populations of Mytilus to characterize single-nucleotide as well as structural variance. This high-quality genome for M. edulis provides a platform to develop tools that can be used in breeding, molecular ecology and evolution to address questions of both commercial and environmental perspectives. [ABSTRACT FROM AUTHOR]

The global threat of antimicrobial resistance (AMR) is exacerbated by the mobilization of antimicrobial resistance genes (ARGs) occurring in different environmental niches, including seawater. Marine environments serve as reservoirs for resistant bacteria and ARGs, further complicated by the ubiquity of microplastics (MPs). MPs can adsorb pollutants and promote bacterial biofilm formation, creating conditions favorable to the dissemination of ARGs. This study explores the dynamics of ARG transfer in the marine bivalve Mytilus galloprovincialis within a seawater model, focusing on the influence of polyethylene MPs on the mobilization of the Tn916-carrying tetM gene and plasmid-encoded ermB. Experiments revealed that biofilm formation on MPs by Enterococcus faecium and Listeria monocytogenes facilitated the transfer of the tetM resistance gene, but not the ermB gene. Furthermore, the presence of MPs significantly increased the conjugation frequency of tetM within mussels, indicating that MPs enhance the potential for ARG mobilization in marine environments. These findings highlight the role of MPs and marine organisms in ARG spread, underscoring the ecological and public health implications. [ABSTRACT FROM AUTHOR]

Water molecules pose a significant obstacle to conventional adhesive materials. Nevertheless, some marine organisms can secrete bioadhesives with remarkable adhesion properties. For instance, mussels resist sea waves using byssal threads, sandcastle worms secrete sandcastle glue to construct shelters, and barnacles adhere to various surfaces using their barnacle cement. This work initially elucidates the process of underwater adhesion and the microstructure of bioadhesives in these three exemplary marine organisms. The formation of bioadhesive microstructures is intimately related to the aquatic environment. Subsequently, the adhesion mechanisms employed by mussel byssal threads, sandcastle glue, and barnacle cement are demonstrated at the molecular level. The comprehension of adhesion mechanisms has promoted various biomimetic adhesive systems: DOPA-based biomimetic adhesives inspired by the chemical composition of mussel byssal proteins; polyelectrolyte hydrogels enlightened by sandcastle glue and phase transitions; and novel biomimetic adhesives derived from the multiple interactions and nanofiber-like structures within barnacle cement. Underwater biomimetic adhesion continues to encounter multifaceted challenges despite notable advancements. Hence, this work examines the current challenges confronting underwater biomimetic adhesion in the last part, which provides novel perspectives and directions for future research. [ABSTRACT FROM AUTHOR]

Background: Mitochondrial genomes have become a powerful tool for studying molecular genetics and phylogeny of mollusks. Currently, the position of Modiolinae within Mytilidae and the taxonomic and phylogenetic relationships within Modiolinae were still controversial. This study focuses on the complete mitochondrial genomes of two species: Modiolus modulaides (Röding, 1798) and Modiolus auriculatus Krauss, 1848, which have not been sequenced before. Methods and results: We assembled and characterized the mitochondrial genomes of M. modulaides and M. auriculatus and then analyzed the phylogenetic relationships. The mitochondrial genomes of M. modulaides and M. auriculatus were 15,422 bp and 16,027 bp, respectively. Both of them were composed of 36 functional genes, including 12 protein-coding genes, 22 transfer RNAs, and 2 ribosomal RNAs. All protein-coding genes showed A + T bias, positive GC skews, and negative AT skews in nucleotide composition. Phylogenetic analysis based on the mitochondrial genomes showed that Modiolinae and Bathymodiolinae clustered together to form a sister relationship. Seven Modiolinae species were divided into two clades: L1 (M. modulaides, M. auriculatus and Modiolus philippinarum Hanley, 1843) and L2 [Modiolus modiolus (Linnaeus, 1758), Modiolus kurilensis Bernard, 1983, Modiolus nipponicus (Oyama, 1950), and Modiolus comptus (Sowerby III, 1915)]. The divergence time of the two clades was approximately 105.75 Ma. Furthermore, the transfer RNA gene rearrangement, longer genetic distance, and greater genetic differentiation were confirmed between the L1 and L2 clades, as well as differences in the external characteristics of the shells of the two clades. Conclusions: Based on the molecular data, it was speculated that species from the L1 clade might belong to other genera or new genera. This study provides molecular information for further taxonomic and phylogenetic studies of Mytilidae. [ABSTRACT FROM AUTHOR]

The recruitment of intertidal benthic organisms that have planktonic larvae is influenced by hydrodynamics at multiple nested spatial scales, ranging from tens of centimetres to kilometres. Intertidal mussel populations on the south coast of South Africa are known to exhibit higher cover within bays than on open-coast shorelines. This study tested the hypothesis that topographically driven differences in hydrodynamics will result in comparatively higher recruitment within bays. Specifically, we estimated recruitment rates of the native brown mussel Perna perna and the invasive Mediterranean mussel Mytilus galloprovincialis (family Mytilidae) over five spring tidal cycles at bay and open-coast sites at both Algoa Bay and St Francis Bay, and the data were then correlated with upwelling indices derived from wind data. We recorded 3 313 P. perna and 2 485 M. galloprovincialis recruits individually and found that mussel recruitment within bays was as much as two orders of magnitude higher than on open coast. The relationship between recruit numbers and upwelling indices was positive, although non-significant, and markedly stronger for the open-coast sites (where r2 values were 0.51–0.59). These results indicate that better mussel cover within bays can be at least partially explained by higher recruitment rates. [ABSTRACT FROM AUTHOR]

Metabolic rate is a crucial trait shaping organismal physiology, adaptability, and ecological roles, with extensive studies on its allometric relationship with body size. Larger organisms have lower mass-specific metabolic rates, a pattern observed across taxa and ontogeny. Despite numerous hypotheses, no universally accepted theory exists on the biological mechanisms of metabolic allometry, particularly for suborganism-level. We investigated the relationship between body size and metabolic rate as well as mitochondrial characteristics in isolated gill tissue of the marine mussel Mytilus edulis. Results indicated that metabolic allometry patterns observed at the organismal level did not manifest at the tissue level. Our study also revealed that while the density of mitochondria in gill tissue did not differ significantly between large and small individuals, area and perimeter of mitochondrial cross-sections increased significantly with body mass. This finding contrasts with mammalian data, suggesting potential phylogenetic differences. Larger mussels exhibited higher mitochondrial activity, supporting a link between mitochondrial morphology, activity, and growth rates. Our results highlight the importance of mitochondria in mollusk metabolism and growth, warranting further exploration into the mechanisms translating mitochondrial characteristics into growth rates. [ABSTRACT FROM AUTHOR]

There is an international pressure to increase the worldwide expanse of marine mussel farms. However, the mussel farms are challenged with environmental problems such as mucilage aggregate events. Thus, it is essential to assess the effects of mucilage on the mussel aquaculture and to eradicate the harm and socioeconomic effects they confer on society. Our study addressed this issue by establishing a demographic baseline for commercially important mussel species prior to the proposed aquaculture in the area. This baseline was established at a recently set up commercial mussel farm located approximately 4km north of Erdek port and around 2km from Ocaklar port in the Marmara Sea region of Türkiye. Monthly samples of spats attached to the collectors and mussel meat yields were addressed, and seawater temperature and chlorophyll a contents were measured throughout this study (36 months) conducted at a commercial mussel farm. Year-round biological data from 2019 to 2022 were recorded before, during, and after the mucilage event on the Mediterranean mussel, Mytilus galloprovincialis. Moreover, samples were taken from an area inside the mussel aquafarm. As a result of this study, differences before, during, and after the mucilage aggregate event were detected in the number of the Mediterranean mussel spat attached to the collectors and the meat yields of the farmed mussels. This demographic baseline is the only data available, at a sufficient spatial and temporal resolution, for evaluating the effects of a mucilage aggregate event in the mussel aquafarm, and it fills an important data gap for risk assessment. [ABSTRACT FROM AUTHOR]

The powerful adhesion systems of marine organisms have inspired the development of artificial protein-based bioadhesives. However, achieving robust wet adhesion using artificial bioadhesives remains technically challenging because the key element of liquid–liquid phase separation (LLPS)-driven complex coacervation in natural adhesion systems is often ignored. In this study, mimicking the complex coacervation phenomenon of marine organisms, an artificial protein-based adhesive hydrogel (SFG hydrogel) was developed by adopting the LLPS-mediated coacervation of the natural protein silk fibroin (SF) and the anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SF/SDBS complex coacervate enabled precise spatial positioning and easy self-adjustable deposition on irregular substrate surfaces, allowing for tight contact. Spontaneous liquid-to-solid maturation promoted the phase transition of the SF/SDBS complex coacervate to form the SFG hydrogel in situ , enhancing its bulk cohesiveness and interfacial adhesion. The formed SFG hydrogel exhibited intrinsic advantages as a new type of artificial protein-based adhesive, including good biocompatibility, robust wet adhesion, rapid blood-clotting capacity, and easy operation. In vitro and in vivo experiments demonstrated that the SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, thus advancing its clinical applications. Marine mussels utilize the liquid–liquid phase separation (LLPS) strategy to induce the supramolecular assembly of mussel foot proteins, which plays a critical role in strong underwater adhesion of mussel foot proteins. Herein, an artificial protein-based adhesive hydrogel (named SFG hydrogel) was reported by adopting the LLPS-mediated coacervation of natural protein silk fibroin (SF) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SFG hydrogel enabled the precise spatial positioning and easy self-adjustable deposition on substrate surfaces with irregularities, allowing tight interfacial adhesion and cohesiveness. The SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, exhibiting intrinsic advantages as a new type of artificial protein-based bioadhesives. [Display omitted] [ABSTRACT FROM AUTHOR]

Limnoperna fortunei (L. fortunei) (Dunker, 1857), the golden mussel, is an invasive species possessing exceptional environmental adaptability and a destructive impact on water systems and artificial structures. To better conservation of freshwater ecosystems by controlling this mussel, it is essential to study its distribution, potential for invasion, environmental tolerance and biological traits.This paper outlines the distribution of L. fortunei in Asia and South America, as well as its potential for future invasion in freshwater habitats, along with the research methods employed.We find that the mussel had a temperature tolerance range of 8–35 °C and a pH range was 5–10, with some individuals surviving in extreme conditions for extended periods.We find that temperature was a decisive factor for success at reproductive stages, larval development and adult growth.The biological traits of L. fortunei are discussed, focusing on feeding habits, attachment characteristics and locomotion, with an emphasis on byssus structure, foot proteins and adhesion mechanisms. The study elucidates the impact of flow velocity, light exposure and substrate material on their attachment, with the optimal attachment being identified at a flow velocity of 0.3–0.9 m/s. Additionally, the mussel exhibits strong light avoidance performances and a preference for rough surfaces.Extensively‐researched control strategies are classified and summarized, primarily categorized into physical, chemical and biological control, with an outline of their respective strengths and limitations. [ABSTRACT FROM AUTHOR]

The pregnane X receptor (PXR) is a nuclear hormone receptor that plays a pivotal role in regulating gene expression in response to various ligands, particularly xenobiotics. In this context, the aim of this study was to shed light on the ligand affinity and functions of four NR1J1 paralogs identified in the marine mussel Mytilus galloprovincialis, employing a dual-luciferase reporter assay. To achieve this, the activation patterns of these paralogs in response to various toxins, including freshwater cyanotoxins (Anatoxin-a, Cylindrospermopsin, and Microcystin-LR, -RR, and -YR) and marine algal toxins (Nodularin, Saxitoxin, and Tetrodotoxin), alongside natural compounds (Saint John's Wort, Ursolic Acid, and 8-Methoxypsoralene) and microalgal extracts (Tetraselmis, Isochrysis, LEGE 95046, and LEGE 91351 extracts), were studied. The investigation revealed nuanced differences in paralog response patterns, highlighting the remarkable sensitivity of MgaNR1J1γ and MgaNR1J1δ paralogs to several toxins. In conclusion, this study sheds light on the intricate mechanisms of xenobiotic metabolism and detoxification, particularly focusing on the role of marine mussel NR1J1 in responding to a diverse array of compounds. Furthermore, comparative analysis with human PXR revealed potential species-specific adaptations in detoxification mechanisms, suggesting evolutionary implications. These findings deepen our understanding of PXR-mediated metabolism mechanisms, offering insights into environmental monitoring and evolutionary biology research. [ABSTRACT FROM AUTHOR]

Micro-sized particles of synthetic polymers (microplastics) are found in all parts of marine ecosystems. This fact requires intensive study of the degree of danger of such particles to the life activity of hydrobionts and needs additional research. It is evident that hydrobionts in the marine environment are exposed to microplastics modified by biotic and abiotic degradation. To assess the toxic potential of aging microplastic, comparative studies were conducted on the response of cytochemical and genotoxic markers in hemocytes of the mussel Mytilus trossulus (Gould, 1850) after exposure to pristine and photodegraded (UV irradiation) polystyrene microparticles (µPS). The results of cytochemical tests showed that UV-irradiated µPS strongly reduced metabolism and destabilized lysosome membranes compared to pristine µPS. Using a Comet assay, it was shown that the nuclear DNA of mussel hemocytes showed high sensitivity to exposure to both types of plastics. However, the level of DNA damage was significantly higher in mussels exposed to aging µPS. It is suggested that the mechanism of increased toxicity of photo-oxidized µPS is based on free-radical reactions induced by the UV irradiation of polymers. The risks of toxic effects will be determined by the level of physicochemical degradation of the polymer, which can significantly affect the mechanisms of toxicity. [ABSTRACT FROM AUTHOR]

Bivalves are known to be infected by filamentous fungi, many of which have pathogenic and toxicogenic properties, and may represent a risk to human health. The present study investigated the mycological characteristics of Perna perna obtained from Guanabara Bay, Brazil. The mussels were sealed individually in sterile bags, weighed and measured, and the internal organs were examined. The organs were grown in different culture media. All but one of the 31 mussels (96.7%) examined contained fungi, and a total of 84 fungal colonies were isolated. The genera identified were Aspergillus (40.5%), Didymella (35.7%), Penicillium (10.7%), Aureobasidium (1.2%), Cladosporium (1.2%) and Phaeoisaria (1.2%). The molecular sequences obtained 99.8 and 100% identity with Didymella sp., Phaeoisaria sp. and Aureobasidium pullulans, and were deposited in GenBank. This is the first record of Didymella and Phaeoisaria in a bivalve. The digestive gland was the organ with the greatest diversity of fungi genera. A number of the fungi identified here, as Aspergillus awamori, Aspergillus japonicus, Aspergillus niger, Aspergillusversicolor and Aspergillus sydowii, are known to produce mycotoxins and others are opportunistic forms, which reinforces the need for the systematic monitoring of the study area to guarantee the safe exploitation of these bivalves for human consumption. [ABSTRACT FROM AUTHOR]

This study was carried out to determine the effects of cage cultivation on bioecological characteristics of Mytilus galloprovincialis in Güllük Bay Kazıklı Port between May 2013 and May 2014. An integrated multi-trophic aquaculture method was used. The growth and survival rates, age structure and reproductive success of mussels as well as water quality parameters and phytoplankton composition were monitored monthly in two selected stations. Mussels belonging to different size groups exhibited high growth and survival rates during the summer and spring when the temperature was high near the offshore systems. Applying a length-frequency analysis graph created using the shell growth limits, it was found that the mussels reached the marketing length (>50 mm) in 18 months. With this study, it has been revealed that mussel development continued in both stations and the region was suitable for potential mussel farming. [ABSTRACT FROM AUTHOR]

SeviL, a galactoside-binding lectin previously isolated from the mussel Mytilisepta virgata, was demonstrated to trigger apoptosis in HeLa ovarian cancer cells. Here, we show that this lectin can promote the polarization of macrophage cell lines toward an M1 functional phenotype at low concentrations. The administration of SeviL to monocyte and basophil cell lines reduced their growth in a dose-dependent manner. However, low lectin concentrations induced proliferation in the RAW264.7 macrophage cell line, which was supported by the significant up-regulation of TOM22, a component of the mitochondrial outer membrane. Furthermore, the morphology of lectin-treated macrophage cells markedly changed, shifting from a spherical to an elongated shape. The ability of SeviL to induce the polarization of RAW264.7 cells to M1 macrophages at low concentrations is supported by the secretion of proinflammatory cytokines and chemokines, as well as by the enhancement in the expression of IL-6- and TNF-α-encoding mRNAs, both of which encode inflammatory molecular markers. Moreover, we also observed a number of accessory molecular alterations, such as the activation of MAP kinases and the JAK/STAT pathway and the phosphorylation of platelet-derived growth factor receptor-α, which altogether support the functional reprogramming of RAW264.7 following SeviL treatment. These results indicate that this mussel β-trefoil lectin has a concentration-dependent multifunctional role in regulating cell proliferation, phenotype, and death in macrophages, suggesting its possible involvement in regulating hemocyte activity in vivo. [ABSTRACT FROM AUTHOR]

Quantifying the response of marine mussel plaque attachment to wet surfaces remains a significant challenge to a mechanistic understanding of plaque adhesion. Here, we develop a novel, customized microscope system, combined with two-dimensional in situ digital image correlation (DIC), to quantify the in-plane deformation of a deformable substrate that interacts with a mussel plaque under directional tension. By examining the strain field within the substrate, we acquired an understanding of the mechanism by which in-plane traction forces are transmitted from the mussel plaque to the underlying substrate. Finite-element (FE) models were developed to assist in the interpretation of the experimental measurement. Our study revealed a synergistic effect of pulling angle and substrate stiffness on plaque detachment, with mussel plaques anchoring to a 'stiff' substrate at small pulling angles, i.e. natural anchoring angles, having mechanical advantages with higher load-bearing capacity and less plaque deformation. We identify two distinct failure modes, i.e. shear-traction-governed failure (STGF) and normal-traction-governed failure (NTGF). It was found that increasing the stiffness of the substrate or reducing the pulling angle results in a change of the failure mode from NTGF to STGF. Our findings offer new insights into the mechanistic understanding of mussel plaque–substrate interaction, providing a plaque-inspired strategy to develop high-performance and artificial wet adhesion. [ABSTRACT FROM AUTHOR]

Introduction: Many marine organisms have a biphasic life cycle that transitions between a swimming larva with a more sedentary adult form. At the end of the first phase, larvae must identify suitable sites to settle and undergo a dramatic morphological change. Environmental factors, including photic and chemical cues, appear to influence settlement, but the sensory receptors involved are largely unknown. We targeted the protein receptor, opsin, which belongs to large superfamily of transmembrane receptors that detects environmental stimuli, hormones, and neurotransmitters. While opsins are well-known for light-sensing, including vision, a growing number of studies have demonstrated light-independent functions. We therefore examined opsin expression in the Pteriomorphia, a large, diverse clade of marine bivalves, that includes commercially important species, such as oysters, mussels, and scallops. Methods: Genomic annotations combined with phylogenetic analysis show great variation of opsin abundance among pteriomorphian bivalves, including surprisingly high genomic abundance in many species that are eyeless as adults, such as mussels. Therefore, we investigated the diversity of opsin expression from the perspective of larval development. We collected opsin gene expression in four families of Pteriomorphia, across three distinct larval stages, i.e., trochophore, veliger, and pediveliger, and compared those to adult tissues. Results: We found larvae express all opsin types in these bivalves, but opsin expression patterns are largely species-specific across development. Few opsins are expressed in the adult mantle, but many are highly expressed in adult eyes. Intriguingly, opsin genes such as retinochrome, xenopsins, and Go-opsins have higher levels of expression in the later larval stages when substrates for settlement are being tested, such as the pediveliger. Conclusion: Investigating opsin gene expression during larval development provides crucial insights into their intricate interactions with the surroundings, which may shed light on how opsin receptors of these organisms respond to various environmental cues that play a pivotal role in their settlement process. [ABSTRACT FROM AUTHOR]

The ionic properties of strontium (Sr), a significant artificial radionuclide in the marine environment, were estimated using a stable nuclide-substituting experimental system under controlled laboratory conditions. The bio-accumulation of Sr and its impacts, as well as any possible hidden mechanisms, were evaluated based on the physiological alterations of the sentinel blue mussel Mytilus edulis. The mussels were exposed to a series of stress-inducing concentrations, with the highest solubility being 0.2 g/L. No acute lethality was observed during the experiment, but sublethal damage was evident. Sr accumulated in a tissue-specific way, and hemolymph was the target, with the highest accumulating concentration being 64.46 µg/g wet weight (ww). At the molecular level, increases in the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) and changes in ROS components (H2O2, O2−, and -OH) and antioxidant system activity indicated that the redox equilibrium state in hemocytes was disturbed. Furthermore, the rise in the hemocyte micronucleus (MN) rate (4‰ in the high-concentration group) implied DNA damage. At the cellular level, the structures of hemocytes were damaged, especially with respect to lysosomes, which play a crucial role in phagocytosis. Lysosomal membrane stability (LMS) was also affected, and both acid phosphatase (ACP) and alkaline phosphatase (AKP) activities were reduced, resulting in a significant decline in phagocytosis. The hemolymph population structure at the organ level was disturbed, with large changes in hemocyte number and mortality rate, along with changes in component ratios. These toxic effects were evaluated by employing the adverse outcome pathway (AOP) framework. The results suggested that the disruption of intracellular redox homeostasis is a possible explanation for Sr-induced toxicity in M. edulis. [ABSTRACT FROM AUTHOR]

Hybridization among related species is now recognized as common but it remains unclear how hybrid zones persist for prolonged periods. Here, we test the hypothesis that selection in different components of the life cycle may stabilize a hybrid zone. A hybrid zone occurs in southwest England between the marine mussels Mytilus edulis and M. galloprovincialis. Previous studies have found strong directional selection against alleles from M. edulis occurs among hybrids in the adult stage. Traditional hybrid zone models argue that alleles that are selected within the hybrid zone are replaced by migration from neighboring parental population into the hybrid zone. In this system, however, migration occurs out of this hybrid zone into neighboring parental populations. This hybrid zone should therefore be unstable and dissipate, yet this zone has persisted for more than 30 years. We tested and rejected the hypothesis that differences in fecundity may select for M. edulis alleles within this hybrid zone and thus counter the selection observed against these alleles among adults. We also tested the hypothesis that selection during the larval stage may counter selection against M. edulis alleles in the adult stage. We found that selection favors M. edulis alleles during the veliger stage of larval development. The direction and strength of selection during the larval stage are sufficient to counter strong selection during the adult portion of the life cycle. This hybrid zone is stabilized by opposing forms of directional selection operating in different portions of the life cycle. [ABSTRACT FROM AUTHOR]

Levels of some heavy metal ions were determined in water samples of marine mussels Brachidontes pharaonis collected from the shoreline of the National Institute of Oceanography and Fisheries (NIOF), the Gulf of Suez, Egypt, during the period from June 2019 to May 2020. The objective of the present study was to analyze the seasonal concentrations of some heavy metals (Fe, Co, Ni, Cu, Zn, Pb, Mn, and Cd) that have environmental and health interests in the Gulf of Suez using the bivalve Brachidontes pharaonis (Fischer, 1876) as a biological monitor. The samples were collected seasonally from the site and divided into three size groups. The analyses for the detection of the selected metal concentrations were carried out by flame atomic absorption spectrophotometer. The results showed that the mean concentrations of heavy metals in water were 0.07, 0.64, 0.71, 4.66, 0.26, 0.08, 12.40, 0.07µg/L for Cd, Pb, Cu, Zn, Ni, Co, Fe, and Mn, respectively. With regards to assessed metals in the soft tissues, an inverse relationship was found between metal concentration and bivalve size. According to the collected data, the present study area was varied between low to moderate contamination. This change occurred in conjunction with the increase of industrial activities around the study area. [ABSTRACT FROM AUTHOR]

Simple Summary: Perumytilus purpuratus is a mussel species that is broadly distributed along the latitudinal gradient from the Southern Pacific to the Atlantic Ocean. Along its distribution, P. purpuratus has been historically considered as one species. However, in the last decade, evidence has supported the hypothesis of two geographically divergent lineages. Within this context, we explore the evolutionary history of this inter-oceanic mussel, linking both sperm acrosome variability and molecular analyses of males at the geographic macroscale. In general, our results were in agreement with the genetic divergence that was previously reported, and showing two north and south lineage. Furthermore, our comprehensive sampling effort enabled us to precisely determine both the latitudinal positions of morpho-genetic break, which was identified at 37° S on the Pacific coast, and a probable hybridization zone at 38° S. In addition, we found new southern sperm variants, longer than previously reported. Overall, our results support the hypothesis of historical events and postglacial recolonization as causal phenomena for the observed divergences. Finally, we consider that, despite uncertainties in the taxonomy of P. purpuratus, the morpho-genetic divergence between the north and south P. purpuratus lineages indicates that they do not constitute the same Evolutionary Significant Unit and, therefore, they should be considered as separate entities. In recent years, advances in analyses of the sperm morphology and genetics of Perumytilus purpuratus have allowed to two evolutionary scenarios for this mussel to be suggested: (1) the scenario of cryptic species and (2) the scenario of incipient or in progress speciation. For a better understanding of the evolutionary history of P. purpuratus, we performed extensive sampling along a latitudinal gradient of ca. 7180 km of coastline—from the Southern Pacific Ocean to the Atlantic Ocean—and we delved deeper into the sperm morphology of P. purpuratus, exploring its association with the phylogeny and population genetics to determine whether the variability in sperm traits between the northern and southern regions was a signal of cryptic or incipient species. Overall, our results showed that sperm sizes were strongly correlated with the genetic structure in males of P. purpuratus. We identified at 37° S on the Pacific coast a coincident break of both sperm size and genetic disruption that can be explained by historical events and postglacial recolonization as causal phenomena for the observed divergences. Furthermore, evidence of genetic admixture between lineages was found at 38° S, suggesting the presence of an introgressive hybridization zone and incomplete reproductive isolation in an in fraganti or incipient speciation process. [ABSTRACT FROM AUTHOR]

The invasive charru mussel Mytella strigata (Hanley, 1843) was first reported by fishermen in the upper Gulf of Thailand in 2017 and was scientifically surveyed in November 2018. A survey in August 2023 demonstrated that the mussel had not spread significantly in the region in nearly five years. Populations remained dense in aquaculture ponds and the Bangpakong River estuary where it was most abundant in 2018, but M. strigata occurred at only one of 10 rocky shore sites on the open coast. Size frequency histograms for all populations of M. strigata sampled were unimodal, suggesting there was one spawning season, but settlement apparently occurred at different times at the various sites. At sites where M. strigata occurred with the Asian green mussel Perna viridis (Linnaeus, 1758), the evidence that M. strigata was outcompeting P. viridis was uncertain. Data obtained during the 2018 and 2023 surveys provide a sound basis for monitoring the status of M. strigata in the upper Gulf of Thailand in the future. There is an urgent requirement to undertake basic biological research on population parameters such as reproductive periodicity, growth rates and, in particular, the environmental and economics of the widespread invasion of this species. [ABSTRACT FROM AUTHOR]

Our understanding of basic cellular processes has mostly been provided by mammalian cell culture, and by some non-mammalian vertebrate and few invertebrate cell culture models. Developing reliable culture conditions for non-model organisms is essential to allow investigation of more unusual cellular processes. Here, we investigate how cells isolated from different tissues of the marine mussel Mytilus edulis thrive and survive in vitro in the hope of establishing a suitable laboratory model for the investigation of cellular mechanisms specific to these bivalve mollusks. We found that cells dissociated from mantle tissue attached to the culture vessels and proliferated well in vitro, whereas cells isolated from gills, although remaining viable, did not maintain divisions over three to four weeks in culture. We used antibodies against the germ-line marker DEAD-box helicase 4 (DDX4), also known as VASA, and the epithelial cell marker cytokeratin to distinguish different cell types in culture. DDX4-positive cells were predominant in 25-day-old cultures from male mantles. Cells from other tissues remained in low numbers and did not seem to change in composition over time. Overall, the culture conditions described here allow an efficient selection of male germ cells that could be used to study specific cellular mechanisms in vitro. [ABSTRACT FROM AUTHOR]

The study of hybrid zones offers important insights into speciation. Earlier studies on hybrid populations of the marine mussel species Mytilus edulis and Mytilus galloprovincialis in SW England provided evidence of admixture but were constrained by the limited number of molecular markers available. We use 57 ancestry‐informative SNPs, most of which have been mapped genetically, to provide evidence of distinctive differences between admixed populations in SW England and asymmetrical introgression from M. edulis to M. galloprovincialis. We combine the genetic study with analysis of phenotypic traits of potential ecological and adaptive significance. We demonstrate that hybrid individuals have brown mantle edges unlike the white or purple in the parental species, suggesting allelic or non‐allelic genomic interactions. We report differences in gonad development stage between the species consistent with a prezygotic barrier between the species. By incorporating results from publications dating back to 1980, we confirm the long‐term stability of the hybrid zone despite higher viability of M. galloprovincialis. This stability coincides with a dramatic change in temperature of UK coastal waters and suggests that these hybrid populations might be resisting the effects of global warming. However, a single SNP locus associated with the Notch transmembrane signalling protein shows a markedly different pattern of variation to the others and might be associated with adaptation of M. galloprovincialis to colder northern temperatures. [ABSTRACT FROM AUTHOR]

The impacts of climate change on marine organisms have been increasingly documented in laboratory and experimental studies. However, the use of different taxonomic groupings and the assessment of a range of processes make identifying overall trends challenging. Meta-analysis has been used to determine general trends, but coarse taxonomic granularity may mask phylogenetically specific responses. Bivalve molluscs are a data-rich clade of ecologically and economically important calcifying marine taxa that allow for the assessment of species-specific vulnerability across developmental stages. Drawing on the large body of available literature, we conduct a meta-analysis of 203 unique experimental set-ups in order to examine how bivalve growth responds to increased water temperature, acidity, deoxygenation, and changes in salinity in 10 climate change stressor combinations. This is the most complete examination of bivalve responses to date and shows that anthropogenic climate change will disproportionally affect particular families, suggesting taxonomic differentiation in climate change response. Specifically, Mytilidae, Ostreidae, and Pectinidae (67 % of experiments) respond with negative effect sizes for all individual stressors, whereas responses in Pinnidae, Tellinidae, and Veneridae are more complex. Our analysis shows that earlier studies reporting negative impacts on bivalves are driven by only three or four well-studied, commercially important families. Despite the taxonomic differentiation, almost all drivers and their combinations have significant negative effects on growth. The synergistic impacts of deoxygenation, acidification, and temperature result in the largest negative effect size. Infaunal taxa, including Tellinidae and Veneridae, appear more resistant to warming and oxygen reduction than epifaunal or motile taxa, but this difference between the two taxa is also based on a small number of data points. The current focus of experimental set-ups on commercially important taxa and families within a small geographic range creates gaps in the understanding of global impacts on these economically important foundation organisms. [ABSTRACT FROM AUTHOR]

Simple Summary: The smooth-shelled marine mussel Mytilus galloprovincialis maintains its genetic integrity as a species on a worldwide scale. Current population genetic analyses confirm the largest divergence of M. trossulus compared to the rest of congeneric species and place M. chilensis as an intermediate taxon between M. galloprovincialis and M. edulis. Unlike previous reports, M. galloprovincialis from the Atlantic Northeast is the most likely source of exotic settlements worldwide. As a super-adaptive species, M. galloprovincialis should not be considered invasive in a human-like supremacist manner, but rather as a flexible evolutionary species (FES). The worldwide distribution of this species suggests that it is naturally endowed with plastic adaptation. Therefore, it could counteract stressful conditions and provide intergeneric ecological opportunities in the face of climatic rarefaction of world coasts. The Mediterranean mussel Mytilus galloprovincialis is distributed in both hemispheres either natively or introduced. The updated population genetic distribution of this species provides a useful knowledge against which future distribution shifts could be assessed. This study, performed with seven microsatellite markers and three reference species (M. edulis, M. chilensis and M. trossulus), aimed to determine the scenario of genetic divergence between 15 samples of M. galloprovincialis from 10 localities in Europe, Africa, Asia, Australia, North America and South America. In agreement with previous data, M. trossulus was the most divergent taxon of the genus, but M. chilensis appeared as an intermediate taxon between M. edulis and M. galloprovincialis, though closer to this latter. M. galloprovincialis from the Atlantic Northeast appears as the most likely source of worldwide exotic settlements instead of the previously thought Mediterranean population. The successful worldwide establishment of M. galloprovincialis suggests it is a flexible evolutionary species (FES), i.e., a species or population whose genetic background allows it to rapidly adapt to changing environments. This natural endowed plastic adaptation makes it a candidate resilient species amidst the ongoing climatic change. [ABSTRACT FROM AUTHOR]

The purpose of this application, under Articles 23.9.3 and 81.1 of the Code, is to conserve the current usage of the specific name of the northeast Pacific Ocean marine mussel Mytilus californianusConrad, 1837, the identity of which has never been questioned. After examining the type specimens of Mytilus zonariusLamarck, 1819 and Mytilus canalisLamarck, 1819, Huber (2010) concluded that they were M. californianus and used the former as its valid name. Neither Mytilus zonarius nor M. canalis have been used as the valid name of Mytilus californianus between 1819 and 2010. The name Mytilus californianus has been used as the valid name of this species in thousands of publications between 1837 and 2020. It is proposed to conserve the name Mytilus californianusConrad, 1837 by reversal of precedence with the names Mytilus zonariusLamarck, 1819 and Mytilus canalisLamarck, 1819. [ABSTRACT FROM AUTHOR]

IntroductionMany marine organisms have a biphasic life cycle that transitions between a swimming larva with a more sedentary adult form. At the end of the first phase, larvae must identify suitable sites to settle and undergo a dramatic morphological change. Environmental factors, including photic and chemical cues, appear to influence settlement, but the sensory receptors involved are largely unknown. We targeted the protein receptor, opsin, which belongs to large superfamily of transmembrane receptors that detects environmental stimuli, hormones, and neurotransmitters. While opsins are well-known for light-sensing, including vision, a growing number of studies have demonstrated light-independent functions. We therefore examined opsin expression in the Pteriomorphia, a large, diverse clade of marine bivalves, that includes commercially important species, such as oysters, mussels, and scallops.MethodsGenomic annotations combined with phylogenetic analysis show great variation of opsin abundance among pteriomorphian bivalves, including surprisingly high genomic abundance in many species that are eyeless as adults, such as mussels. Therefore, we investigated the diversity of opsin expression from the perspective of larval development. We collected opsin gene expression in four families of Pteriomorphia, across three distinct larval stages, i.e., trochophore, veliger, and pediveliger, and compared those to adult tissues.ResultsWe found larvae express all opsin types in these bivalves, but opsin expression patterns are largely species-specific across development. Few opsins are expressed in the adult mantle, but many are highly expressed in adult eyes. Intriguingly, opsin genes such as retinochrome, xenopsins, and Go-opsins have higher levels of expression in the later larval stages when substrates for settlement are being tested, such as the pediveliger.ConclusionInvestigating opsin gene expression during larval development provides crucial insights into their intricate interactions with the surroundings, which may shed light on how opsin receptors of these organisms respond to various environmental cues that play a pivotal role in their settlement process.

Aim. The aim of the study was to compare the specificity and sensitivity of responses of stress and toxicity to Cpz in marine and freshwater species of bivalve molluscs. Methods. The bivalve molluscs Mytilus galloprovincialis and Unio tumidus were collected in Messina, Italy and Ternopil region, Ukraine correspondingly. Two low Cpz concentrations (Cpz I: 12 ng L–1; Cpz II: 12 (M. galloprovincialis) or 18 (U. tumidus) μg L–1) were administered to molluscs for 14 days. The set of 16 studied parameters included the cytotoxicity indexes (lysosomal membrane stability, apoptotic enzymes caspase-3 and cathepsin D (CtD)), o xidative/reductive stress responses (superoxide dismutase (SOD) and catalase (CAT) activities, the levels of protein carbonyls (PC) and products of lipid peroxidation (TBARS), glutathione (GSH&GSSG), NAD+&NADH), metallothionein (total and Zn-bound) concentration, the biotransformation enzymes CYP450-dependent EROD, glutathione S-transferase (GST), and GTP-ase dynamin in the digestive gland with some inter-species differences in this spectrum. The applied spectrophotometric and chromatographic methods are described thoroughly in our previous work [6]. Results and Discussion. In the hepatocytes of rat, Cpz causes the biotransformation upregulation [7]. In our study, the activity of EROD increased both in M. galloprovincialis and U. tumidus, depending on the concentration and, particularly, in the Cpz II group of U. tumidus (by three times). This conversion of Cpz can result in the reactive metabolite formation [7]. According to this data, the inhibition or absence of the changes in the EROD activity in the Cpz I group of U. tumidus and Cpz II group of M. galloprovincialis can delay Cpz toxicity. On the other hand, the toxic product of biotransformation, quinoneimine is known to be eliminated by the GSH-dependent GST which activity was increased up to 63% in the Cpz I and II groups of marine mussels. Since in the freshwater mussels GST activity decreased in both exposures, the higher toxicity of Cpz was expected. Moreover, the GTP-ase dynamin activation in the Cpz I group of U. tumidus confirms the impact of this pharmaceutical on the clathrin-dependent endocytosis [8]. Conclusions. Summarizing, adverse outcome pathways related to the effect of Cpz on vertebrates in the μM concentration, were indicated in the mussels under the pM — nM concentrations with distinct inter-species concentration-related dependence, and the responses of stress were similar in both species. Particularly, marine molluscs can be a perspective model for evaluating Cpz adverse effects intrinsic for the higher vertebrates. [ABSTRACT FROM AUTHOR]

The study focused on understanding the reproductive biology of Pinctada margaritifera, commonly known as the black-lipped pearl oyster, which holds significant economic importance due to its production of Tahitian cultured pearls. Research conducted in Mabahiss Bay, the Red Sea, Egypt throughout 2022 provided crucial insights into the reproductive cycle of P. margaritifera. The species exhibits protandric hermaphroditism, transitioning from male to female during its growth. Shell sizes inversely correlated with sex distribution, with a sex ratio of 1.05: 1.0: 0.1 for females, males, and undifferentiated individuals, respectively. The study identified a distinct spawning phase from June to October, peaking in July and August. Analyses of gonad index fluctuations in females and males provided additional understanding of reproductive dynamics. Among the methods tested to stimulate spawning, hormones and gonad stripping yielded positive results. The research also delved into the timing and early development stages of eggs and larvae of P. margaritifera. [ABSTRACT FROM AUTHOR]

Sea levels across the planet are rising, particularly along the eastern coast of the United States. Climate‐induced sea level rise can result in the inundation and intrusion of seawater into freshwater drainages. This would alter salinity regimes and lead to the salinization of coastal freshwater ecosystems. Increased salinity levels in freshwater can negatively affect freshwater‐dependent species, including native mussels belonging to the order Unionida, which are highly sensitive to changes in water quality. Sea salt is largely made up of sodium and chloride ions, forming sodium chloride, a known toxicant to freshwater mussels. However, sea salt is a mixture that also contains other major ions, including potassium, sulfate, calcium, strontium, and magnesium, among others. Freshwater mussels exposed to sea salt would be exposed to each of the sea salt ions at the same time, resulting in a mixture toxicity effect. The mixture toxicity of these ions on early life stages of freshwater mussels is largely unknown because most research to date has evaluated individual salt ions in relative isolation. Therefore, we conducted acute toxicity tests on early life stages (glochidia and juvenile) of three freshwater mussel species that inhabit Atlantic Slope drainages (nonsalinity‐adapted Atlanticoncha ochracea, salinity‐adapted A. ochracea, Sagittunio nasutus, and Utterbackiana implicata). Glochidia and juveniles of each species were exposed to a control and six concentrations of Instant Ocean® Sea Salt (IOSS), a synthetic sea salt that closely resembles the ionic composition of natural sea salt. Exposure concentrations were 1 part(s) per thousand (ppt), 2 ppt, 8.5 ppt, 12.5 ppt, 17 ppt, and 34 ppt. We calculated the median effect concentration (EC50) for each of the eight acute toxicity tests and found that glochidia were more sensitive than juveniles to IOSS. At hour 24 EC50s for the glochidia ranged from 0.38 to 3.6 ppt, with the most sensitive freshwater mussel being the nonsalinity‐adapted A. ochracea, exhibiting an EC50 of 0.38 ppt (95% confidence interval [CI] 0.33–0.44). Juvenile freshwater mussels exhibited EC50s at hour 96 ranging from 5.0 to 10.4 ppt, with the least sensitive freshwater mussel being the nonsalinity‐adapted A. ochracea, exhibiting an EC50 of 10.4 ppt (95% CI 9.1–12.0). Our results show that acute exposure to sea salt adversely affects freshwater mussel viability, particularly glochidia. This information can be used to enhance freshwater mussel conservation strategies in regions that are or will be impacted by climate‐induced sea level rise and associated freshwater salinization. Environ Toxicol Chem 2023;42:2478–2489. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

The growing human population requires more food each year, and seafood products can help meet this demand if clean water resources are available for their growth. Farmed and wild mussels are environmentally friendly seafood with many health benefits to human consumers, but they can also pose a health risk if they are harvested from areas where marine anthropogenic pollution is uncontrolled or unmonitored. While the coastline in South Africa has long been assumed to be pristine, a growing number of recent studies are raising contamination concerns. Baseline studies establish a wide range of anthropogenic pollutants to be present in the marine environment, specifically in urbanised or industrialised areas like major cities or harbours. This review summarises how mussels could pose health risks to human consumers and the current research that is being conducted by private researchers and institutions in South Africa. The review emphasises the need for more research in the field and for governmental pollution monitoring data to be released to the public. [ABSTRACT FROM AUTHOR]

NF-E2-related factor 2 (Nrf2) plays a crucial role in the oxidative regulatory process, which could trigger hundreds of antioxidant elements to confront xenobiotics. In the previous study, we identified Nrf2 from the marine mussel Mytilus coruscus, and the findings demonstrated that McNrf2 effectively protected the mussels against oxidative stress induced by benzopyrene (Bap). In order to delve deeper into the underlying mechanism, we utilized Chromatin Immunoprecipitation followed by sequencing (ChIP-seq) technology to systematically identify potential novel target genes of McNrf2. A total of 3,465 potential target genes were screened, of which 219 owned binding sites located within the promoter region. During subsequent experimental verification, it was found that McSLC35E2, a candidate target gene of McNrf2, exhibited negative regulation by McNrf2, as confirmed through dual luciferase and qRTPCR detection. Further, the enzyme activity tests demonstrated that McNrf2 could counteract Bap induced oxidative stress by inhibiting McSLC35E2. The current study provides valuable insights into the application of ChIP-seq technology in the research of marine mollusks, advancing our understanding of the key role of Nrf2 in antioxidant defense mechanisms, and highlighting the significance of SLC35E2 in the highly sophisticated regulation of oxidative stress response in marine invertebrates. [ABSTRACT FROM AUTHOR]

The accumulation of trace metals in the shells of bivalves allows quantitative assessments of environmental pollution and helps to reconstruct paleo aquatic environments. However, the understanding on how marine and freshwater mollusks control the level of trace elements in their shells remains very limited. Here, we compared the trace element composition of marine and freshwater bivalves from boreal and subarctic habitats, using examples of widely distributed species of marine (Mytilus edulis, M. trossulus) and freshwater (Anodonta anatina, Unio sp., Beringiana beringiana) mussels. Sizable differences in several trace element concentrations were detected between different species, depending on their environmental niches. A multiparametric statistical treatment of the shell's elemental composition allowed to distinguish the impact of external factors (water and sediment chemical composition) from active metabolic (biological) control. In particular, the obtained results demonstrated that Ba:Ca and Pb:Ca ratios in mussels' shells are closely related to the primary productivity of aquatic ecosystems. The Mn:Ca ratio allowed to constrain the environmental conditions of mussels' species depending on the trophic state of inhabited waterbody. Overall, the marine mussels exhibited stronger biological control of trace element accumulation, whereas trace element pattern in shells of freshwater mussels was chiefly controlled by environmental factors. The obtained results might help to use the trace element composition of bivalves in distinguishing marine and freshwater habitats of mollusks in paleo environments. [ABSTRACT FROM AUTHOR]

We have shown in the past decade, for the first time in a bivalve mollusc, detection, isolation, and purification of β-1,3 glucan binding protein (β-GBP) in the plasma of the marine mussel Perna viridis and demonstrated its role in a nonself-induced activation of plasma prophenoloxidase system. In this study, we present evidence for its ability to function as an opsonin during phagocytosis of trypsinized yeast cells by the hemocytes of P. viridis. The in vitro pretreatment of target cells (trypsinized yeast cells) with β-GBP enhanced the phagocytic response of hemocytes. Such β-GBP-mediated enhanced phagocytic response appeared to be dose dependent. This opsono-phagocytic response could be inhibited by the presence of laminarin (a polymer of β-1,3 glucans), glucose, as well as polyclonal antibodies raised against β-GBP. These observations clearly indicate that the plasma β-GBP can possibly recognize and bind to β-1,3 glucans on the surface of targets and facilitate hemocyte recognition processes possibly by forming a bridge between the hemocytes and the target, consequently leading to opsono-phagocytosis. These observations together with our earlier annotations indicate the multifunctional potential of plasma β-GBP in the marine mussel P. viridis. [ABSTRACT FROM AUTHOR]