Multifunctional Cell Regulation Activities of the Mussel Lectin SeviL: Induction of Macrophage Polarization toward the M1 Functional Phenotype.

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 ß-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.

Genome Report: A chromosome-scale Mytilus edulis genome assembly for aquaculture, marine ecology and evolution.

The smooth-shelled blue mussel, Mytilus edulis is part of the Mytilus species complex, encompassing at least three putative species: M. edulis, M. galloprovincialis and M. 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 Mytilus 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 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.

Integrated transcriptomic and metabolomic approaches reveal molecular response and potential biomarkers of the deep-sea mussel Gigantidas platifrons to copper exposure.

Metal pollution caused by deep-sea mining activities has potential detrimental effects on deep-sea ecosystems. However, our knowledge of how deep-sea organisms respond to this pollution is limited, given the challenges of remoteness and technology. To address this, we conducted a toxicity experiment by using deep-sea mussel Gigantidas platifrons as model animals and exposing them to different copper (Cu) concentrations (50 and 500 µg/L) for 7 days. Transcriptomics and LC-MS-based metabolomics methods were employed to characterize the profiles of transcription and metabolism in deep-sea mussels exposed to Cu. Transcriptomic results suggested that Cu toxicity significantly affected the immune response, apoptosis, and signaling processes in G. platifrons. Metabolomic results demonstrated that Cu exposure disrupted its carbohydrate metabolism, anaerobic metabolism and amino acid metabolism. By integrating both sets of results, transcriptomic and metabolomic, we find that Cu exposure significantly disrupts the metabolic pathway of protein digestion and absorption in G. platifrons. Furthermore, several key genes (e.g., heat shock protein 70 and baculoviral IAP repeat-containing protein 2/3) and metabolites (e.g., alanine and succinate) were identified as potential molecular biomarkers for deep-sea mussel's responses to Cu toxicity. This study contributes novel insight for assessing the potential effects of deep-sea mining activities on deep-sea organisms.

Opsin expression varies across larval development and taxa in pteriomorphian bivalves.

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.

Linking Acrosome Size and Genetic Divergence in an Inter-Oceanic Mussel from the Pacific and Atlantic Coasts: A Case of Incipient Speciation?

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.

The role of solar radiation and tidal emersion on oxidative stress and glutathione synthesis in mussels exposed to air.

Preparation for oxidative stress (POS) is a widespread adaptive response to harsh environmental conditions, whose hallmark is the upregulation of antioxidants. In contrast to controlled laboratory settings, animals are exposed to multiple abiotic stressors under natural field conditions. Still, the interplay between different environmental factors in modulating redox metabolism in natural settings remains largely unexplored. Here, we aim to shed light on this topic by assessing changes in redox metabolism in the mussel Brachidontes solisianus naturally exposed to a tidal cycle. We compared the redox biochemical response of mussels under six different natural conditions in the field along two consecutive days. These conditions differ in terms of chronology, immersion/emersion, and solar radiation, but not in terms of temperature. Animals were collected after being exposed to air early morning (7:30), immersed during late morning and afternoon (8:45-15:30), and then exposed to air again late afternoon towards evening (17:45-21:25), in two days. Whole body homogenates were used to measure the activity of antioxidant (catalase, glutathione transferase and glutathione reductase) and metabolic (glucose 6-phosphate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase and pyruvate kinase) enzymes, reduced (GSH) and disulfide (GSSG) glutathione levels, and oxidative stress markers (protein carbonyl and thiobarbituric acid reactive substances). Air and water temperature remained stable between 22.5 °C and 26 °C during both days. Global solar radiation (GSR) greatly differed between days, with a cumulative GSR of 15,381 kJ/m2 for day 1 and 5,489 kJ/m2 for day 2, whose peaks were 2,240 kJ/m2/h at 14:00 on day 1 and 952 kJ/m2/h at 12:00 on day 2. Compared with animals underwater, emersion during early morning did not elicit any alteration in redox biomarkers in both days. Air exposure for 4 h in the late afternoon towards evening caused oxidative damage to proteins and lipids and elicited GSH synthesis in animals that had been previously exposed to high GSR during the day. In the following day, when GSR was much lower, exposure to air under the same conditions (duration, time, and temperature) had no effect on any redox biomarker. These findings suggest that air exposure under low-intensity solar radiation is not sufficient to trigger POS in B. solisianus in its natural habitat. Thus, natural UV radiation is possibly a key environmental factor that combined to air exposure induces the POS-response to the stressful event of tidal variation in this coastal species.

The Complete Mitochondrial Genome of Mytilisepta virgata (Mollusca: Bivalvia), Novel Gene Rearrangements, and the Phylogenetic Relationships of Mytilidae.

The circular mitochondrial genome of Mytilisepta virgata spans 14,713 bp, which contains 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 22 transfer RNA genes. Analysis of the 13 PCGs reveals that the mitochondrial gene arrangement of Mytilisepta is relatively conserved at the genus level. The location of the atp8 gene in Mytilisepta keenae differs from that of other species. However, compared with the putative molluscan ancestral gene order, M. virgata exhibits a high level of rearrangement. We constructed phylogenetic trees based on concatenated 12 PCGs from Mytilidae. As a result, we found that M. virgata is in the same clade as other Mytilisepta spp. The result of estimated divergence times revealed that M. virgata and M. keenae diverged around the early Paleogene period, although the oldest Mytilisepta fossil was from the late or upper Eocene period. Our results provide robust statistical evidence for a sister-group relationship within Mytilida. The findings not only confirm previous results, but also provide valuable insights into the evolutionary history of Mytilidae.

Latitudinal variation and plasticity in response to temperature in Geukensia demissa.

As global temperatures warm, species must adapt to a changing climate or transition to a different location suitable for their survival. Understanding the extent to which species are able to do so, particularly keystone species, is imperative to ensuring the survival of key ecosystems. The ribbed mussel Geukensia demissa is an integral part of salt marshes along the Atlantic coast of North America. Spatial patterns of genomic and phenotypic divergence have been previously documented, although their link with coastal environmental variation is unknown. Here, we study how populations of G. demissa in the northern (Massachusetts) and southern (Georgia) portions of the species range respond to changes in temperature. We combine assays of variation in oxygen consumption and RNA transcriptomic data with genomic divergence analyses to identify how separate populations of G. demissa may vary in distinct thermal environments. Our results show differences in constitutive oxygen consumption between mussels from Georgia and Massachusetts, as well as shared and disparate patterns of gene expression across temperature profiles. We also find that metabolic genes seem to be a strong component of divergence between these two populations. Our analysis highlights the importance of studying integrative patterns of genomic and phenotypic variation in species that are key for particular ecosystems, and how they might respond to further changes in climate.

Mitochondrial genomic analyses provide new insights into the "missing" atp8 and adaptive evolution of Mytilidae.

BACKGROUND: Mytilidae, also known as marine mussels, are widely distributed in the oceans worldwide. Members of Mytilidae show a tremendous range of ecological adaptions, from the species distributed in freshwater to those that inhabit in deep-sea. Mitochondria play an important role in energy metabolism, which might contribute to the adaptation of Mytilidae to different environments. In addition, some bivalve species are thought to lack the mitochondrial protein-coding gene ATP synthase F0 subunit 8. Increasing studies indicated that the absence of atp8 may be caused by annotation difficulties for atp8 gene is characterized by highly divergent, variable length. RESULTS: In this study, the complete mitochondrial genomes of three marine mussels (Xenostrobus securis, Bathymodiolus puteoserpentis, Gigantidas vrijenhoeki) were newly assembled, with the lengths of 14,972 bp, 20,482, and 17,786 bp, respectively. We annotated atp8 in the sequences that we assembled and the sequences lacking atp8. The newly annotated atp8 sequences all have one predicted transmembrane domain, a similar hydropathy profile, as well as the C-terminal region with positively charged amino acids. Furthermore, we reconstructed the phylogenetic trees and performed positive selection analysis. The results showed that the deep-sea bathymodiolines experienced more relaxed evolutionary constraints. And signatures of positive selection were detected in nad4 of Limnoperna fortunei, which may contribute to the survival and/or thriving of this species in freshwater. CONCLUSIONS: Our analysis supported that atp8 may not be missing in the Mytilidae. And our results provided evidence that the mitochondrial genes may contribute to the adaptation of Mytilidae to different environments.

Microbiological quality of the water in collection areas and the tissue of Mytella falcata-Cananéia (SP, Brazil).

Changes in fauna and abiotic factors in estuaries are a consequence of their exploitation; thus, bivalve mollusks, as they filter, are widely used as environmental bioindicators. The aim of this study was to analyze the existence of seasonal variation in the concentration of total coliforms (TC) and thermotolerant coliforms (Ct), in addition to correlating the data obtained with the salinity and temperature in collection areas of Mytella falcata and the soft tissue cultivated in the Estuarine Complex of Cananéia. Two biweekly samples of water and tissue were taken, for 12 consecutive months, in nine cultivation areas of M. falcata. The analysis of the water samples showed that the Fisheries Institute, Mosquiteiro, and Itapitangui have high TC densities, with respective annual averages of 772.22, 592.67, and 563.75 most probable number (MPN).100 ml-1 . The highest concentrations of TC and Ct occurred in the summer, in most areas. There was a decrease in both TC and Ct with increasing salinity. However, there was an increase in Ct with increasing temperature. The soft tissue showed TC densities from 9 to 26 MPN.100 ml-1 and Ct densities from 6 to 14 MPN.100 ml-1 , displaying the highest counts in the summer. Places where coliforms were found in high concentrations could indicate contamination, because Ct do not support higher salinities for a long time. PRACTITIONER POINTS: The general mean was 77.64 (total coliforms) and 39.35 (thermotolerant) MPN.100 ml-1 . Annual average (thermotolerant) exceeded the permitted Brazilian limit in five points. Higher concentrations of total and thermotolerant coliforms occurred in the summer. In mollusk's tissue, concentrations of thermotolerant were 6.30 to 26.16 MPN.100 g-1 . Coliforms' MPN varied with increasing salinity and temperature.

Plastic and natural inorganic microparticles do not differ in their effects on adult mussels (Mytilidae) from different geographic regions.

Microplastics are ubiquitous in the marine environment and studies on their effects on benthic filter feeders at least partly revealed a negative influence. However, it is still unclear whether the effects of microplastics differ from those of natural suspended microparticles, which constitute a common stressor in many coastal environments. We present a series of experiments that compared the effects of six-week exposures of marine mussels to two types of natural particles (red clay and diatom shells) to two types of plastic particles (Polymethyl Methacrylate and Polyvinyl Chloride). Mussels of the family Mytilidae from temperate regions (Japan, Chile, Tasmania) through subtropical (Israel) to tropical environments (Cabo Verde) were exposed to concentrations of 1.5 mg/L, 15 mg/L and 150 mg/L of the respective microparticles. At the end of this period, we found significant effects of suspended particles on respiration rate, byssus production and condition index of the animals. There was no significant effect on clearance rate and survival. Surprisingly, we observed only small differences between the effects of the different types of particles, which suggests that the mussels were generally equally robust towards exposure to variable concentrations of suspended solids regardless of whether they were natural or plastic. We conclude, that microplastics and suspended solids elicit similar effects on the tested response variables, and that both types of microparticles mainly cause acute responses rather than more persistent carry-over effects.

Development of a DNA Metabarcoding Method for the Identification of Bivalve Species in Seafood Products.

The production of bivalve species has been increasing in the last decades. In spite of strict requirements for species declaration, incorrect labelling of bivalve products has repeatedly been detected. We present a DNA metabarcoding method allowing the identification of bivalve species belonging to the bivalve families Mytilidae (mussels), Pectinidae (scallops), and Ostreidae (oysters) in foodstuffs. The method, developed on Illumina instruments, targets a 150 bp fragment of mitochondrial 16S rDNA. We designed seven primers (three primers for mussel species, two primers for scallop species and a primer pair for oyster species) and combined them in a triplex PCR assay. In each of eleven reference samples, the bivalve species was identified correctly. In ten DNA extract mixtures, not only the main component (97.0-98.0%) but also the minor components (0.5-1.5%) were detected correctly, with only a few exceptions. The DNA metabarcoding method was found to be applicable to complex and processed foodstuffs, allowing the identification of bivalves in, e.g., marinated form, in sauces, in seafood mixes and even in instant noodle seafood. The method is highly suitable for food authentication in routine analysis, in particular in combination with a DNA metabarcoding method for mammalian and poultry species published recently.

Biochemical and metabolic responses of the deep-sea mussel Bathymodiolus platifrons to cadmium and copper exposure.

Greater interest in commercial deep-sea mining has been accompanied by mounting environmental concerns, including metal contamination resulting from mining activities. However, little is known about the toxic effects of metal exposure on deep-sea life. Given its ability to accumulate metals from the surrounding environment, its wide distribution at both vents and seeps, and its high abundance, the deep-sea mussel Bathymodiolus platifrons could serve as an ideal model to investigate the toxicological responses of deep-sea organisms to metal exposure. Here, we evaluated metal accumulation, traditional metal-related biomarkers, namely acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase, catalase, reduced glutathione, metallothioneins, and malondialdehyde, as well as metabolic profiles in the gills of B. platifrons after a 7-day exposure to copper (100 µg/L), cadmium (500 µg/L), or copper-plus-cadmium treatments (100 µg/L Cu and 500 µg/L Cd). Metal exposure concentrations selected in this study can be found in deep-sea hydrothermal environments. Metal exposure resulted in significant metal accumulation in the gills of the mussel, indicating that B. platifrons has promise for use as an indicator of deep-sea metal pollution levels. Traditional biomarkers (AKP, ACP, and measured antioxidants) revealed cellular injury and oxidative stress in mussels following metal exposure. Metabolic responses in the three treatment groups indicated that metal exposure perturbed osmoregulation, energy metabolism, and nucleotide metabolism in mussels, in a response marked by differentially altered levels of amino acids, hypotaurine, betaine, succinate, glucose 6-phosphate, fructose 6-phosphate, guanosine, guanosine 5'-monophosphate, and inosine. Nevertheless, several uniquely altered metabolites were found in each treatment exposure group, suggesting dissimilar modes of toxicity between the two metal types. In the Cd-exposed group, the monosaccharide D-allose, which is involved in suppressing mitochondrial ROS production, was downregulated, a response consistent with oxidative stress in Cd-exposed B. platifrons. In the Cu-exposed group, the detected alterations in dopamine, dopamine-related, and serotonin-related metabolites together suggest disturbed neurotransmission in Cu-exposed B. platifrons. In the Cu-plus-Cd group, we detected a decline in fatty acid levels, implying that exposure to both metals jointly exerted a negative influence on the physiological functioning of the mussel. To the best of our knowledge, this is the first study to investigate changes in metabolite profiles in Bathymodiolus mussels exposed to metal. The findings reported here advance our understanding of the adverse impact of metal exposure on deep-sea life and can inform deep-sea mining assessments through the use of multiple biomarkers.

[Cell Function Research of ß-Trefoil Lectins from Mytilidae].

Two novel ß-trefoil lectins, MytiLec-1 and SeviL were found from mussels in the coast of Yokohama and Nagasaki. MytiLec-1 was purified from gill and mantle of Mytilus galloprovincialis. It was consisted of 149 amino acid residues and there was no similarity with any other proteins when it was discovered. We advocate for this "Mytilectin" as a new protein family because of their novelty of its primary structure and homologues were also found in other mussels. Glycan array analysis revealed that MytiLec-1 specifically bound to the Gb3 and Gb4 glycan which contained the α-galactoside. MytiLec-1 caused the apoptosis against the Burkitt's lymphoma cells through the interaction of Gb3 express in their cell surface. On the other hand, SeviL obtained from gill and mantle of Mytilisepta virgata showed the specific binding against GM1b, asialo GM1 and SSEA-4 which are known as glycosphingolipid glycan including the ß-galactoside. In addition, SeviL was identified as R type lectin by confirmation of QXW motif within its primary structure. Messenger RNA of SeviL like R type lectins was also found among the musssels including Mytilus galloprovincialis. SeviL also showed the apoptosis against asialo GM1 expressing cells. To apply the anticancer lectin as a novel molecular target drug, primary structure of MytiLec-1 was analyzed to enhance the stabilization of confirmation by computational design technique. It was succeeded to produce a monomeric artificial ß-trefoil lectin, Mitsuba-1 without losing the Gb3 binding ability. Comparison of biological function between Mitsuba-1 and MytiLec-1 is also described in this study.

Qualidade microbiológica da água e dos mexilhões Perna perna (Linnaeus, 1758) cultivados em Piúma, Espírito Santo, Brasil / Microbiological quality of water and Perna perna (Linnaeus, 1758) mussels cultivated in Piúma, Espírito Santo, Brazil

RESUMO Este estudo objetivou verificar a qualidade microbiológica da água e dos mexilhões cultivados pela Associação dos Maricultores de Piúma (AMPI), Espírito Santo, Brasil. Foram realizadas sete coletas de água e mexilhões, mensalmente, entre outubro de 2016 e maio de 2017. Os mexilhões foram coletados nos long lines da AMPI, e em cada mês foram coletados 40 mexilhões Perna perna e 100 mL de água do local. O material coletado foi destinado ao laboratório para a realização das análises microbiológicas em duplicata, número mais provável de coliformes totais (CT) e termotolerantes (Ctt), presença ou ausência de Salmonella sp e número de unidades formadoras de colônias de Staphylococcus aureus. Os resultados mostraram que o número de Ctt nas amostras de água no mês de janeiro estavam acima do permitido pela Resolução n° 357 do Conselho Nacional do Meio Ambiente (CONAMA). Já os níveis de Ctt e Staphylococcus aureus na carne dos mexilhões mostraram-se dentro do limite aceitável pela RDC n° 12 da Agência Nacional de Vigilância Sanitária (ANVISA). Entretanto, foram encontradas bactérias com características do gênero Salmonella sp nos meses de dezembro e março nos mexilhões, impossibilitando sua comercialização e seu consumo. Durante esses meses, a cidade tem alto fluxo de turistas. Por fim, recomenda-se a realização das análises microbiológicas continuamente, principalmente no período do verão, época que tem grande fluxo de turistas no município de Piúma e que registrou presença de Salmonella na carne dos mexilhões e níveis de Ctt na água acima do permitido pelas legislações vigentes.

ABSTRACT This study aimed to verify the microbiological quality of water and mussels cultivated by the Piúma Farmers Association (Associação dos Maricultores de Piúma — AMPI), Espírito Santo, Brazil. Seven samples of water and mussels were collected monthly from October 2016 to May 2017. The mussels were collected from the long lines of the AMPI, and in each month 40 mussels Perna perna and 100 mL of water were sampled from the site. The collected material was sent to the laboratory for duplicate microbiological analysis, Most Probable Number of Total (CT) and Thermotolerant (Ctt) coliforms, presence or absence of Salmonella sp and number of Staphylococcus aureus colony forming units. The results showed that the number of Ctt in the water samples in January was higher than that allowed by Resolution 357 of the National Environment Council (Conselho Nacional do Meio Ambiente — CONAMA). The levels of Ctt and Staphylococcus aureus in mussel meat were within the acceptable range by the Brazilian National Environment Council (Agência Nacional de Vigilância Sanitária — ANVISA) Resolution RDC No. 12. However, colonies with characteristics of Salmonella sp were found in December and March in the mussels, making it impossible to sell and consume. This period coincides with a high flow of tourists in the municipality. Finally, it is recommended to perform microbiological analyzes continuously, especially in the summer, where there are a lot of tourists in the city of Piúma, period that showed the presence of Salmonella in the meat of mussels and Ctt levels in water above the allowed current legislation.

Purification and Functional Characterization of the Effects on Cell Signaling of Mytilectin: A Novel ß-Trefoil Lectin from Marine Mussels.

In the 2010s, a novel lectin family with ß-trefoil folding has been identified in marine mussels from the family Mytilidae (phylum Mollusca). "MytiLec-1," the lectin described in this chapter, was the first member of this family to be isolated and characterized from the Mediterranean mussel Mytilus galloprovincialis, a commercially and ecologically important species, spread in marine coastal areas worldwide. MytiLec-1 bound to the sugar moiety of globotriose (Gb3: Galα1-4Galß1-4Glc), an α-galactoside, leading to apoptosis of Gb3-expressing Burkitt's lymphoma cells. Although the primary structure of MytiLec-1 was quite unusual, its three-dimensional structure was arranged as a ß-trefoil fold, which is the typical architecture of "Ricin B chain (or R)-type" lectins, which are found in a broad range of organisms. To date, MytiLec-1-like lectins have been exclusively found in a few species of the mollusk family Mytilidae (M. galloprovincialis, M. trossulus, M. californianus, and Crenomytilus grayanus) and in the phylum Brachiopoda. Transcriptome data revealed the presence of different structural forms of mytilectin in mussels, which included prototype and chimera-type proteins. The primary sequence of these lectins did not match any previously described known protein family, leading to their assignment to the new "mytilectin family." We here report the method of purification of this lectin and describe its use in cell biology.

The effects of cold stress on Mytilus species in the natural environment.

Environmental stressors induce changes in marine mussels from molecular (e.g., neurotransmitter and chaperone concentration, and expression of immune- and heat-shock protein-related genes) to physiological (e.g., filtration and heart rates, the number of circulating hemocytes) levels. Temperature directly affects the biogeographic distribution of mussels. Chaperones might form an essential part of endogenous protective mechanisms for the adaptation of these animals to low temperatures in nature. Here, we review the available studies dealing with cold stress responses of Mytilidae family members in their natural environment.

The filter-feeding bivalve Mytilus chilensis capture pelagic stages of Caligus rogercresseyi: A potential controller of the sea lice fish parasites.

The copepod Caligus rogercresseyi is an ectoparasite of several salmonid species. The pumping activity of filter-feeding molluscs could reduce the abundance of copepod dispersive larval stages in the water column. In this research, nauplius II and copepodid larvae of C. rogercresseyi were exposed to filtering mussels (Mytilus chilensis) of different sizes. These mussels were able to filter both larval stages, although they were more efficient in catching nauplius II. The fact that nauplius II were ingested more efficiently could be explained by their smaller size, lower swimming velocity (escape) and longer resting times between movements, when they were exposed to the influx of water around the inhalant area of the mussels. Larger mussels were more effective filtering C. rogercresseyi larvae due to their larger inhalant area and the related water influx. Additionally, the results suggest that larvae captured by the mussels can be incorporated into pseudofaeces or ingested and then released as part of the faeces. Thus, high concentrations of M. chilensis surrounding salmon farms may act as biological barriers, reducing the density of copepod dispersive larval stages and, thus, salmon infestations.

Metal adaptation strategies of deep-sea Bathymodiolus mussels from a cold seep and three hydrothermal vents in the West Pacific.

Deep-sea Bathymodiolus mussels are ubiquitous in most cold seeps and hydrothermal fields, where they have adapted to various toxic environments including high metal exposure. However, there is scarce knowledge of metal accumulation and metal-related biomarkers in B. mussels. Here, we present data for metal concentrations (Ag, Cd, Cr, Cu, Fe, Mn, Pb, and Zn) and metal related biomarkers (superoxide dismutase-SOD, catalase-CAT, glutathione peroxidase-GPX, glutathione-GSH, metallothioneins-MTs, and lipid peroxidation-LPO) in different tissues of B. mussels from four different deep-sea geochemical settings: one cold seep and three vent fields in the West Pacific Ocean. Results showed that mussel gills generally exhibited higher metal enrichment than the mantle. Mussels from hydrothermal vents usually had higher metal concentrations (Fe, Cr, Cd, and Pb) than those from cold seep, which could be related to their higher contents in fluids or sediments. However, despite quite different metals loads among the geochemical environment settings, Mn, Zn, and Cu concentrations varied over a smaller range across the sampling sites, implying biological regulation by deep-sea mussels for these elements. Several statistically significant correlations were observed between SOD, CAT, GSH, MTs, and metal levels in analyzed tissues. Although the vent ecosystem is harsher than the cold seep ecosystem, according to our results their mussels' biomarker levels were not so different. This finding suggests that some adaptive or compensatory mechanisms may occur in chronically polluted deep-sea mussels. Principal component analysis allowed for distinguishing different deep-sea settings, indicating that B. mussels are robust indicators of their living environments. We also compared our results with those reported for coastal mussels. To our best knowledge, this is the first integrated study to report metal accumulation and metal-related biomarkers in the deep-sea B. mussels from the West Pacific.

A mitochondrial genome phylogeny of Mytilidae (Bivalvia: Mytilida).

The family Mytilidae is a family of bivalve mussels that are distributed worldwide in diverse marine habitats. Within the family, classification systems and phylogenetic relationships among subfamilies remain not yet fully resolved. In this study, we newly determined 9 mitochondrial genome sequences from 7 subfamilies: Bathymodiolus thermophilus (Bathymodiolinae), Modiolus nipponicus (Modiolinae), Lithophaga curta (the first representative of Lithophaginae), Brachidontes mutabilis (Brachidontinae), Mytilisepta virgata (Brachidontinae), Mytilisepta keenae (Brachidontinae), Crenomytilus grayanus (Mytilinae), Gregariella coralliophaga (Crenellinae), and Septifer bilocularis (the first representative of Septiferinae). Phylogenetic trees using maximum likelihood and Bayesian inference methods for 28 mitochondrial genomes (including 19 previously published sequences) showed two major clades with high support values: Clade 1 ((Bathymodiolinae + Modiolinae) + (Lithophaginae + Limnoperninae)) and Clade 2 (((Mytilinae + Crenellinae) + Septiferinae) + Brachidontinae). The position of the genus Lithophaga (representing Lithophaginae) differed from a previously published molecular phylogeny. Divergence time analysis with a molecular clock indicated that lineage splitting among the major subfamilies of Mytilidae (including the habitat transition from marine to freshwater environments by ancestral Limnoperninae) occurred in the Mesozoic period, coinciding with high diversification rates of marine fauna during that time. This is the first mitochondrial genome-based phylogenetic study of the Mytilidae that covers nearly all subfamily members, excluding the subfamily Dacrydiinae.