RESUMEN
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.
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Adaptación Fisiológica , Variación Genética , Mytilus , Polimorfismo de Nucleótido Simple , Animales , Mytilus/genética , Mytilus/fisiología , Adaptación Fisiológica/genética , Genética de Población , Flujo GénicoRESUMEN
In late summer and early autumn 2022, an intense bloom of Protoceratium reticulatum-the main yessotoxin (YTX) producer along Chilean coasts and a major threat to artisanal fisheries, the aquaculture industry, and environmental health-was recorded in the Patagonian fjord system. The high YTX levels (>3.75 mg kg-1) resulted in the first ban of shellfish collection in Chile. At Puyuhuapi Fjord, a global "hotspot" of harmful algal bloom events, the cell density of P. reticulatum determined in integrated tube samples (0-10 m) at the end of April 2022 reached 407,000 cells L-1. At the same time, YTX levels well exceeded the regulatory limit by roughly 2.5-fold, with concentrations as high as 9.42 mg kg-1 measured in native populations of the blue mussel Mytilus chilensis. Five different YTX analogues, 45-OH-YTX, COOH-45-keto-YTX, COOH-45-OH-YTX, COOH-YTX, and 45,55-diOH-YTX, were also detected in relevant amounts. While the ban lasted close to 3 months, accumulation and detoxification processes were monitored over a 1-year period. This study assessed the implications of high levels of YTXs and their analogues on the local economy and ecosystem health, given the increase in P. reticulatum blooms predicted for NW Patagonia in the context of a changing climate.
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Monitoreo del Ambiente , Estuarios , Venenos de Moluscos , Oxocinas , Chile , Animales , Oxocinas/análisis , Floraciones de Algas Nocivas , Mytilus , Contaminantes Químicos del Agua/análisis , Toxinas Marinas/análisisRESUMEN
The increase in hypoxia events, a result of climate change in coastal and fjord ecosystems, impacts the health and survival of mussels. These organisms deploy physiological and molecular responses as an adaptive mechanism to maintain cellular homeostasis under environmental stress. However, the specific effects of hypoxia on mussels of socioeconomic interest, such as Mytilus chilensis, are unknown. Using RNA-seq, we investigated the transcriptomic profiles of the gills, digestive gland, and adductor muscle of M. chilensis under hypoxia (10 days at 2 mg L-1) and reoxygenation (10 days at 6 mg L-1). There were 15,056 differentially expressed transcripts identified in gills, 11,864 in the digestive gland, and 9862 in the adductor muscle. The response varied among tissues, showing chromosomal changes in Chr1, Chr9, and Chr10 during hypoxia. Hypoxia regulated signaling genes in the Toll-like, mTOR, citrate cycle, and apoptosis pathways in gills, indicating metabolic and immunological alterations. These changes suggest that hypoxia induced a metabolic shift in mussels, reducing reliance on aerobic respiration and increasing reliance on anaerobic metabolism. Furthermore, hypoxia appeared to suppress the immune response, potentially increasing disease susceptibility, with negative implications for the mussel culture industry and natural bed populations. This study provides pivotal insights into metabolic and immunological adaptations to hypoxia in M. chilensis, offering candidate genes for adaptive traits.
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Estrés del Retículo Endoplásmico , Branquias , Mytilus , Transcriptoma , Animales , Mytilus/genética , Branquias/metabolismo , Estrés del Retículo Endoplásmico/genética , Hipoxia/genética , Hipoxia/metabolismoRESUMEN
BACKGROUND: Disseminated neoplasia (DN) is a proliferative cell disorder of the circulatory system of bivalve mollusks. The disease is transmitted between individuals and can also be induced by external chemical agents such as bromodeoxyuridine. In Mya arenaria, we have cloned and characterized an LTR-retrotransposon named Steamer. Steamer mRNA levels and gene copy number correlates with DN and can be used as a marker of the disease. So far, the only mollusk where a retrotransposon expression relates to DN is Mya arenaria. On the other hand, it has been reported that the Chilean blue mussel Mytilus chilensis can also suffers DN. Our aim was to identify retrotransposons in Mytilus chilensis and to study their expression levels in the context of disseminated neoplasia. RESULTS: Here we show that 7.1% of individuals collected in August 2018, from two farming areas, presents morphological characteristics described in DN. Using Steamer sequence to interrogate the transcriptome of M. chilensis we found two putative retrotransposons, named Steamer-like elements (MchSLEs). MchSLEs are present in the genome of M. chilensis and MchSLE1 is indeed an LTR-retrotransposon. Neither expression, nor copy number of the reported MchSLEs correlate with DN status but both are expressed at different levels among individual animals. We also report that in cultured M. chilensis haemocytes MchSLEs1 expression can be induced by bromodeoxyuridine. CONCLUSIONS: We conclude that SLEs present in Mytilus chilensis are differentially expressed among individuals and do not correlate with disseminated neoplasia. Treatment of haemocytes with a stressor like bromodeoxyuridine induces expression of MchSLE1 suggesting that in Mytilus chilensis environmental stressors can induce activation of LTR-retrotransposon.
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Mytilus , Retroelementos , Animales , Mytilus/genética , Retroelementos/genética , ChileRESUMEN
LTR-retrotransposons are transposable elements characterized by the presence of long terminal repeats (LTRs) directly flanking an internal coding region. They share genome organization and replication strategies with retroviruses. Steamer-like Element-1 (MchSLE-1) is an LTR-retrotransposon identified in the genome of the Chilean blue mussel Mytilus chilensis. MchSLE-1 is transcribed; however, whether its RNA is also translated and the mechanism underlying such translation remain to be elucidated. Here, we characterize the MchSLE-1 translation mechanism. We found that the MchSLE-1 5' and 3'LTRs command transcription of sense and antisense RNAs, respectively. Using luciferase reporters commanded by the untranslated regions (UTRs) of MchSLE-1, we found that in vitro 5'UTR sense is unable to initiate translation, whereas the antisense 5'UTR initiates translation even when the eIF4E-eIF4G interaction was disrupted, suggesting the presence of an internal ribosomal entry site (IRES). The antisense 5'UTR IRES activity was tested using bicistronic reporters. The antisense 5'UTR has IRES activity only when the mRNA is transcribed in the nucleus, suggesting that nuclear RNA-binding proteins are required to modulate its activity. Indeed, heterogeneous nuclear ribonucleoprotein K (hnRNPK) was identified as an IRES trans-acting factor (ITAF) of the MchSLE-1 IRES. To our knowledge, this is the first report describing an IRES in an antisense mRNA derived from a mussel LTR-retrotransposon.
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Sitios Internos de Entrada al Ribosoma , Mytilus , Animales , ARN Mensajero/genética , ARN Mensajero/metabolismo , Sitios Internos de Entrada al Ribosoma/genética , Retroelementos/genética , Ribonucleoproteína Heterogénea-Nuclear Grupo K/genética , Ribonucleoproteína Heterogénea-Nuclear Grupo K/metabolismo , Regiones no Traducidas 5' , Mytilus/genética , Mytilus/metabolismo , Biosíntesis de ProteínasRESUMEN
The Southern Ocean and the Antarctic Circumpolar Current create environmental conditions that serve as an efficient barrier to prevent the colonization of non-native species (NNS) in the marine ecosystems of Antarctica. However, warming of the Southern Ocean and the increasing number of transport opportunities are reducing the physiological and physical barriers, increasing the chances of NNS arriving. The aim of this study was to determine the limits of survival of the juvenile mussels, M. chilensis, under current Antarctic conditions and those projected under climate change. These assessments were used to define the mussels potential for establishment in the Antarctic region. Experimental mussels were exposed to four treatments: -1.5 °C (Antarctic winter), 2 °C (Antarctic summer), 4 °C (Antarctic projected) and 8 °C (control) for 80 days and a combination of physiological and transcriptomics approaches were used to investigate mussel response. The molecular responses of mussels were congruent with the physiological results, revealing tolerance to Antarctic winter temperatures. However, a higher number of regulated differentially expressed gene (DEGs) were reported in mussels exposed to Antarctic winter temperatures (-1.5 °C). This tolerance was associated with the activation of the biological processes associated with apoptosis (up regulated) and both cell division and cilium assembly (down regulated). The reduced feeding rate and the negative scope for growth, for a large part of the exposure period at -1.5 °C, suggests that Antarctic winter temperatures represents an environmental barrier to M. chilensis from the Magellanic region settling in the Antarctic. Although M. chilensis are not robust to current Antarctica thermal conditions, future warming scenarios are likely to weaken these physiological barriers. These results strongly suggest that the West Antarctic Peninsula could become part of Mytilus distributional range, especially with dispersal aided by increasing maritime transport activity across the Southern Ocean.
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Mytilus , Agua de Mar , Animales , Mytilus/fisiología , Ecosistema , Temperatura , Regiones Antárticas , Océanos y MaresRESUMEN
This study assessed the concentrations of trace metals in tissues of Mytilus californianus from the west coast of Baja California, Mexico, during the cold and warm seasons. The concentrations of silver, cadmium, copper and zinc in mussel tissues were measured using Atomic Absorption Spectrophotometry. Silver concentrations ranged from 0.03 to 0.48 µg/g dry weight (d.w.) with significantly higher values registered at sites close to densely populated areas. Cadmium, copper, and zinc concentrations ranged from 0.57 to 7.83 µg/g d.w., 3.71 to 621 µg/g d.w., and 57.54 to 124.55 µg/g d.w., respectively. According to the WHO, values of copper and zinc were within acceptable limits. The maximum values of cadmium, however, exceeded the recommended limits set by the European Commission (2014). The human health risk of the metals analyzed was low (THQ and HI < 1). The regular monitoring of trace metals in M. californianus is recommended for a more definitive evaluation of contaminants.
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Mytilus , Oligoelementos , Humanos , Animales , México , Cobre , Cadmio , Plata , ZincRESUMEN
Hybrid zones among mussel species have been extensively studied in the northern hemisphere. In South America, it has only recently become possible to study the natural hybrid zones, due to the clarification of the taxonomy of native mussels of the Mytilus genus. Analysing 54 SNP markers, we show the genetic species composition and admixture in the hybrid zone between M. chilensis and M. platensis in the southern end of South America. Bayesian, non-Bayesian clustering and re-assignment algorithms showed that the natural hybrid zone between M. chilensis and M. platensis in the Strait of Magellan, Isla Grande de Tierra del Fuego and the Falkland Islands shows clinal architecture. The hybrid zone can be divided into three different areas: the first one is on the Atlantic coast where only pure M. platensis and hybrid were found. In the second one, inside the Strait of Magellan, pure individuals of both species and mussels with variable degrees of hybridisation coexist. In the last area at the Strait in front of Punta Arenas City, fjords on the Isla Grande de Tierra del Fuego, and at the Beagle Channel, only M. chilensis and a low number of hybrids were found. According to the proportion of hybrids, bays with protected conditions away from strong currents would give better conditions for hybridisation. We do not find evidence of any other mussel species such as M. edulis, M. galloprovincialis, M. planulatus or M. trossulus in the zone.
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Mytilus , Humanos , Animales , Perros , Mytilus/genética , Islas Malvinas , Teorema de Bayes , Genotipo , América del SurRESUMEN
The objective of this work was to discover a biochemical pathway to explain the transfer of cadmium, a toxic element, from seawater to cultured mussels. Understanding the intricacies of this transfer is crucial for global mussel crops, as it has the potential to mitigate risks to human health and prevent economic losses in the industry. We focused our investigation on Yal Bay, a typical area with intense mussel aquaculture activity (16,000 t y-1) in the inland sea of southern Chile. Seasonal samples of blue mussels (Mytilus chilensis) were collected and analyzed from September 2014 to December 2015 at two integrated depths (0-5 m and 5-10 m). Diurnal and nocturnal seston, seawater, benthic sediments and decanted suspensions from the water column were recorded. Our findings indicate that nocturnal seston satisfactorily explains the presence of cadmium in Mytilus chilensis aquaculture throughout its annual temporal distribution (Spearman rs = 0.63, p = 0.002).
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Mytilus edulis , Mytilus , Animales , Humanos , Mytilus/metabolismo , Cadmio/metabolismo , Acuicultura , Agua de MarRESUMEN
Eastern Boundary Upwelling Systems (EBUS) deliver cold, nutrient-rich waters, influencing coastal biota from the molecular to the ecosystem level. Although local upwelling (U) and downwelling (DU) conditions are often known, their influence on body attributes of relevant species has not been systematically compared within and between EBUS (i.e., below and above regional scales). Hence, we compared the physical-chemical characteristics of U and DU sites in the Humboldt Current system (Chile) and the Iberian Current system (Portugal). We then assessed the influence of U and DU upon eight body attributes in purple mussels (Perumytilus purpuratus) and Mediterranean mussels (Mytilus galloprovincialis), from the Humboldt and Iberian systems, respectively. We hypothesized that bivalves from U sites display better fitness, as measured by body attributes, regardless of their origin (EBUS). As expected, waters from U sites in both systems showed lower temperatures and pH, and higher nitrite concentrations. We also found that mussels from U sites showed better fitness than those in DU sites in 12 out of 16 direct U vs DU comparisons. Shell length, shell volume, organic content of soft-tissues, and mechanical properties of the shell averaged consistently higher in mussels from U sites in both Current systems. In addition, total weight, soft-tissue weight, shell weight and shell thickness were all higher in the U site at the Humboldt system but had less consistent differences at the Iberian system. Altogether, most results supported our working hypothesis and indicate that U conditions support better fitted mussels. The few attributes that did not exhibit the expected U vs DU differences in the Iberian system suggest that local and species-specific differences also play a role on the attributes of these species. These results may also serve as a reference point for further studies addressing the influence of upwelling in these productive, critically important systems.
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Ecosistema , Mytilus , Animales , Chile , PortugalRESUMEN
Marine mussels, especially Mytilus galloprovincialis, are well-established sentinel species, being naturally resistant to the exposure to multiple xenobiotics of natural and anthropogenic origin. Even if the response to multiple xenobiotic exposure is well known at the host level, the role of the mussel-associated microbiome in the animal response to environmental pollution is poorly explored, despite its potential in xenobiotic detoxification and its important role in host development, protection, and adaptation. Here, we characterized the microbiome-host integrative response of M. galloprovincialis in a real-world setting, involving exposure to a complex pattern of emerging pollutants, as occurs in the Northwestern Adriatic Sea. A total of 387 mussel individuals from 3 commercial farms, spanning about 200 km along the Northwestern Adriatic coast, and in 3 different seasons, were collected. Multiresidue analysis (for quantitative xenobiotic determination), transcriptomics (for host physiological response), and metagenomics (for host-associated microbial taxonomical and functional features) analyses were performed on the digestive glands. According to our findings, M. galloprovincialis responds to the presence of the complex pattern of multiple emerging pollutants - including the antibiotics sulfamethoxazole, erythromycin, and tetracycline, the herbicides atrazine and metolachlor, and the insecticide N,N-diethyl-m-toluamide - integrating host defense mechanisms, e.g., through upregulation of transcripts involved in animal metabolic activity, and microbiome-mediated detoxification functions, including microbial functionalities involved in multidrug or tetracycline resistance. Overall, our data highlight the importance of the mussel-associated microbiome as a strategic player for the orchestration of resistance to the multixenobiotic exposure at the holobiont level, providing strategic functionalities for the detoxification of multiple xenobiotic substances, as occurring in real world exposure settings. Complementing the host with microbiome-dependent xenobiotic degradative and resistance genes, the M. galloprovincialis digestive gland associated microbiome can have an important role in the detoxification of emerging pollutants in a context of high anthropogenic pressure, supporting the relevance of mussel systems as potential animal-based bioremediation tool.
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Microbiota , Mytilus , Plaguicidas , Contaminantes Químicos del Agua , Animales , Mytilus/metabolismo , Estaciones del Año , Plaguicidas/análisis , Xenobióticos/metabolismo , Contaminantes Químicos del Agua/análisisRESUMEN
Pinnatoxins (PnTXs) produced by the cosmopolitan dinoflagellate Vulcanodinium rugosum are highly potent cyclic imines that represent a risk for seafood consumers, artisanal fisheries, and the local aquaculture industry. Among the eight known PnTXs, pinnatoxin-G (PnTX-G) is the most frequent toxin analog detected in shellfish. Despite PnTX-G is still not internationally regulated, the French Agency for Food, Environmental and Occupational Health and Safety established that a risk for human consumers may exist when the accumulation of PnTX-G in shellfish exceeds 23 µg kg-1. This study reports the first detection of these fast-acting lipophilic toxins in localized shellfish banks (Mytilus chilensis) from the Chilean coast. Among 32 sentinel sampling stations monthly monitored for phytotoxins detection and quantification between 2021 and 2022 along the southern Chilean coast (from 36°25' S to 54°57'S), PnTx-G was only detected in shellfish from the southernmost region of Magallanes in concentrations that ranged between 15 and 100 µg kg-1, highlighting the binational (Chile/Argentina) Beagle Channel as a 'hotspot'. As Chile is one of the major mussel producers worldwide, this result raises concern about the potential adverse effect of PnTXs for human health and point to the need of governmental actions for an enhanced monitoring of these emerging toxins. To date, the production of PnTXs has not yet been associated with any microalgae species in Chilean waters.
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Dinoflagelados , Mytilus , Toxinas Biológicas , Perros , Humanos , Animales , Chile , Iminas/farmacología , Mariscos , Alimentos MarinosRESUMEN
The blue mussel Mytilus chilensis is an endemic and key socioeconomic species inhabiting the southern coast of Chile. This bivalve species supports a booming aquaculture industry, which entirely relies on artificially collected seeds from natural beds that are translocated to diverse physical-chemical ocean farming conditions. Furthermore, mussel production is threatened by a broad range of microorganisms, pollution, and environmental stressors that eventually impact its survival and growth. Herein, understanding the genomic basis of the local adaption is pivotal to developing sustainable shellfish aquaculture. We present a high-quality reference genome of M. chilensis, which is the first chromosome-level genome for a Mytilidae member in South America. The assembled genome size was 1.93 Gb, with a contig N50 of 134 Mb. Through Hi-C proximity ligation, 11,868 contigs were clustered, ordered, and assembled into 14 chromosomes in congruence with the karyological evidence. The M. chilensis genome comprises 34,530 genes and 4795 non-coding RNAs. A total of 57% of the genome contains repetitive sequences with predominancy of LTR-retrotransposons and unknown elements. Comparative genome analysis of M. chilensis and M. coruscus was conducted, revealing genic rearrangements distributed into the whole genome. Notably, transposable Steamer-like elements associated with horizontal transmissible cancer were explored in reference genomes, suggesting putative relationships at the chromosome level in Bivalvia. Genome expression analysis was also conducted, showing putative genomic differences between two ecologically different mussel populations. The evidence suggests that local genome adaptation and physiological plasticity can be analyzed to develop sustainable mussel production. The genome of M. chilensis provides pivotal molecular knowledge for the Mytilus complex.
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Mytilus edulis , Mytilus , Animales , Mytilus/genética , Chile , Acuicultura , Cromosomas/genéticaRESUMEN
Phylogeography often focuses on the spatial dimension of genetic diversity, rarely including the temporal dynamics occurring interannually among local populations, which can provide insight into past variations in reproductive success. Currently, there is an intense aquaculture industry of Mytilus spp. on the Southeast Pacific Coast which depends entirely on the spat released by natural populations forming a relevant and sensitive social-ecological system. Temporal and spatial spat variability from natural mussel beds could be related to interannual reproductive dynamics with variable reproductive success and recruitment, which leave genetic signatures. Temporal and spatial genetic structure was evaluated in six natural beds in the Southeast Pacific (from 39°25'S to 43°07'S) on the most abundant and widespread Mytilus lineage detected, Mytilus cf. chilensis, in 4 consecutive years. Analyses included data from >180 individuals per year, with a total of 751 (mitochondrial COI) and 747 (nuclear H1) individuals, respectively. Overall, both markers showed high haplotype diversity and low spatial and temporal genetic differentiation. Likely, the high dispersal capacity of Mytilus cf. chilensis maintains population homogeneity and prevents diversity erosion. The slight differences in genetic variance of COI were better explained by differences among sites (space), and conversely, the H1 genetic variance was better explained by interannual (temporal) comparisons, which could explain temporal variability in spat availability. This study highlights the important insights achieved with the evaluation of both temporal and spatial population genetic structures in marine species with high reproductive output, which can condition the success and sustainability of the relevant social-ecological system.
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Variación Genética , Mytilus , Humanos , Animales , Filogeografía , Acuicultura , Haplotipos , Mytilus/genéticaRESUMEN
Oysters and blue mussels are important hydrobiological resources for aquaculture. In Chile, they are farming on the Chiloé island, where around 18% of the world's mussels are produced, however, their nutritional dynamics are largely unknown. For this reason, the objective of this study was to determine the proximal biochemical composition and the fatty acid profile in the Chilean oyster (Ostrea chilensis), the Pacific oyster (Crassostrea gigas) and the Chilean mussel (Mytilus chilensis), to perform an intra and interspecific comparison. Shellfish sampled in winter were characterized by a high protein content, followed by medium values for lipid content and a low carbohydrate content compared to similar species in Europe. Also, oysters and mussels were found to be rich in omega-3 long chain polyunsaturated fatty acid (n-3 LC-PUFA), so they can be considered excellent functional food option for a healthy human diet. Their high contribution of n-3 LC-PUFA ranged between 5.2-12.9 µg FA mg-1 dry weight with high n-3/n-6 ratios, which depends on both the species and the on-growing location. Both taxa can be considered a plausible option to promote a healthy diet of marine origin in future generations. Also, these results could benefit the projection and development of aquaculture of these mollusks.
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Bivalvos , Crassostrea , Mytilus , Ostrea , Animales , Bivalvos/química , Chile , Ácidos Grasos , HumanosRESUMEN
We assessed the adaptive contribution of the mitochondrial genes involved with the respiratory chain and oxidative phosphorylation of the blue mussel Mytilus chilensis, a native and heavily exploited species in the inner sea of Chiloé Island, southern Chile. The assembled mitochondrial transcriptome of individuals from two ecologically different farm-impacted natural seedbeds, Cochamó (41°S) and Yaldad (42°S), represented about 4.5% of the whole de novo transcriptome of the species and showed location and tissue (gills, mantle) specific expression differences in 13 protein-coding mitochondrial genes. The RNA-Seq analysis detected differences in the number of up-regulated mitogenes between individuals from Cochamó (7) and Yaldad (11), some being tissue-specific (ND4L and COX2). However, the analysis did not detect transcripts-per-million (TPM = 0) of ND2 and ND5 in gills and ATP6 in mantle samples from Cochamó. Likewise, for ND6 and ATP8 in any sample. Several monomorphic location-specific mitochondrial genetic variants were detected in samples from Cochamó (78) and Yaldad (207), representing standing genetic variability to optimize mitochondrial functioning under local habitats. Overall, these mitochondrial transcriptomic differences reflect the impact of environmental conditions on the mitochondrial genome functioning and offer new markers to assess the effects on mussel fitness of habitat translocations, a routine industry practice. Likewise, these mitochondrial markers should help monitor and maintain adaptive population differences in this keystone and heavily exploited native species.
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Genoma Mitocondrial , Mytilus , Animales , Branquias , Humanos , Mytilus/genética , RNA-Seq , TranscriptomaRESUMEN
Chilean aquaculture mainly produces salmonids and molluscs. Salmonid production has been questioned by its excessive use of antimicrobials. This study aimed to investigate the bacterial microbiota composition of Mytilus spp. cultivated near salmonid farms and to determine the minimum inhibitory concentration (MIC) to florfenicol and oxytetracycline of its culturable bacteria. Seven Mytilus farming sites classified according to their proximity to salmon farms as close (CSF) or distant (DSF) were sampled in two years. We analyzed Mytilus microbiota composition through culture-independent methods, and isolated culturable bacteria, and identified those isolates with MIC values ≥ 64 µg mL-1 to florfenicol or oxytetracycline. Results revealed that the alpha diversity was affected by sampling year but not by Mytilus farming site location or its interaction. Nevertheless, in 2018, we observed a significant negative correlation between the alpha diversity of Mytilus microbiota in each farm sites and the tonnes of florfenicol reported for each phytosanitary management area. We detected significant differences in beta diversity and relative abundance of specific bacterial taxa in Mytilus microbiota depending on the proximity to salmon farms and years. A higher proportion of isolates with MIC values ≥ 64 µg mL-1 to both antibiotics was detected in 2019 compared to 2018, but not significant differences were detected according to Mytilus farming site location. However, in 2019, isolates from CSF sites showed higher MIC values for both antibiotics than those from DSF. Bacterial genera corresponding to isolates with MIC values ≥ 64 µg mL-1 represented a low proportion of Mytilus microbiota identified with the culture-independent approach, reflecting the need to implement new methodologies in the study of antimicrobial resistance. These results suggest that the proximity to salmonid farms and sampling year influence the Mytilus microbiota and MIC values of their bacterial isolates; however, other environmental variables should be considered in further studies.
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Microbiota , Mytilus , Oxitetraciclina , Animales , Antibacterianos/farmacología , Acuicultura , Pruebas de Sensibilidad Microbiana , Salmón , Tianfenicol/análogos & derivadosRESUMEN
The aim of this review was to identify the current knowledge regarding the concentration of microplastics in bivalves in the marine, estuarine, and freshwater environments. For this purpose, researches were conducted from September 2020 to February 2021 in the Scopus, Web of Science, and Google scholar databases, following a meticulous selection of articles. To comprehensively understand the selected articles, an extensive review was carried out in order to identify the methodologies employed, sampling sites, species evaluated, characteristics of the microplastics (concentrations, shapes, sizes, and polymers) and their relationship with the concentration of this particles in the environment. A total of 93 articles were selected, with an exponential growth in the number of articles from April 2014 to February 2021. Worldwide, 80 articles were realized in the Northern Hemisphere and thirteen in the Southern Hemisphere. The samplings of organisms were carried out in 36 countries, besides one in Antarctica. The concentration of microplastics were studied in 70 species, with mussels Mytilus spp. and the oysters Crassostrea spp. being the main genus studied. Due to the different methodologies used to digest the tissues of organisms and identify microplastics and species, it is difficult to make comparisons between the results of different studies. In addition, data on the concentrations of microplastics in the environment, as well as their composition and characteristics, are needed, enabling the verification of relationships with the concentrations identified in organisms, which does not occur in most studies. Thus, we suggest an increase in the number of studies to be realized in the southern hemisphere, future studies use the same methodology of digestion, the polymer identification of microplastics and samplings of the surrounding environment, enabling a greater comparison between studies.
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Mytilus , Contaminantes Químicos del Agua , Animales , Monitoreo del Ambiente , Microplásticos , Plásticos , Contaminantes Químicos del Agua/análisisRESUMEN
Pressures from anthropogenic activities are causing degradation of estuarine and coastal ecosystems around the world. Trace metals are key pollutants that are released and can partition in a range of environmental compartments, to be ultimately accumulated in exposed biota. The level of pressure varies with locations and the range and intensity of anthropogenic activities. The present study measured residues of trace metals in Mytilus mussel species collected from a range of locations around the world in areas experiencing a gradient of anthropogenic pressures that we classified as low, moderate, or high impact. The data showed no grouping/impact level when sampling sites in all countries were incorporated in the analysis, but there was significant clustering/impact level for most countries. Overall, high-impact areas were characterized by elevated concentrations of zinc, lead, nickel, and arsenic, whereas copper and silver were detected at higher concentrations in medium-impact areas. Finally, whereas most metals were found at lower concentrations in areas classified as low impact, cadmium was typically elevated in these areas. The present study provides a unique snapshot of worldwide levels of coastal metal contamination through the use of Mytilus species, a well-established marine biomonitoring tool. Environ Toxicol Chem 2021;40:3434-3440. © 2021 SETAC.
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Metales Pesados , Mytilus , Oligoelementos , Contaminantes Químicos del Agua , Animales , Ecosistema , Monitoreo del Ambiente , Metales Pesados/análisis , Mytilus/metabolismo , Oligoelementos/análisis , Contaminantes Químicos del Agua/análisisRESUMEN
We analyzed spatial and temporal variations in total mercury concentration (THg) in Mytilus californianus from the west coast of Baja California, México, and assessed the potential risk for human health. The sites from the northern zone showed the highest levels of THg over the entire three years of study, however, no significant differences among years were found. The highest level of THg (0.110 µg/g d.w.) was recorded in 2010 at Bajamar (SS2), and the lowest (0.011 µg/g d.w.) in 2007 and 2008 at Eréndira (SS4) and Los Ojitos (SS7), respectively. The estimated daily intake (EDI) values for adults through mussel consumption were lower than the oral reference dose (RfDo) and the acceptable daily intake (ADI) values established by the USEPA and the FAO/WHO, respectively. The target hazard quotient (THQ) values were <1.0, indicating that mercury concentrations in M. californianus are not likely to pose a risk for human health.