Bivalve Molluscs Research Articles

Determination of tetrodotoxin in bivalve mollusks by hydrophilic interaction liquid chromatography-triple quadrupole mass spectrometry with internal standard calibration and its contamination in Zhejiang province, China

A method was established for determining tetrodotoxin (TTX) in bivalve mollusks by hydrophilic interaction liquid chromatography-triple quadrupole mass spectrometry (HILIC-MS/MS) using kasugamycin as the internal standard for quantification. Samples were subjected to ultrasonic extraction with methanol–water (1:1, v/v) containing 0.5% acetic acid, protein precipitation with acetonitrile, clean-up using a cation exchange solid phase extraction cartridge, elution with acetonitrile:water (1:1, v/v) containing 0.3% hydrochloric acid, neutralization with ammonia before HILIC-MS/MS analysis. The average recovery of the samples spiked at 3 levels ranged in 84.6%-98.1% with the relative standard deviation less than 7.2%. Using this method, the contamination of TTX in 429 bivalve mollusk samples collected in the local markets during 2018 and 2020 was investigated. The detection rates were 12.0–18.8%, following the order of oyster > mussel > clam > scallop. High contaminated oysters and mussels with TTX were found in July to August. Moreover, TTX analogs found in bivalve mollusks included 4-epiTTX, 5,6,11-trideoxyTTX, 4,9-anhydroTTX, and 5-deoxyTTX/11-deoxyTTX.

Cellular and oxidative stress responses of Mytilus galloprovincialis to chlorpromazine: implications of an antipsychotic drug exposure study.

Introduction: Bivalve molluscs like Mytilus galloprovincialis are valuable bioindicators due to their filter-feeding lifestyle, wide distribution, and ability to concentrate xenobiotics. Studying the effects of pharmaceuticals on these molluscs is crucial given their presence in surface waters. This study investigated the response of M. galloprovincialis to chlorpromazine (Cpz), an antipsychotic with antiviral activity against influenza, HIV, and coronaviruses in human cells. Methods: In this study, we examined the 14-day impact of chlorpromazine (Cpz) on the model species M. galloprovincialis at two concentrations (Cpz 1: 12ng L-1 or 37 pM; Cpz 2: 12µg L-1 or 37nM). To ensure controlled exposure, a stock solution of Cpz was prepared and introduced into the tanks to match the intended concentrations. Seawater and stock solutions were refreshed every 48h. The primary focus of this study centered on evaluating cell viability, cell volume regulation, and oxidative stress indicators. Results: Although cell volume regulation, as assessed by decreasing regulatory volume Regulation volume decrease, did not show statistically significant changes during the experiment, digestive cell viability, on the other hand, showed a significant decrease (p < 0.01) in the Cpz 2 group, suggesting effects on the general health and survival of these cells. Biochemically, in both Cpz 1 and Cpz 2, superoxide dismutase activity increased, while catalase (CAT) decreased, causing an elevated lipid peroxidation thiobarbituric acid-reactive substances and protein carbonyls, particularly in the Cpz 2 group. The level of reduced glutathione (GSH) increased in both exposures, whereas the level of GSSG increased only in the Cpz 1 group. Consequently, the GSH/GSSG ratio was elevated in the Cpz 2 group only. Discussion: A comparison of the magnitudes of anti- and pro-oxidative manifestations indicated a pro-oxidative shift in both exposures. These findings show that Cpz induces non-specific symptoms of biochemical and cellular disturbances in M. galloprovincialis even at the low picomolar concentration.

Plasma β-1,3 Glucan Binding Protein Mediated Opsono-Phagocytosis by Hemocytes In Vitro of Marine Mussel Perna viridis.

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.

Environmental Assessment with Cage Exposure in the Neva Estuary, Baltic Sea: Metal Bioaccumulation and Physiologic Activity of Bivalve Molluscs

The rise in anthropogenic impacts on the marine environment requires new water management. The use of a triadic approach (bioaccumulation, bioassay, and physiological biomarkers) has been shown to have good applicability for the comparative assessment of the environmental state of the Neva Estuary (Gulf of Finland, Baltic Sea). The novelty of the methodological approach of the study was that it involved both active and passive bio-monitoring methods for assessing the quality of estuarine environment. The classical analyses of metal concentration in bottom sediments, in field biota (fish and molluscs), and in caged molluscs were accompanied by a bioassay of sediment toxicity using amphipods. The physiological state of molluscs kept in cages was assessed according to two functional characteristics, such as cardio-tolerance and metabolic activity (oxygen consumption rate), after exposition in cages. The method of active monitoring (caging exposure with molluscs) as a measurement of parameters in clean molluscs has proven itself well in controlling the accumulation of both metals and oil products. Macroalgae that are abundant in estuarine ecosystems are also good indicators of metals, at least showing the transition from bottom sediments to the next level of food webs. Unionid molluscs were found to be a more sensitive and effective indicator of contaminant accumulation than dreissenid molluscs, characterized by a low tolerance to changeable environmental conditions in the estuarine ecosystem and rather high mortality in cages. Our results have shown that caging exposure with unionids can be a widely used methodological approach for the assessment of estuarine environmental quality through the determination of metal concentrations in molluscs and their physiological state.

First application of a droplet digital PCR to detect Toxoplasma gondii in mussels.

Toxoplasmosis, caused by the protozoan Toxoplasma gondii, is one of the main food-, water- and soil-borne zoonotic disease worldwide. Over the past 20 years many papers were published on the transmission of T. gondii by marine animals, including mollusks, which can concentrate the oocysts and release them. Sporulated oocysts may remain viable and infective for 18 months in seawater. Therefore, raw or undercooked bivalve mollusks pose a risk to humans. This study aimed to apply and validate for the first time a very sensitive digital droplet polymerase chain reaction (ddPCR) protocol to detect and quantify T. gondii DNA in mussels. Four concentration levels: 8000 genomic copies (gc)/μL, 800 gc/μL, 80 gc/μL, 8 gc/μL of a T. gondii reference DNA were tested. DNA was extracted from 80 pools of mussels (Mytilus galloprovincialis). Forty pools were contaminated with T. gondii reference DNA and used as positive controls, while 40 pools were used as negative controls. DdPCR reaction was prepared using a protocol, previously developed by the authors, for detection of T. gondii in meat. Amplification was obtained up 8 gc/μL. All infected replicates resulted positive, as well as no droplets were detected in negative controls. The droplets produced in the reaction ranged from 8,828 to 14,075 (average 12,627 droplets). The sensitivity and specificity of ddPCR were 100% (95%CI = 94.3-99.9). In addition, 100 pools of mussels collected in the Gulf of Naples were used to validate the protocol. Of these 16% were positive (95% CI = 9.7-25.0) for T. gondii. Samples were also tested by real-time PCR and no positive samples were found. Data obtained from ddPCR showed good identification of negative and positive samples with higher specificity and efficiency than real-time PCR. This tool could be very useful for a rapid sensitive detection of low DNA concentrations of T. gondii in mussels, reducing the risk of toxoplasmosis in humans.

Valve gaping behaviour in the European oyster (Ostrea edulis) in response to changes in light intensity when combined with variations in salinity and seawater temperature

Valve gaping behaviour in bivalve molluscs controls the flow of water across gills that provides both food, and oxygen for respiration. Closure of the valves also provides protection from predators and poor-quality water conditions. Research presented here used a flow through seawater system with controlled changes in salinity and temperature, combined with continuous measurement of valve gape using Hall effect sensors, to study how changes in these variables affect the valve movements of the European oyster (Ostrea edulis) held under controlled long day-length conditions. A clear relationship between periods of reduced light intensity and maximum valve gape was recognised in preliminary studies and provided a benchmark against which to compare how changes in environmental conditions linked to climate change may alter the behaviour of these coastal marine bivalves. Oysters collected from the southwest coast of Norway in August 2022 were held for 72 h at full seawater salinity of 33.6 and a temperature of 15.8 ± 0.5 °C prior to exposure to a reduction in salinity down to 18.2 over a 3 h period. Oysters showed an initial reduction in valve gape width as salinity reached 31.4, with valve gape decreasing further as salinity fell to 28.8. All valves were fully closed at salinity 20.5. Oysters remained in this condition throughout the subsequent 21 h exposure period with salinity at 18.2. Thereafter salinity was increased in 3 steps. In the first step, salinity reached 24.2 over 2 h, and was held there over the following 22 h. All oysters commenced re-opening valves between salinity 22.8 and 24.2. When salinity was further increased to 27.3 over the subsequent 24 h, oysters returned to approximately their pre-exposure valve gape widths. When salinity 33.8 was delivered to the tanks there were 2 d during which maximum valve gape was significantly reduced, after which valve gape width returned to a pre-exposure condition. The predicted pattern of valve opening during reduced light intensity periods was maintained when seawater temperature was raised from 15.8 °C up to 20.1 °C in approximately 1 °C steps every 24 h. However, reduction of temperature from 20.1 °C in similar sized increments altered the expected patterns of behaviour. The results indicate that increasing occurrences of fluxes in salinity and temperature due to climate change have the potential to disrupt normal valve gaping behaviour in European oysters, creating an additional challenge to those they already face from invasive species and disease.

SIZE AND WEIGHT CHARACTERISTICS OF THE BIVALVE MOLLUSC ANADARA KAGOSHIMENSIS (TOKUNAGA, 1906) - THE ALIEN SPECIES IN THE SEA OF AZOV

For the first time the research focuses on studying the size and weight characteristics of the alien species in the Sea of Azov - bivalve mollusc Anadara kagoshimensis (Tokunaga, 1906). The relationship between allometric parameters of the mollusc (size and weight) were approximated by the power function. The maximal coefficient of determination is found for the power dependence of the total weight of the anadara on the width of the shell, with minimum coefficient of determination depending on the height of the shell. The maximum coefficient of determination is obtained for the power dependence of the raw weight of soft tissues of anadara on the length of its shell, with the minimum coefficient of determination depending on the width of the shell. The ratio of dry and raw weight of soft tissues is 0.16. Under comparison of the different environmental areas of anadara in the Black, Aenean seas and the Sea of Azov, the hatchery housing of mollusks in waters with moderate salinity is found to be the most favorable condition for their maximal growth.

ADAPTATION OF ANADARA KAGOSHIMENSIS (TOKUNAGA, 1906) TO HYPO- AND HYPEROSMOTIC ENVIRONMENTAL CONDITIONS: HEMOCYTE RESPONSE

Anadara kagoshimensis (Tokunaga, 1906) is an invasive species that has successfully colonized the waters of the Black Sea and the sea of Azov, despite the significantly lower salinity level of these waters in comparison with the native region. The morphological and morphometric characteristics of bivalve mollusk A. kagoshimensis erythrocytes were analyzed by light microscopy during adaptation to hypo- and hyperosmotic experimental conditions. The control group of mollusks was kept at 18‰ salinity. Experimental groups were acclimated to 8, 14, 35 and 45‰ salinity. A decrease of salinity was achieved by diluting seawater with distilled water at a rate of 1.5±0.5‰ per day. Sea salt was added to each aquarium to increase salinity. Salinity was increased at a rate of 2.5±0.5‰ per day. Exposure period was 2 days. It has been shown that the salinity range of 14-35‰ is natural for ark clam. No significant changes in cell morphology were observed under these conditions. At the same time, environmental salinity levels of 8 and 45‰ caused obvious stress: cellular anomalies appeared, and the linear characteristics of erythrocytes were changed. However, cell lysis did not occur, the values of the specific surface area and nuclear-cytoplasmic ratio did not change. The results of the present work indicate the ability of the arc clam to exist for some time in regions with extremely low and high salinity of the aquatic environment.

Quantification and valuation of the potential of shellfish ecosystem services in mitigating coastal eutrophication

Eutrophication of coastal waters due to anthropogenic nutrient enrichment is a significant problem in European seas and worldwide. Bivalve shellfish remove nutrients from the water through filtration of suspended particles. This ‘bioextraction’ capacity is a key regulating ecosystem service that contributes to eutrophication control, but the extent and value of this ecosystem service has not been well established. This study aims to assess the potential of shellfish ecosystem services in mitigating coastal eutrophication in European coastal waters. The estimation of the amount of nutrients removed by different bivalve species under specific culture practices and locations is relevant due to the variety, geographical distribution, and scale at which shellfish species are farmed in Europe.The approach used here consisted of (a) estimation of nutrient loading to European regional seas, and source apportionment where possible; (b) evaluation of nutrient removal by key species of bivalve shellfish; (c) analysis of the role of shellfish in top-down control of eutrophication as a complement to the established bottom-up approach of emissions reduction.The nitrogen removal capacity of bivalves was assessed using two complementary approaches: (i) elemental analysis of N concentration in soft tissues and shell; and (ii) modelling the physiology of shellfish at the typical farm. In both cases, the results were upscaled to the shellfish aquaculture production in Western Europe.Our results show that European shellfish aquaculture can help reduce negative water quality impacts of excess nutrients (nitrogen and phosphorus) in coastal communities. Different shellfish species have different removal rates, which can also be influenced by environmental conditions at the distinct locations and culture practices. The species responsible for the largest N removal (3356–3491 tonnes y−1) was the Mediterranean mussel (accounting for 53–70% of the total) which is also the farmed species with highest production in Europe. Our study shows that the EU annual current production of over half a million metric tonnes of bivalves removes between 4.8 and 6.5 kilotonnes of N per year. The annual cost of removing the same amount of nutrients using other measures would be between 15.9 and 21.6 billion €. This ecosystem service has not been used in Europe as part of a nutrient management framework. The results of this study aim to provide the basis for strategic guidelines to include shellfish aquaculture in watershed-scale nutrient management policies in the EU, following the same principles as the on-going programmes in the United States.

Quantitative Polymerase Chain Reaction for the estimation of toxigenic microalgae abundance in shellfish production waters

Certain species of marine microalgae produce potent biotoxins that pose a risk to human health if contaminated seafood is consumed, particularly filter feeding bivalve shellfish. In regions where this is likely to occur water and seafood produce are regularly monitored for the presence of harmful algal cells and their associated toxins, but the current approach is flawed by a lengthy delay before results are available to local authorities. Quantitative Polymerase Chain Reaction (qPCR) can be used to measure phytoplankton DNA sequences in a shorter timeframe, however it is not currently used in official testing practices. In this study, samples were collected almost weekly over six months from three sites within a known HAB hotspot, St Austell Bay in Cornwall, England. The abundance of algal cells in water was measured using microscopy and qPCR, and lipophilic toxins were quantified in mussel flesh using LC-MS/MS, focusing on the okadaic acid group. An increase in algal cell abundance occurred alongside an increase in the concentration of okadaic acid group toxins in mussel tissue at all three study sites, during September and October 2021. This event corresponded to an increase in the measured levels of Dinophysis accuminata DNA, measured using qPCR. In the following spring, the qPCR detected an increase in D. accuminata DNA levels in water samples, which was not detected by microscopy. Harmful algal species belonging to Alexandrium spp. and Pseudo-nitzschia spp. were also measured using qPCR, finding a similar increase in abundance in Autumn and Spring. The results are discussed with consideration of the potential merits and limitations of the qPCR technique versus conventional microscopy analysis, and its potential future role in phytoplankton surveillance under the Official Controls Regulations pertaining to shellfish.

Clam calamity: five concurrent cases of neurotoxic shellfish poisoning with varying presentations following ingestion of clams from Gulf of Mexico water contaminated with Karenia brevis confirmed by serum brevetoxin assays

Introduction Karinia brevis, a marine dinoflagellate, is the causative organism for “red-tide” on the east coast of Florida.This microbe produces brevetoxins, which bioaccumulate in filter feeding bivalve shellfish. In humans, inhalational exposure is common, while ingestion of contaminated shellfish is more rare. Ingested brevetoxin causes gastrointestinal and neurological symptoms collectively known as neurotoxic shellfish poisoning. Case cluster A group of tourists collected clams from a beach during a red tide event. The clams were soaked in brine, microwaved, and consumed for lunch. The index patient experienced seizure-like activity postprandially prompting the cohort to present for medical attention. Five people presented to the emergency department with neurotoxic shellfish poisoning-related symptoms. All patients received supportive care only. Symptoms resolved within 24 hours. Serum brevetoxin concentrations were reported for four patients. Discussion Ingestion of brevetoxin is rare but may become more common as the frequency and severity of “red-tide” events increase. In our cluster, each person consumed a different number of clams and presented with classic and some “non-classic” symptoms. A trend toward more severe symptoms with a larger number of clams ingested was observed. Conclusions This case cluster describes the clinical course of individuals after consumption of brevetoxin contaminated shellfish.

Toward better monitoring of human noroviruses and F-specific RNA bacteriophages in aquatic environments using bivalve mollusks and passive samplers: A case study.

Monitoring pathogenic enteric viruses in continental and marine water bodies is essential to control the viral contamination of human populations. Human Noroviruses (NoV) are the main enteric viruses present in surface waters and foodstuff. In a context of global change, it is currently a challenge to improve the management of viral pollutions in aquatic environments and thereby limit the contamination of vulnerable water bodies or foodstuffs. The aim of this study is to evaluate the potential of specific accumulation systems for improving the detection of NoV in water bodies, compared to direct water analyses. Passive samplers (Zetapor filters) and three species of bivalve molluscan shellfish (BMS) (Dreissena polymorpha, Mytilus edulis and Crassostreas gigas) were used as accumulation systems to determine their performance in monitoring continental and marine waters for viruses. F-specific RNA bacteriophages (FRNAPH) were also analyzed since they are described as indicators of NoV hazard in many studies. During a one-year study in a specific area frequently affected by fecal pollution, twelve campaigns of exposure of passive samplers and BMS in continental and coastal waters were conducted. Using suitable methods, NoV (genome) and FRNAPH (infectious and genome) were detected in these accumulation systems and in water at the same time points to determine the frequency of detection but also to gain a better understanding of viral pollution in this area. The reliability of FRNAPH as a NoV indicator was also investigated. Our results clearly showed that BMS were significantly better than passive samplers and direct water analyses for monitoring NoV and FRNAPH contamination in water bodies. A dilution of viral pollution between the continental and the coastal area was observed and can be explained by the distance from the source of the pollution. Viral pollution is clearly greater during the winter period, and stakeholders should take this into consideration in their attempts to limit the contamination of food and water. A significant correlation was once again shown between NoV and FRNAPH genomes in BMS, confirming the reliability of FRNAPH as a NoV indicator. Moreover, a strong correlation was observed between NoV genomes and infectious FRNAPH, suggesting recent viral pollution since infectious particles had not been inactivated at sufficient levels in the environment. More generally, this study shows the value of using BMS as an active method for improving knowledge on the behavior of viral contamination in water bodies, the ranking of the contamination sources, and the vulnerability of downstream water bodies.

A Comprehensive Review for the Surveillance of Human Pathogenic Microorganisms in Shellfish.

Bivalve molluscan shellfish have been consumed for centuries. Being filter feeders, they may bioaccumulate some microorganisms present in coastal water, either naturally or through the discharge of human or animal sewage. Despite regulations set up to avoid microbiological contamination in shellfish, human outbreaks still occur. After providing an overview showing their implication in disease, this review aims to highlight the diversity of the bacteria or enteric viruses detected in shellfish species, including emerging pathogens. After a critical discussion of the available methods and their limitations, we address the interest of technological developments using genomics to anticipate the emergence of pathogens. In the coming years, further research needs to be performed and methods need to be developed in order to design the future of surveillance and to help risk assessment studies, with the ultimate objective of protecting consumers and enhancing the microbial safety of bivalve molluscan shellfish as a healthy food.

Trend of Pathogenic Vibrio parahaemolyticus Occurrences in Bivalve Molluscs Harvested in Sardinian Coastal Environments Between 2011 and 2018

The aim of the present study was to evaluate Vibrio parahaemolyticus occurrences in bivalve molluscs harvested from Sardinian coastal environments between 2013 and 2015. The prevalence of pathogenic V. parahaemolyticus isolates is based on the detection of the two major virulence genes thermostable direct hemolysin (tdh) and thermolabile hemolysin (trh) To assess changes between 2011 and 2018 in the prevalence of V. parahaemolyticus in bivalve molluscs, we compared our results with those of previous investigations. In total, 2,933 samples were collected: 1,079 in 2013, 1,288 in 2014, and 566 in 2015. The mean prevalence of V. parahaemolyticus in shellfish was 3.5% in 2013, 1.7% in 2014, and 3.5% in 2015. The highest percentage of positive samples in 2013 and 2014 was observed in clams (3.5% and 2.7%, respectively), whereas in 2015, it was reported in oysters (15.1%). By comparing the sampling period of 2011–2014 with that of 2015–2018, an increase in the prevalence of V. parahaemolyticus was observed in shellfish (p < 0.05). In parallel, 208 potentially enteropathogenic V. parahaemolyticus strains were identified through the years 2011–2018 and, in particular, 10 trh+ and six tdh+ isolates. Our present study provides information regarding trends of V. parahaemolyticus occurrences in bivalve molluscs harvested from Sardinian coastal environments between 2011 and 2018 suggesting that the prevalence varies depending on the sampling period and shellfish species.

SARS-CoV-2 RNA in Wastewater and Bivalve Mollusk Samples of Campania, Southern Italy.

SARS-CoV-2 can be detected in the feces of infected people, consequently in wastewater, and in bivalve mollusks, that are able to accumulate viruses due to their ability to filter large amounts of water. This study aimed to monitor SARS-CoV-2 RNA presence in 168 raw wastewater samples collected from six wastewater treatment plants (WWTPs) and 57 mollusk samples obtained from eight harvesting sites in Campania, Italy. The monitoring period spanned from October 2021 to April 2022, and the results were compared and correlated with the epidemiological situation. In sewage, the ORF1b region of SARS-CoV-2 was detected using RT-qPCR, while in mollusks, three targets-RdRp, ORF1b, and E-were identified via RT-dPCR. Results showed a 92.3% rate of positive wastewater samples with increased genomic copies (g.c.)/(day*inhabitant) in December-January and March-April 2022. In the entire observation period, 54.4% of mollusks tested positive for at least one SARS-CoV-2 target, and the rate of positive samples showed a trend similar to that of the wastewater samples. The lower SARS-CoV-2 positivity rate in bivalve mollusks compared to sewages is a direct consequence of the seawater dilution effect. Our data confirm that both sample types can be used as sentinels to detect SARS-CoV-2 in the environment and suggest their potential use in obtaining complementary information on SARS-CoV-2.

Snapshot of resistome, virulome and mobilome in aquaculture

Aquaculture environments can be hotspots for resistance genes through the surrounding environment. Our objective was to study the resistome, virulome and mobilome of Gram-negative bacteria isolated in seabream and bivalve molluscs, using a WGS approach. Sixty-six Gram-negative strains (Aeromonadaceae, Enterobacteriaceae, Hafniaceae, Morganellaceae, Pseudomonadaceae, Shewanellaceae, Vibrionaceae, and Yersiniaceae families) were selected for genomic characterization. The species and MLST were determined, and antibiotic/disinfectants/heavy metals resistance genes, virulence determinants, MGE, and pathogenicity to humans were investigated. Our study revealed new sequence-types (e.g. Aeromonas spp. ST879, ST880, ST881, ST882, ST883, ST887, ST888; Shewanella spp. ST40, ST57, ST58, ST60, ST61, ST62; Vibrio spp. ST206, ST205). >140 different genes were identified in the resistome of seabream and bivalve molluscs, encompassing genes associated with β-lactams, tetracyclines, aminoglycosides, quinolones, sulfonamides, trimethoprim, phenicols, macrolides and fosfomycin resistance. Disinfectant resistance genes qacE-type, sitABCD-type and formA-type were found. Heavy metals resistance genes mdt, acr and sil stood out as the most frequent. Most resistance genes were associated with antibiotics/disinfectants/heavy metals commonly used in aquaculture settings. We also identified 25 different genes related with increased virulence, namely associated with adherence, colonization, toxins production, red blood cell lysis, iron metabolism, escape from the immune system of the host. Furthermore, 74.2 % of the strains analysed were considered pathogenic to humans. We investigated the genetic environment of several antibiotic resistance genes, including blaTEM-1B, blaFOX-18, aph(3″)-Ib, dfrA-type, aadA1, catA1-type, tet(A)/(E), qnrB19 and sul1/2. Our analysis also focused on identifying MGE in proximity to these genes (e.g. IntI1, plasmids and TnAs), which could potentially facilitate the spread of resistance among bacteria across different environments. This study provides a comprehensive examination of the diversity of resistance genes that can be transferred to both humans and the environment, with the recognition that aquaculture and the broader environment play crucial roles as intermediaries within this complex transmission network.

The impact of climate change and pollution on trematode-bivalve dynamics

Coastal ecosystems and their marine populations are increasingly threatened by global environmental changes. Bivalves have emerged as crucial bioindicators within these ecosystems, offering valuable insights into biodiversity and overall ecosystem health. In particular, bivalves serve as hosts to trematode parasites, making them a focal point of study. Trematodes, with their life cycles intricately linked to external factors, provide excellent indicators of environmental changes and exhibit a unique ability to accumulate pollutants beyond ambient levels. Thus, they act as living sentinels, reflecting the ecological condition of their habitats. This paper presents a comprehensive review of recent research on the use of bivalve species as hosts for trematodes, examining the interactions between these organisms. The study also investigates the combined impact of trematode infections and other pollutants on bivalve molluscs. Trematode infections have multifaceted consequences for bivalve species, influencing various aspects of their physiology and behavior, including population-wide mortality. Furthermore, the coexistence of trematode infections and other sources of pollution compromises host resistance, disrupts parasite transmission, and reduces the abundance of intermediate hosts for complex-living parasites. The accumulation process of these parasites is influenced not only by external factors but also by host physiology. Consequently, the implications of climate change and environmental factors, such as temperature, salinity, and ocean acidification, are critical considerations. In summary, the intricate relationship between bivalves, trematode parasites, and their surrounding environment provides valuable insights into the health and sustainability of coastal ecosystems. A comprehensive understanding of these interactions, along with the influence of climate change and environmental parameters, is essential for effective management and conservation strategies aimed at preserving these delicate ecosystems and the diverse array of species that rely on them.

Factors that facilitate or limit the development of bivalve mollusk aquaculture in BCS, Mexico: The small-scale producers’ perspective

Aquaculture is the activity with the highest economic growth in the fishing sector worldwide. This activity in Baja California Sur (BCS) Mexico is at a key moment due recent upturn in production and the number of operating organizations; regarding bivalve mollusks culture (the livelihood of hundreds of families), but they are unable to stabilize their production. The purpose of this research was to determine the factors that limit/favor the development of the activity, in order to propose strategic actions to improve the situation. For this, through a survey, a political, economic, social and technological, ecological, and legal analysis (PESTEL) were integrated. Among the results stands out that 88% of the companies started activity less than a decade ago, with a higher rate of company creation in the last four years. The producer’s profile shows that they come mainly from fishing and agricultural activities, and two-thirds only have primary or secondary education. As a relevant weakness, only 22% of companies have social security for workers and their families. Environmental conditions, climate, water quality, and high product consumption stand out as favorable aspects. Among the limitations are the shortage of seeds, deficient infrastructure, marketing problems, and lack of financing programs. Within the political factors, producers demand the ordering of the sector. We conclude the need to improve government support programs, seed production, innovation process, productive and commercial articulation, crop diversification, and strengthening of the BCS oyster product network.

Haracteristic of the biology of the European flounder Platichthys flesus (Pleuronectidae) of the lower reaches of the Mezen river according to research data 2010–2016

The biological characteristics of the European flounder of the lower reaches of the Mezen River are described. The maximum age of 18 years was noted, the maximum zoological length and weight: 41,2 cm and 680 g. The size and weight characteristics of individuals for each age are given. The relationship between the length and mass of the river body is described by a power function. Single maturing individuals were caught at the age of 4 years in females and 3 years in males. The bulk of the fish ripens at 4–5 years of age. Food items are marked: amphipods, bivalve mollusks, insect larvae, including brooks, sipunculids, fish objects. The average absolute fecundity of European flounder is 550 thousand eggs.

Five Years Monitoring the Emergence of Unregulated Toxins in Shellfish in France (EMERGTOX 2018-2022).

Shellfish accumulate microalgal toxins, which can make them unsafe for human consumption. In France, in accordance with EU regulations, three groups of marine toxins are currently under official monitoring: lipophilic toxins, saxitoxins, and domoic acid. Other unregulated toxin groups are also present in European shellfish, including emerging lipophilic and hydrophilic marine toxins (e.g., pinnatoxins, brevetoxins) and the neurotoxin β-N-methylamino-L-alanine (BMAA). To acquire data on emerging toxins in France, the monitoring program EMERGTOX was set up along the French coasts in 2018. Three new broad-spectrum LC-MS/MS methods were developed to quantify regulated and unregulated lipophilic and hydrophilic toxins and the BMAA group in shellfish (bivalve mollusks and gastropods). A single-laboratory validation of each of these methods was performed. Additionally, these specific, reliable, and sensitive operating procedures allowed the detection of groups of EU unregulated toxins in shellfish samples from French coasts: spirolides (SPX-13-DesMeC, SPX-DesMeD), pinnatoxins (PnTX-G, PnTX-A), gymnodimines (GYM-A), brevetoxins (BTX-2, BTX-3), microcystins (dmMC-RR, MC-RR), anatoxin, cylindrospermopsin and BMAA/DAB. Here, we present essentially the results of the unregulated toxins obtained from the French EMERGTOX monitoring plan during the past five years (2018-2022). Based on our findings, we outline future needs for monitoring to protect consumers from emerging unregulated toxins.