Mussel Mytilus Edulis Research Articles

Blue mussel (Mytilus edulis) hydrolysates attenuate oxidized-low density lipoproteins (ox-LDL)-induced foam cell formation, inflammation, and oxidative stress in RAW264.7 macrophages

Seafood consumption has a great demand in the world due to its array of health benefits. Marine-derived bioactive peptides and hydrolysates have been found to have multifunctional health benefits. In this study, inhibitory effects of blue mussel hydrolysates, including blue mussel Alcalase® hydrolysate (BMAH) and blue mussel-pepsin hydrolysate (BMPH), on foam cell formation in ox-LDL-induced RAW264.7 macrophages were investigated. BMAH inhibited lipid accumulation evidenced by Oil Red O staining. Its inhibitory effect was higher than that of BMPH. BMAH positively modulated levels of total cholesterol, free cholesterol, and cholesterol ester in model cells. It suppressed cholesterol influx by downregulating SR-A1 and CD36 expression, but increased cholesterol efflux by upregulating ABCA-1 and ABCG-1 expression. In addition, ox-LDL treated RAW264.7 macrophages produced inflammatory responses and oxidative stress during foam cell formation. However, BMAH treatment significantly ameliorated proinflammatory cytokines production (TNF-α, IL-6, and IL-1β) by inhibiting NF-κB nuclear translocation. Moreover, BMAH inhibited intracellular reactive oxygen species (ROS) generation by activating HO-1/Nrf2 signaling pathway in ox-LDL-treated RAW264.7 macrophages. Taken together, these results suggest that BMAH might be useful as an ingredient of functional foods to ameliorate the development of atherosclerosis.

Size and site specific transcriptomic responses of blue mussel (Mytilus edulis) to acute hypoxia.

The Prince Edward Island (PEI) mussel aquaculture industry is being challenged by climate change induced environmental stressors including hypoxic/anoxic episodes, that can impact mussel health and survival. Physiological responses of mussels to hypoxia/anoxia have been studied; however, less is known about how transcriptomic response leads to physiology. The present study examined the transcriptomic response of acute (4h) hypoxia in blue mussels (Mytilus edulis) from two sites and size classes in PEI, Canada. Overall, major changes in whole-mussel transcriptomics associated with metabolism, cellular organelles/processes and environmental sensing were observed in the first hours of hypoxia exposure. Differences in differentially expressed transcripts were observed between each site and size, indicating that responses to acute hypoxia exposure are highly complex. A size related pattern was observed, with seed size mussels having differential expression of transcripts associated with development, muscle function, and byssal attachment compared to the adults. Adult mussels had higher HSP 90 expression, while HSPs were predominately under-expressed in seed mussels. Seed mussels had significant under-expression of several classes of byssal thread attachment transcripts, indicating a decline in the production of byssal thread or detachment, both which have negative consequences for mussel aquaculture.

The effect of surface orientation on early successional fouling communities in the southern gulf of Maine

Artificial environments have hard surfaces positioned at different orientations that attract a wide diversity of sessile invertebrate species, forming fouling communities. Fouling communities play a large role in the spread of a species introduction, as organisms gain purchase in artificial environments and use them as a stepping-stone into neighboring natural systems. These man-made systems harbor a large diversity of species, and there are often vastly different communities present on both vertical and horizontal surfaces. We used a species abundance dataset at three time periods spanning 30 years, collected from fouling panels in a high tidal flow estuary at the mouth of the Piscataqua River (New Castle, New Hampshire) in the southern Gulf of Maine to measure differences in community composition between horizontal and vertical panels. Early successional communities on settlement panels were photographed one year after installment in late summer to capture the highest diversity seasons. Organisms were then identified to the lowest taxonomic level, and communities on the underside of horizontal and vertical panels were compared. Vertical and horizontal communities from 1980 and 2004 were similar, while those from 2009 statistically differed from one another. Vertical and horizontal surfaces in the 1980s were dominated by the blue mussel Mytilus edulis, which declined in later years, and was replaced by invasive ascidians. Species diversity increased between the 1980 and 2004 sampling, but declined by the 2009 sampling. This study captures changes of species composition in early successional communities on vertical and horizontal surfaces at a single locale from three time periods spanning over 30 years.

Gaping behaviour of Blue mussels (Mytilus edulis) in relation to freshwater runoff risks

Shellfish grown for food are vulnerable to environmental contamination, potentially rendering them unsafe for human consumption. Non-invasive gape (valve openness) sensing allows in-situ monitoring of bivalve shellfish behaviours, such as feeding, that can result in exposure to contaminated waters. Sensors were attached to Blue mussels and deployed for 10 days on natural mussel beds in Dundrum Bay, Northern Ireland. Data showed a tidally synchronous behaviour pattern of high openness at high water and vice versa. It is likely that this is, at least in part, due to extreme salinity variation (1.8–33.6) resulting from near total water exchange with each tide in the bay. This behaviour is likely to infer a degree of protection from contaminants during periods of low water, a time at which runoff-derived pollutants are most concentrated.

Mineral-free biomaterials from mussel (Mytilus edulis L.) shells: Their isolation and physicochemical properties

One of the modern directions of mussel shells utilisation is associated with the production of mineral-free biomaterials that can be successfully used in food production, feed additives production, in biotechnologies, as well as in biomedicine. The objectives of this study are to obtain an organic matrix (conchix) from mussel (Mytilus edulis L.) shells by demineralisation using two decalcifying agents—a solution of hydrochloric acid (HCl) and a solution of disodium salt of ethylenediaminetetraacetic acid (Na2-EDTA), as well as the influence of the decalcifying agent nature on the organic matrix structure. The degree of demineralisation of the obtained conchixes when using HCl reaches 100%. It has been shown that the native structure of the organic matrix proteins is partially destroyed during the demineralisation of the shells in the HCl solution; analysis of IR spectra indicates a 1.5-fold decrease in the number of α-helices compared to the organic matrix obtained by gentle Na2-EDTA-based demineralisation. SEM and TEM studies indicate the destruction of the biopolymer structure of the outer (periostracum) and inner (prismatic and nacreous) layers of the organic matrix obtained using HCl, while this structure is completely preserved when using Na2-EDTA. The results obtained indicate the preference of using Na2-EDTA for the production of biomaterials with potential use in food technology and biomedicine.

Using a biodegradable substrate to increase transplantation success: Effect of density and sediment on aggregation behavior of mussels

Habitat restoration through transplantation of ecosystem engineering species has become an increasingly popular conservation strategy. However, the success of these restoration efforts depends largely on the ability of transplanted organisms to establish and persist in their new environment. Ecosystem engineers typically occur in large numbers and rely on self-facilitating feedback mechanisms to overcome physical and/or biological stressors for successful establishment. These feedback mechanisms can only arise when a certain density or size threshold is reached and are driven by the interplay of facilitation and competition. To initiate the establishment of self-facilitating feedback mechanism, we used biodegradable structures known as “BioShell-SMCs”. These structures are an innovation of the nylon seed mussel collectors (SMCs) commonly used in mussel cultivation. They consist of a biodegradable net based on a compound of aliphatic polyesters, filled with empty cockle shells around a coconut fiber rope. In a mesocosm experiment, we investigated competition and facilitation processes by comparing aggregation and performance between loose seeded blue mussels (Mytilus edulis) and mussels already attached to the BioShell-SMC at two different densities (high vs. low) and two sediment compositions (mud vs shell). Our results revealed that mussels attached to the BioShell-SMC showed more pronounced clustering compared to loose mussels, particularly in low density. Mussels in high density attached to the BioShell-SMC dispersed from the SMC on both sediment compositions. Furthermore, transplanted mussels attached to the BioShell-SMC showed higher survival rates and had a better condition than loose mussels. Overall, our study emphasizes the importance of considering ecological processes such as competition and facilitation when designing and implementing restoration projects. It provides a case for optimizing transplantation success of ecosystem engineers by including temporary substrate that provide positive feedback mechanisms at establishment, effectively creating a window of opportunity.

Flexibility and Function of Distal Substrate-Binding Tryptophans in the Blue Mussel β-Mannanase MeMan5A and Their Role in Hydrolysis and Transglycosylation

β-Mannanases hydrolyze β-mannans, important components of plant and microalgae cell walls. Retaining β-mannanases can also catalyze transglycosylation, forming new β-mannosidic bonds that are applicable for synthesis. This study focused on the blue mussel (Mytilus edulis) GH5_10 β-mannanase MeMan5A, which contains two semi-conserved tryptophans (W240 and W281) in the distal subsite +2 of its active site cleft. Variants of MeMan5A were generated by replacing one or both tryptophans with alanines. The substitutions reduced the enzyme’s catalytic efficiency (kcat/Km using galactomannan) by three-fold (W281A), five-fold (W240A), or 20-fold (W240A/W281A). Productive binding modes were analyzed by 18O labeling of hydrolysis products and mass spectrometry. Results show that the substitution of both tryptophans was required to shift away from the dominant binding mode of mannopentaose (spanning subsites −3 to +2), suggesting that both tryptophans contribute to glycan binding. NMR spectroscopy and molecular dynamics simulations were conducted to analyze protein flexibility and glycan binding. We suggest that W240 is rigid and contributes to +2 subsite mannosyl specificity, while W281 is flexible, which enables stacking interactions in the +2 subsite by loop movement to facilitate binding. The substitutions significantly reduced or eliminated transglycosylation with saccharides as glycosyl acceptors but had no significant effect on reactions with alcohols.

Molecular confirmation of pearl formation in arctic mussels (Mytilus edulis) caused by Gymnophallus bursicola (Odhner 1900) metacercariae.

In recent field studies, suspected gymnophallid metacercariae were histologically located in the mantle of mussels from the Norwegian Sea. Mussels from the sites in which that infection was detected also presented abnormally high pearl numbers. It has been previously described that gymnophallid metacercariae could cause pearl formation processes in mussels, as a host reaction to encapsulate these metacercariae. Given the pathological host reaction these parasites elicit, a study was performed to identify gymnophallid metacercariae found in mussels collected from Tromsø at morphological and molecular level and to assess, by the use of molecular tools, the relationship between the parasite and the biological material inside the pearls. As a result, Gymnophallus bursicola metacercariae infecting Norwegian Mytilus edulis were identified according to morphological characters, along with the first 18S rDNA and COI sequences for this trematode species. In addition, parasite DNA from the core of the pearls was extracted and amplified for the first time, confirming the parasitological origin of these pearls. This procedure could allow identifying different parasitic organisms responsible for the generation of pearls in bivalves.

Seasonal fluctuations of hemolymph microbiota and immune parameters in Mytilus galloprovincialis farmed at La Spezia, Italy

Marine bivalves include economically highly important aquacultured species worldwide (oysters, mussels, clams, scallops). Although one third of production in Europe is represented by mussels (Mytilus edulis, M. galloprovincialis) a significant decline has been observed in the last two decades, whose causes are likely to be multifactorial, from the presence of pathogens to climate change, often exacerbated by local conditions, leading to mortality outbreaks.Knowledge of the composition of the microbial communities, together with their relationship with the host, represents a primary target for understanding bivalve health in different environmental conditions. The microbiome is strongly influenced by both local environmental factors and endogenous factors, such as the host immune status. However, information on the seasonal fluctuations of microbial communities in mussels, together with immune parameters, is still lacking.In the present work, M. galloprovincialis cultivated in north-western Italy (La Spezia) were sampled from February to November 2020 and hemolymph microbiome was evaluated using 16S rRNA gene, together with a set of immune biomarkers in hemocytes (lysosomal membrane stability-LMS, phagocytic activity, ROS production) and soluble lysozyme activity, and parameters of general health conditions (gametogenesis, survival in air).The results show that M. galloprovincialis hemolymph microbiota was characterized by the constant presence of 8 bacterial genera (Vibrio, Pseudoalteromonas, Tenacibaculum, Colwellia, Shewanella, Amphritea, and 2 from the Arcobacteracea family, Halarcobacter and Arcobacter-like). Seasonal changes in their relative abundance were observed, showing a distinct pattern in winter (February–November) and summer (July, September). Water temperature contributed to shaping the microbiota composition, in particular with regards to the abundance of Vibrios, Psychrilobacter and Photobacterium, Halarcobacter and Arcobacter-like, that was favored by higher temperatures. Seasonal variations of LMS and phagocytosis were also observed, indicating a reduced immunocompetence in winter, concomitant with general stressful conditions associated with spawning. In contrast, the main fluctuations in extracellular immune defences (ROS and lysozyme) were apparently independent of temperature or gametogenic stage. Overall, the results confirm the robustness of mussel immune system, at the same time underlying the potential susceptibility to disease at certain times of the year to additional stressful conditions (i.e. pathogen challenge, pollutant exposure, or further changes in water chemico-physical parameters). These data provide background information useful for monitoring local mussel farming and predicting potential impacts of changing environmental conditions.

Integrated assessment of biological responses to pollution in wild mussels (Mytilus edulis) from subarctic and arctic areas in the Norwegian sea

North Atlantic and Arctic Oceans contain large amount of undiscovered oil and gas reserves. Therefore threat of oil spills and its hazardous ecological consequences are of great importance to the marine environment. Although mussels (Mytilus sp.) respond clearly to contaminants, biomarkers have shown variability linked to biological and environmental changes. In order to help avoiding misinterpretation of biological responses the aim of this study was to reveal the effect of natural variability in the responsiveness to pollution of a battery of cell and tissue-level biomarkers in mussels. Mussels were collected in relatively non-impacted and potentially impacted sites at ports and the vicinity of a waste water treatment plant in Trondheim and Tromsø in autumn of 2016. Although the battery of biomarkers used herein proved to be useful to discriminate impacted and non-impacted mussel populations, some confounding factors altering the biological responses were identified. Geographical/latitudinal factors seemed to be critical regarding the reproductive cycle, reserve material storage and the prevalence of parasites such as Gymnophallus cf. Bursicola trematodes. Mussels from the reference site in Tromsø displayed general stress responses at different levels, which could be influenced by the pathogenic effect of the Gymnophallus cf. Bursicola trematode and by a more advanced gametogenic developmental stage compared to the mussels from Trondheim, which could lead to misinterpretation of the reasons behind the measured stress levels in those mussels. Despite these confounding effects, the use of integrative tools such as IBR index helped to discriminate mussel populations from chemically impacted and non-impacted sites. Overall, this work serves as an anchor point both as a reference of the baseline level values of the analyzed endpoints in the studied geographical area and time of the year, and as an indication of the potential extent of the environmental confounding factors in monitoring programs causing stress on the analyzed mussel populations.

Study of the ageing and the sorption of polyaromatic hydrocarbons as influencing factors on the effects of microplastics on blue mussel

The mussels are species with high socio-economic weights and are often used as bioindicators of biological and chemical contamination. In the field and aquaculture, they can intake microplastics during filter-feeding, and the microplastics can have a negative impact on their health, even at low concentrations. The effects of microplastics have yet to be fully examined on the blue mussel (Mytilus edulis), considering the factors of ageing and sorption of some polyaromatic hydrocarbons (PAHs), ubiquitous environmental contaminants. In this work, 5 different exposure conditions were studied: pristine microplastics, microplastics aged for 1000 days under UV radiation, microplastics sorbing PAHs, as well as microplastics both aged and sorbing PAHs, in parallel to controls. The microplastic changes after ageing were studied with spectroscopic and chromatographic methods. Then, 8-day laboratory exposures of mussels at 10 µg/L of microplastics were performed. The oxidative stress, as well as neurotoxic and immunological responses of M. edulis, were measured using a battery of biomarkers (catalase/CAT, superoxide dismutase/SOD, glutathione S-transferases/GST, acetylcholinesterase/AChE) in 3 different organs (digestive gland, gills and mantle), and acid phosphatase in hemolymph. Then, a study of lipid impairments on the digestive gland was performed through the use of lipidomic tools. No significant difference of oxidative stress activity was observed for all the tissues of mussels exposed to pristine microplastics at 10 µg/L, compared to controls. The ageing and the PAH soption onto microplastics were influencing factors of the oxydative stress in mussels with increased CAT activities in the digestive glands and decreased SOD activities in the mantles. The neurotoxicity was highlighted by higher AChE activities measured in the mantle of mussels exposed to all the microplastic treatments, compared to controls. Concerning lipidomics, no compound was determined as a biomarker of microplastic exposure. The study demonstrated a low toxicity of microplastics at environmental relevant concentration with a 8-day exposure and using the chosen biomarkers. However, some microplastic changes seemed to lead to specific effects on mussels.

Temporal and small-scale spatial variation in spatfall of the mussel Mytilus edulis platensis: Basis for culture management at San Jorge Gulf, Patagonia Argentina

Despite the commercial potential of mussel populations along the Patagonian coast of Argentina, studies on mussel farming and fisheries to the south of parallel 42° S are clearly insufficient thus far. In this study, variations in mussel settlement (between sites and across depths) were monitored for 12 months at two contrasting sites in San Jorge Gulf, Argentina. The effect of depth on spat density was evaluated through monthly samples taken from artificial collectors at three depths (3, 7 and 11 m). The temporal settlement pattern was consistent at both sites, with the maximum spatfall recorded in early March (late summer), coinciding with the peak of sea water temperature. Settlement also correlated with Chl a and particulate organic carbon peak values, typically manifesting 2–3 months later and followed the initial decline in mussel condition during late spring and early summer. Significant differences between localities were detected in settlement abundance. The optimal temporal gap for mussel settlement was observed in mid / late summer, suggesting that this is the optimal time to deploy spat collectors in the field. Settlement was uniform between depths, thereby implying that the specific depth of collector placement did not appear to emerge as a key factor of settlement success.

Increasing mussel transplantation success by initiating self-facilitating feedback mechanisms

Transplantation success of ecosystem-engineering species can be low in dynamic environments, as such ecosystem-engineers often require density-dependent positive feedback mechanisms to overcome environmental stressors. These self-facilitating feedback mechanisms play an important role in self-organization, whereby complex systems tend to organize and create patterns in order to ameliorating physical and/or biological stressors. In this study we used biodegradable structures to ameliorate self-facilitating feedback mechanisms to overcome environmental stressors in the initial post-transplantation phase. The biodegradable structures tested are an innovation of the traditional Seed Mussel Collectors (SMCs) used in mussel cultivation. The so-called “BioShell-SMC” does not contain any plastic, but is made up of a coconut fiber rope surrounded by empty cockle shells and held together by a biodegradable net based on a compound of aliphatic polyesters. We tested if the survival of two size classes of blue mussel (Mytilus edulis) transplants, on a tidal flat in the Oosterschelde estuary in the Netherlands, increased when mussel seed was transplanted attached to the BioShell-SMCs instead of single mussels in combination with empty cockle shells. The results of this study revealed that the survival of larger mussel seed significantly improved when attached to the BioShell-SMC compared to those transplanted loosely. Factors contributing to the difference in mussel loss between BioShell-SMC mussels and loosely transplanted mussels include predation, competition and dislodgement due to hydrodynamic forces. For small mussel seed, mussel biomass decreased strongly in the first three days of the experiment, irrespective of transplantation method. This is due the small size of the mussels in combination with low mussel densities. Overall, this study highlights the potential of using biodegradable structures to initiate self-facilitating feedback mechanisms in establishment of ecosystem engineers in dynamic environments.

Home sweet home: Comparison of epibiont assemblages associated with cultivated and wild sugar kelp (Saccharina latissima), co-cultivated blue mussels (Mytilus edulis) and farm infrastructure

Seaweed farming is expanding in Europe and may provide environmental benefits similar to those from natural kelp forests and shellfish farms, including habitat provisioning. Few studies have substantiated these claims however, and it remains uncertain whether seaweed farms will support similar biodiversity to kelp forests or provide valuable long-term habitat beyond the harvest season. We repeatedly surveyed an integrated sugar kelp (Saccharina latissima) and blue mussel (Mytilus edulis) farm in southwest UK to compare epibiont assemblages between cultivated kelps, to those from three nearby wild kelp populations, and to epibionts on farmed mussel lines and unseeded ‘bare’ lines. We found farmed kelps supported over 217 times the abundance of epibionts living on wild kelps at harvest time, however, taxonomic diversity per kelp was lower at the farm. Farmed kelp assemblages were dominated by amphipods, which were present on the wild kelps but in much lower numbers. Farmed kelp also supported distinct assemblages to cultivated mussels, which were similarly dominated by amphipods, but hosted higher relative abundances of crabs, echinoderms, worms and red algal biomass. The bare lines were heavily colonised by another pseudo-kelp, Saccorhiza polyschides, which supported similar epibiont assemblages to the seeded S. latissima lines. Our findings indicate that cultivating bivalves alongside seaweed can increase habitat provisioning at a seaweed farm and extend its permanence beyond typical seaweed cultivation periods as bivalves have longer, continuous farming periods. However, the presence of mussels will likely influence the epibiont assemblages on the farmed kelp, which are distinct from wild kelp populations.

Filtration and respiration responses of mussels (Mytilus edulis) to trematode parasite infections (Renicola roscovita) and transient heat exposure.

The mussel Mytilus edulis, a host to various trematode species, experiences performance decrements due to these infections. Yet, the impact magnitude and potential interactions with environmental stressors remain largely unexplored. This study scrutinizes the effect of Renicola roscovita infections on mussel filtration and respiration. We first assessed performance in both uninfected and lab-infected mussels at a mild temperature (16°C), following an acute heat ramp to 30.5°C and subsequent cooling. The experiment revealed neither a significant direct impact of the infection on the mussels' performance, nor any significant interplay between the infection and temperature variations. To account for possible infection effects obscured by low sample sizes or mussel size disparities, we conducted a reassessment at 16°C using both small and large mussels. Infection notably hampered filtration in large mussels, with a marginal impact on smaller ones. A positive correlation was found between infection intensity and mussel filtration capacity, though the infection had no discernible impact on respiration. Our consistent finding of an 11-12 % infection effect size across all experiments indicates a slight reduction in mussel filtration due to trematode infections. While the exacerbating effect of transient heat stress on the infection's impact on filtration was not statistically significant, future investigations should explore potential interactions with prolonged heat stress. Our findings underscore the nuanced ways in which parasitic infections can influence marine bivalve physiology, emphasizing the need for more comprehensive studies that incorporate environmental stressors, such as heat stress, to fully elucidate the impact of parasitism on marine ecosystem health and resilience.

Drying and Rehydration Characteristics of Microwave Dried Mytilus edulis

Rehydration is a critical factor in the processing and consumption of dried food products. This study investigated the kinetics of microwave drying and rehydration of blue mussels (Mytilus edulis) in the range of 140 - 350 W power levels and 20 - 40°C temperatures, respectively. The drying data were utilized to calculate effective diffusivity coefficients (Deff) and activation energy (EA), while rehydration rates and time were also determined. Mathematical modeling was employed to describe the drying and rehydration processes, and the performance of different models was evaluated. The drying process took between 13 - 4.5 minutes, while rehydration was concluded within 360 - 480 minutes. The Deff values ranged from 1.22 - 3.91×10-7 m2/s, and the EA was calculated as 11.417 kW/kg. Rehydration rates resulted in 0.000061 - 0.000126 g/g×min at the highest 40°C and 0.000018 - 0.000032 g/g×min at the lowest 20°C. The drying and rehydration processes were best described by the Alibas model among 11 models and the Two-Term Exponential model among 2 models, respectively. Overall, this study aims to provide valuable insights into the kinetics of microwave drying and rehydration of blue mussels, which can help optimize the processing and preservation of dried food products before consumption.

Arsenic speciation in low-trophic marine food chain – An arsenic exposure study on microalgae (Diacronema lutheri) and blue mussels (Mytilus edulis L.)

Microalgae and blue mussels are known to accumulate undesirable substances from the environment, including arsenic (As). Microalgae can biotransform inorganic As (iAs) to organoarsenic species, which can be transferred to blue mussels. Knowledge on As uptake, biotransformation, and trophic transfer is important with regards to feed and food safety since As species have varying toxicities. In the current work, experiments were conducted in two parts: (1) exposure of the microalgae Diacronema lutheri to 5 and 10 μg/L As(V) in seawater for 4 days, and (2) dietary As exposure where blue mussels (Mytilus edulis L.) were fed with D. lutheri exposed to 5 and 10 μg/L As(V), or by aquatic exposure to 5 μg/L As(V) in seawater, for a total of 25 days. The results showed that D. lutheri can take up As from seawater and transform it to methylated As species and arsenosugars (AsSug). However, exposure to 10 μg/L As(V) resulted in accumulation of iAs in D. lutheri and lower production of methylated As species, which may suggest that detoxification mechanisms were overwhelmed. Blue mussels exposed to As via the diet and seawater showed no accumulation of As. Use of linear mixed models revealed that the blue mussels were gradually losing As instead, which may be due to As concentration differences in the mussels’ natural environment and the experimental setup. Both D. lutheri and blue mussels contained notable proportions of simple methylated As species and AsSug. Arsenobetaine (AB) was not detected in D. lutheri but present in minor fraction in mussels. The findings suggest that low-trophic marine organisms mainly contain methylated As species and AsSug. The use of low-trophic marine organisms as feed ingredients requires further studies since AsSug are regarded as potentially toxic, which may introduce new risks to feed and food safety.

An explainable machine learning for geographical origin traceability of mussels Mytilus edulis based on stable isotope ratio and compositions of C, N, O and H

Geographical traceability of marine bivalves has been explored continually, however the traceability results have not been recognized owing to the absence of a reasonable explanation for a certain model prediction. To address this problem, we employed an explainable machine learning to identify the origin of mussels based on stable isotope ratio and compositions of carbon (C), nitrogen (N), oxygen (O), and hydrogen (H). Our findings proved that the Extreme gradient boosting (XGBoost) model may be the best model based upon its high accuracy (93.75 %), precision (93.75 %), recall (94.51 %), F1 score (93.72 %) and AUC (0.990). The feature impact for model out of XGBoost was interpreted by SHapley Additive exPlanations (SHAP) on global and local perspective. This study demonstrated the potential of explainable machine learning to elucidate the complex relationships between desirable geographical information of mussels and the selected features.

Aliens eating aliens: an introduced amphipod as a potential prey of an invasive rocky shore crab in laboratory experiments

Behavioural interactions between introduced predators and introduced prey are still largely underestimated. The present work takes advantage of the co-occurrence of two introduced species, the Asian shore crab Hemigrapsus sanguineus and the amphipod Ptilohyale littoralis, respectively first recorded on rocky shores along the French coast of the eastern English Channel in 2005 and 2016. In this context, the predation by male and female H. sanguineus on P. littoralis was examined under controlled laboratory conditions, by presenting either juveniles of the blue mussel Mytilus edulis or adult P. littoralis to H. sanguineus. We subsequently assessed the potential prey preference of the Asian shore crab for P. littoralis and M. edulis by presenting the two prey items simultaneously in the same proportion. In the absence of choice, male H. sanguineus preyed significantly more on M. edulis than P. littoralis. In contrast, females preyed significantly less on M. edulis than P. littoralis; however, male and female H. sanguineus consumed similar numbers of P. littoralis. When choice was possible between P. littoralis and M. edulis, the crab did not exhibit preference strictosensu for any type of prey. These results suggest that the Asian shore crab cannot be considered as a naive predator when confronted to a newly introduced prey. Our results also suggest that the amphipod P. littoralis did not exhibit any effective antipredator response towards the crab. These observations nevertheless warrant further work on the effects of abiotic factors (e.g. temperature) as well as other biotic interactions (e.g. presence of other prey or predators for H. sanguineus) may have on the observed prey-predator interactions between H. sanguineus and M. edulis and P. littoralis.

Validation of the male-specific ORF of the paternally-transmitted mtDNA in Mytilus edulis as a protein-coding gene

There appears to be an additional set of sex-specific mtDNA-encoded proteins in bivalve species with doubly uniparental mitochondrial inheritance that may be involved in the transmission of the female and male mitogenomes. In the marine mussel Mytilus edulis, the translation of the female-specific open reading frame (F-ORF) was demonstrated but the translation of the male-specific ORF (M-ORF) remains to be shown. Here we validate the male-specific ORF of the paternal mitogenome in M. edulis as a protein-coding gene. The M-ORF protein was detected only in male gonads and localized in sperm mitochondria and acrosome, suggesting that it is involved in a key sperm function in Mytilus edulis.