Unraveling the interplay between environmental microplastics and salinity stress on Mytilus galloprovincialis larval development: A holistic exploration

The rise of plastic production has triggered a surge in plastic waste, overwhelming marine ecosystems with microplastics. The effects of climate change, notably changing salinity, have shaped the dynamics of coastal lagoons. Thus, understanding the combined impact of these phenomena on marine organisms becomes increasingly crucial. To address these knowledge gaps, we investigated for the first time the interactive effects of environmental microplastics (EMPs) and increased salinity on the early development of Mytilus galloprovincialis larvae. Morphological assessments using the larval embryotoxicity test revealed larval anomalies and developmental arrests induced by EMPs and increased salinity. Transcriptomic analyses targeting 12 genes involved in oxidative stress, apoptosis, DNA repair, shell formation, and stress proteins were conducted on D-larvae uncovered the potential effects of EMPs on shell biomineralization, highlighting the role of Histidine Rich Glycoproteine (HRG) and tubulin as crucial adaptive mechanisms in Mytilus sp. in response to environmental shifts. Furthermore, we explored oxidative stress and neurotoxicity using biochemical assays. Our findings revealed a potential interaction between EMPs and increased salinity, impacting multiple physiological processes in mussel larvae. Our data contribute to understanding the cumulative effects of emerging anthropogenic pollutants and environmental stressors, emphasizing the need for a holistic approach to assessing their impact on marine ecosystems.

Evaluation of the health of Mediterranean mussels (Mytilus galloprovincialis Lamarck, 1819) distributed in the Çanakkale strait, Turkey

The observation of mortality in Mediterranean mussels (Mytilus galloprovincialis) distributed in the Çanakkale Strait in recent years was influential in developing the research question for this study. In this study, the presence of bacteria (Vibrio spp.) and parasites (Marteilia spp. and Haplosporidium spp.) in mussels collected from Kumkale, Kepez, and Umurbey stations in the Çanakkale Strait was investigated seasonally. Microbiological findings, histopathology, oxidative stress enzymes and their gene expressions, lipid peroxidation, lysosomal membrane stability, and changes in haemolymph were examined. In summer samples, both the defence system and the extent of damage were higher in gill tissue. In winter samples, enzyme activities and lipid peroxidation were found to be predominantly higher in digestive gland tissues. Histological examinations and Hemacolor staining revealed the presence of protozoan cysts, and for bacterial examination, molecular analysis performed after culturing revealed the presence of 7 Vibrio species. While the total numbers of heterotrophic bacteria detected in all samples were at acceptable levels, the predominance of Vibrio spp. numbers among the total heterotrophic bacteria detected in almost all samples were noteworthy. The total hemocyte count was calculated as 5.810(4)±0.58 (cells/mm3) in winter and 7.210(4)±1.03 (cells/mm3) in summer. These factors are considered to be possible causes of mussel mortality.

Evaluation of biotoxins and toxic metal risks in mussels from the Sea of Marmara following marine mucilage

The mucilage phenomenon observed in the Sea of Marmara in 2021, has raised public concern about seafood safety. Mediterranean mussels serve as a vehicle in food chain, enabling the transfer of pollutants. Farmed and wild mussels were collected from 4 different stations throughout the fishing season. Biotoxins causing amnesic, paralytic, or diarrhetic shellfish poisonings (ASP, PSP, or DSP) were examined during monthly samplings. Potential health risks posed by cadmium, lead and arsenic were assessed. Health risks were evaluated considering 150 g/week mussel consumption, accounting for the different age groups of consumers (50, 60, 70 kg). Estimated Weekly Intake calculations of metals were determined to be lower than Provisional Tolerable Weekly Intake at all age groups throughout the sampling period in all stations. Target Hazard QuotientCd of mussels captured from Istanbul Strait was always determined <1, while it was equal to 1 for 50 kg individuals in Gelibolu samples. All THQAs were >1. Target carcinogenic Risk was evaluated for Pb and iAs, which were found to be negligible and acceptable, respectively. No biotoxins responsible for ASP, PSP, or DSP were detected. Hg levels were under detectable limits. Excluding Cd, the results did not reveal any risks associated with mussel consumption during mucilage.

Seasonal dynamics of the microbiome-host response to pharmaceuticals and pesticides in Mytilus galloprovincialis farmed in the Northwestern Adriatic Sea

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.

CO2 budget of cultured mussels metabolism in the highly productive Northwest Iberian upwelling system

Assessing the carbon footprint of marine bivalve aquaculture demands an accurate estimation of the CO₂ release associated to capital goods and aquaculture operations but also to the metabolic CO₂ budget of the cultured species. Nowadays, there are discrepancies on the processes to include in that budget, how to estimate them, and which scale should be applied, from individual to ecosystem. Site-specific environmental conditions and culture methods also affect significantly the estimates. Here, we have gathered environmental, biochemical and metabolic data from published scientific articles, reports and existing databases to present the metabolic CO₂ budget for mussel aquaculture in the coastal inlets of the Northwest Iberian upwelling. We analyse the contribution of mussel flesh and shell production jointly and separately. At the individual scale, the shell CO₂ budget is estimated from CO₂ removal by shell matrix protein synthesis and CO₂ release during calcification and respiration to support shell maintenance. Organic carbon in mussel flesh and CO₂ released by respiration to support flesh maintenance contribute to the flesh CO₂ budget. Only calcification and respiration processes are considered when estimating the metabolic carbon footprint of individual mussels because organic carbon in mussel flesh and shell returns to the atmosphere as CO₂ in a relatively short period. While the metabolic carbon footprint associated to mussel shell remains constant at 365 kg CO₂ per ton of shell, it varies from 92 to 578 kg CO₂ per ton of mussel flesh. This large variability depends on mussel seeding time and harvesting size, due to the differential seasonal growth patterns of flesh and shell. Inclusion of the CO₂ potentially immobilised in mussel faeces buried in the sediments would lead to a reduction of the metabolic carbon footprint estimates by up to 6 % compared with the individual estimates.

(Mediterranean Mussels) from Izmir Bay (Turkey)

In this study, cellular biomarkers and heavy metal concentration in the Mytilus galloprovincialis L. (Mediterranean mussels) collected from eight sites of Izmir Bay (Turkey) were determined to reveal water pollution for the first time in these stations. Results show that heavy metals (As, Cu, Hg, Zn, Cd, Sn, Pb) have been specified in mussels' tissues collected from all stations. According to GST, SOD, CAT activities, and TBARS contents, mussels in the outer bay have exposed more oxidative stress than the ones in the inner bay. Digestive gland tissues of them were showed more inhibition at AChE levels than gills. Also, abnormal nucleus rates and micronucleus frequencies (MN) were found to be higher in the inner bay than in the outer bay. This study showed that heavy metal pollution in different levels is an environmental issue on the Izmir Bay. Especially the coastal regions of the bay have been extremely affected by anthropogenic effects due to growing population.

Assessing the effects of the cytostatic drug 5-Fluorouracil alone and in a mixture of emerging contaminants on the mussel Mytilus galloprovincialis

The assessment of contaminants of emerging concern, alone and in mixtures, and their effects on marine biota requires attention. 5-Fluorouracil is a cytostatic category 3 anti-cancer medication (IARC) that is used to treat a variety of cancers, including colon, pancreatic, and breast cancer. In the presence of other pollutants, this pharmaceutical can interact and form mixtures of contaminants, such as adhering to plastics and interaction with metal nanoparticles. This study aimed to comprehend the effects of 5-Fluorouracil (5FU; 10 ng/L) and a mixture of emerging contaminants (Mix): silver nanoparticles (nAg; 20 nm; 10 μg/L), polystyrene nanoparticles (nPS; 50 nm; 10 μg/L) and 5FU (10 ng/L), in an in vivo (21 days) exposure of the mussel Mytilus galloprovincialis. A multibiomarker approach namely genotoxicity, the antioxidant defence system (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), glutathione - S - transferases (GST) activities), and oxidative damage (LPO) was used to assess the effects in gills and digestive gland of mussels. Both treatments cause genotoxicity in mussel's haemolymph, and antagonism between contaminants was observed in the Mix. Genotoxicity observed confirms 5FU's mode of action (MoA) by DNA damage. The antioxidant defence system of mussels exposed to 5FU kicked in and counter balanced ROS generated during the exposure, though the same was not seen in Mix-exposed mussels. Mussels were able to withstand the effects of the single compound but not the effects of the Mix. For oxidative stress and damage, the interactions of the components of the mixture have a synergistic effect.

Impact of Nickel Oxide Nanoparticles (NiO) on Oxidative Stress Biomarkers and Hemocyte Counts of Mytilus galloprovincialis

In this study, the toxic effects of nickel oxide nanoparticles (NiO-NPs) on the model organism Mediterranean mussel (Mytilus galloprovincialis) gill, digestive gland, and hemolymph tissues for 96 h were investigated. Lipid peroxidation (MDA) determination was performed to reveal the oxidative stress generation potential of nanoparticles, and superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase (GST) enzyme levels were measured to determine antioxidant responses. Lysosomal membrane stability and total hemocyte counts were performed to determine cytotoxic effects. All parameters were altered in different concentrations of NiO-NPs (2, 20, and 200 mg L^-1). The SOD levels increased depending on the concentration (p < 0.05), and the increases in CAT, GPx, and GST levels were lower at 20 mg L^-1 concentration (p < 0.05). There was a slight difference between the exposure and the control groups in terms of GR enzyme. The MDA level increased in parallel with the concentration (p < 0.05), the stability of the cell membrane (p < 0.05), and the number of hemocyte cells decreased as a result of exposure (p < 0.05). The results emphasize that NiO-NPs may have negative effects on the aquatic environment.

An integrated metabolomics and proteogenomics approach reveals molecular alterations following carbamazepine exposure in the male mussel Mytilus galloprovincialis

Carbamazepine is one of the most abundant pharmaceutical active compounds detected in aquatic systems. Based on laboratory exposures, carbamazepine has been proven to adversely affect aquatic organisms. However, the underlying molecular events remain poorly understood. This study aims to investigate the molecular mechanisms potentially associated with toxicological effects of carbamazepine on the mussel Mytilus galloprovincialis exposed for 3 days at realistic concentrations encountered in coastal environments (80 ng/L and 8 μg/L). An integrated metabolomics and proteogenomics approach, including data fusion strategy, was applied to gain more insight in molecular events and cellular processes triggered by carbamazepine exposure. Consistent metabolic and protein signatures revealed a metabolic rewiring and cellular stress at both concentrations (e.g. intensification of protein synthesis, transport and catabolism processes, disruption of lipid and amino acid metabolisms). These highlighted molecular signatures point to the induction of autophagy, closely related with carbamazepine mechanism of action, as well as a destabilization of the lysosomal membranes and an enzymatic overactivity of the peroxisomes. Induction of programmed cell death was highlighted by the modulation of apoptotic cognate proteins. The proposed integrative omics data analysis was shown to be highly relevant to identify the modulations of the two molecular levels, i.e. metabolites and proteins. Multi-omics approach is able to explain the resulting complex biological system, and document stronger toxicological pieces of evidence on pharmaceutical active compounds at environmental concentrations in sentinel organisms.

Variability of metabolic, protective, antioxidant, and lysosomal gene transcriptional profiles and microbiota composition of Mytilus galloprovincialis farmed in the North Adriatic Sea (Italy)

This study evaluates the transcriptional profiles of genes related to physiological responses in digestive glands (DG) of Mytilus galloprovincialis under the influence of seasonal changes of environmental variables, gender bias, and gonadal development. Composition of the DG microbiome was also explored. Mussels were collected across 7 months encompassing 3 seasons from a farm in the Northwestern Adriatic Sea. All gene products showed complex transcriptional patterns across seasons. Salinity, surface oxygen and transparency significantly correlate with transcriptional profiles of males, whereas in females temperature and gonadal maturation mostly explained the observed transcriptional changes. Seasonal variations and gender-specific differences were observed in DG microbiome composition, with variations resembling metabolic accommodations likely facing season progression and reproductive cycle. Results provide baseline information to improve actual monitoring strategies of mussel farming conditions and forecast potential detrimental impacts of climatological/environmental changes in the study area.

Differential Expression of Long Non-Coding RNA (lncRNA) in Mediterranean Mussel (Mytilus galloprovincialis) Hemocytes under Immune Stimuli

The Mediterranean mussel is one of the most economically relevant bivalve mollusk species in Europe and China. The absence of massive mortalities and their resistance to pathogens affecting other cultured bivalves has been under study in recent years. The transcriptome response of this species to different immune stimuli has been extensively studied, and even the complexity of its genome, which has recently been sequenced, has been suggested as one of the factors contributing to this resistance. However, studies concerning the non-coding RNA profiles remain practically unexplored-especially those corresponding to the lncRNAs. To the best of our knowledge, this is the second characterization and study of lncRNAs in this bivalve species. In this work, we identified the potential repertoire of lncRNAs expressed in mussel hemocytes, and using RNA-Seq we analyzed the lncRNA profile of mussel hemocytes stimulated in vitro with three different immune stimuli: LPS, poly I:C, and β-glucans. Compared to unstimulated hemocytes, LPS induced the highest modulation of lncRNAs, whereas poly I:C and β-glucans induced a similar discrete response. Based on the potential cis-regulatory activity of the lncRNAs, we identified the neighboring protein-coding genes of the regulated lncRNAs to estimate-at least partially-the processes in which they are implicated. After applying correlation analyses, it seems that-especially for LPS-the lncRNAs could participate in the regulation of gene expression, and substantially contribute to the immune response.

Treatment with ascorbic acid normalizes the aerobic capacity, antioxidant defence, and cell death pathways in thermally stressed Mytilus galloprovincialis

Considering temperature's upcoming increase due to climate change, combined with the fact that Mediterranean mussels Mytilus galloprovincialis (Lamarck, 1819) live at their upper limits [critical temperatures (Tc) beyond 25 °C], we cannot be sure of this species' sustainable future in the Mediterranean Sea. Deviation from optimum temperatures leads to cellular damage due to oxidative stress. Although ascorbic acid (AA) is a major scavenger of reactive oxygen species (ROS), its capacity to minimize oxidative stress effects is scarcely studied in aquatic organisms. Thus, treatment with 5 mM and 10 mM AA of thermally stressed molluscs had been employed in order to examine its antioxidant capacity. While 5 mM had no effect, 10 mM normalized COX1 and ND2 relative mRNA levels, and superoxide dismutase (SOD), catalase, and glutathione reductase (GR) enzymatic activity levels in both examined tissues: posterior adductor muscle (PAM) and mantle. ATP levels, probably providing the adequate energy for antioxidant defence in thermally stressed mussels, is also normalized under 10 mM AA treatment. Moreover, autophagic indicators such as LC3 II/I and SQSTM1/p62 levels are normalized, indicating autophagy amelioration. Apoptosis also seems to be inhibited since both Bax/Bcl-2 and cleaved caspase substrate levels decrease with 10 mM AA treatment. Therefore, treatment of mussels with AA seems to produce threshold effects, although the precise underlying mechanisms must be elucidated in future studies. These findings show that treatment of mussels with effective antioxidants can be useful as a strategic approach for the reduction of the deleterious effects on mussels' summer mortality in aquaculture zones.

Toxicity of gamma aluminium oxide nanoparticles in the Mediterranean mussel (Mytilus galloprovincialis): histopathological alterations and antioxidant responses in the gill and digestive gland

PURPOSE

Accumulation of Gamma aluminium oxide nanoparticles γ-Al₂O₃ NPs significant impact on aquatic ecosystems. However, the toxicity of γ-Al₂O₃ NPs in aquatic organisms has been limited investigated. This study investigated histopathological changes and antioxidant responses induced by different concentrations of γ-Al₂O₃ NPs in Mytilus galloprovincialis.

MATERIAL AND METHODS

In this study, mussels were exposed to different concentrations of 5 nm γ-Al₂O₃ NPs (0, 5, 20 and 40 mg/L) for 96 h under controlled laboratory conditions. Gill and digestive gland from mussels were assessed to histopathological (light microscopy, histopathological condition indices, digestive gland tubule types), SOD, CAT, GPx activities.

RESULTS

Histopathological indices calculated higher, and significantly different in all exposure groups compared to the control group in gill and digestive gland (p < 0.05). Atrophic phase tubules proportion very high in 20 and 40 mg/L γ-Al₂O₃ NPs exposure groups. No significant changes in CAT activities in the gill and digestive gland (p > 0.05). Superoxide dismutase (SOD) activities significantly different (p ≤ 0.05) in the digestive gland from 20 mg/L γ-Al₂O₃ NPs exposures, and GPx activities significantly different (p < 0.05) in gill from 40 mg/L γ-Al₂O₃ NPs exposures.

CONCLUSION

These results indicate that contamination of γ-Al₂O₃ NPs negatively affects the aquatic organism.

Tissue-scale microbiota of the Mediterranean mussel (Mytilus galloprovincialis) and its relationship with the environment

In this study, we characterize the structural variation of the microbiota of Mytilus galloprovincialis at the tissue scale, also exploring the connection with the microbial ecosystem of the surrounding water. Mussels were sampled within a farm located in the North-Western Adriatic Sea and microbiota composition was analyzed in gills, hemolymph, digestive glands, stomach and foot by Next Generation Sequencing marker gene approach. Mussels showed a distinctive microbiota structure, with specific declinations at the tissue level. Indeed, each tissue is characterized by a distinct pattern of dominant families, reflecting a peculiar adaptation to the respective tissue niche. For instance, the microbiota of the digestive gland is characterized by Ruminococcaceae and Lachnospiraceae, being shaped to ferment complex polysaccharides of dietary origin into short-chain fatty acids, well matching the general asset of the animal gut microbiota. Conversely, the gill and hemolymph ecosystems are dominated by marine microorganisms with aerobic oxidative metabolism, consistent with the role played by these tissues as an interface with the external environment. Our findings highlight the putative importance of mussel microbiota for different aspects of host physiology, with ultimate repercussions on mussel health and productivity.

Parasite Load and STRs Genotyping of Toxoplasma gondii Isolates From Mediterranean Mussels (Mytilus galloprovincialis) in Southern Italy

Toxoplasmosis is a zoonotic food-borne disease caused by Toxoplasma gondii, a land-derived protozoan parasite that infects a broad range of terrestrial and aquatic hosts. T. gondii may reach coastal waters via contaminated freshwater runoff and its oocysts may enter into the marine food web. Marine invertebrates as mussels being filter feeders are exposed and may concentrate T. gondii oocysts representing a potential source of infection for animals and humans. The present works investigated the prevalence, parasite burden and genotypes of T. gondii in the Mediterranean mussels (Mytilus galloprovincialis) from southern Italy. We sampled a total of 382 individual Mediterranean mussels from May to August 2018 from seven production sites in the Gulf of Naples (Campania region). An additional sample including 27 farmed Mediterranean mussels was obtained in February 2018 from a mollusk depuration plant in Corigliano Calabro (Calabria region). T. gondii DNA was detected in 43 out of 409 (10.5%) Mediterranean mussels from seven out of eight sampling sites. The number of T. gondii copies/g in the digestive gland ranged from 0.14 to 1.18. Fragment analysis of Short Tandem Repeats (STRs) at 5 microsatellite loci was performed from 10 T. gondii PCR positive samples revealing the presence of five distinct genotypes including one corresponding to type I and four atypical genotypes. These findings suggest potential implications of epidemiological importance for human and animal health because both type I and atypical genotypes could be highly pathogenic.

Mytilus galloprovincialis CYP1A-like mRNAs reveal closer proximity of mytilid CYP1A to the eumetazoan CYP2 family

Due to the role of Cytochrome P450, Family 1, Subfamily A (CYP1A) in the detoxification of many polycyclic aromatic hydrocarbons (PAHs), there has been an effort to characterise the gene and the products from its expression in organisms that are relevant for biomonitoring and toxicity testing procedures. Nonetheless, the existence of functional homologues in aquatic invertebrates is not entirely consensual, especially in bivalve molluscs, which pose as one of the most important models for aquatic toxicologists, especially mytilids. After isolation and sequencing of CYP1A-like mRNA from the Mediterranean mussel, Mytilus galloprovincialis, phylogenetics incorporating homologues from molluscs and other eumetazoans, vertebrates included, yielded notorious similarity to sequences belonging to the CYP2 Family. Altogether, the findings further indicate that CYP1A-like CYPs may be absent in bivalves, in lieu of Families CYP2, 3 and 4, suggesting caution when interpreting data from common biomarkers of exposure to aromatic hydrocarbons that have been developed for CYP1A activity and expression in higher deuterostomes.

Early and efficient induction of antioxidant defense system in Mytilus galloprovincialis embryos exposed to metals and heat stress

The present study aims to elucidate the stress response of early life stages of Mytilus galloprovincialis to the combine effects of selected metals and elevated temperature. For this purpose, we investigated the response of a large panel of oxidative stress markers such as catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) activities and lipid peroxidation (thiobarbituric acid reactive substrates (TBARS) concentration) and metallothionein accumulation (MT) as well as selected gene transcription level and metal accumulation in mussels larvae exposed to a sub-lethal concentration of Cu (9.54µg/L), Ag (2.55µg/L) and mixture of the two metals (Cu (6.67µg/L)+Ag (1.47µg/L)) along with a temperature gradient (18, 20 and 22°C) for 48h. Cu and Ag applied as single or mixture were differentially accumulated in mussel larvae according to the exposure temperature. Sod, cat, gst and mt-10 gene transcription levels showed an important increase in larvae exposed to Cu, Ag or to the mix compared to the control condition at 18°C. The same pattern but with higher induction levels was recorded in larvae co-exposed to metals at 20°C. At 22°C, a significant decrease in mRNA abundance of cat, gst and sod and a significant up-regulation of mts targets (mt10 and mt20) were observed.

RESULTS

suggest that co-exposure to metals and moderate elevated temperature (20 and 22°C) significantly increased the antioxidant enzyme activities of catalase (CAT), and glutathione-S-transferase (GST) and caused an increase of metal and metallothionein concentrations. In contrast, no significant change in lipid peroxidation products measured as TBARS content was observed indicating a protective response of anti-oxidative system. This study provides first evidences of the early and efficient protective response of antioxidant defense mechanisms in mussel's early life stages facing in multi stressors situations.

High sensitivity of embryo-larval stage of the Mediterranean mussel, Mytilus galloprovincialis to metal pollution in combination with temperature increase

The present work aimed to assess the effects of two widespread metallic pollutants, copper and silver, along with environmentally-realistic temperature increases, on embryo-larval development of the Mediterranean mussel Mytilus galloprovincialis. First, mussel embryos upon fertilization were exposed for 48 h to increasing concentrations of Cu (0.5-500 μg/L) and Ag (0.1-100 μg/L) at different temperatures (18, 20, 22 or 24 °C) in order to characterize toxicity of each toxicant at the different tested temperatures. Increasing concentrations of a Cu-Ag mixture were then tested in order to assess the mixture effect at different temperatures (18, 20 or 22 °C). Embryotoxicity was measured after 48 h of exposure (D-larvae stage) considering both the percentage of abnormalities and developmental arrest in D-larvae. The results suggest that the optimum temperature for mussel larvae development is 18 °C (12.65± 1.6% malformations) and beyond 20 °C a steep increase of abnormal larvae was observed up to 100% at 24 °C. Ag was more toxic than Cu with a 50% effective concentration (EC50) at 18 °C of 6.58 μg/L and 17.6 μg/L, respectively. Temperature increased the toxicity of both metals as proved with the EC50 at 20 °C at 3.86 μg/L and 16.28 μg/L for Ag and Cu respectively. Toxic unit calculation suggests additive effects of Cu and Ag in mixture at 18 and 20 °C. These results highlight a possible impairment of M. galloprovincialis reproduction in the Mediterranean Sea in relation to increase of both pollutants and water temperature due to global warming.

Assessment of pollution in the Bizerte lagoon (Tunisia) by the combined use of chemical and biochemical markers in mussels, Mytilus galloprovincialis

In order to assess the environmental quality of the Bizerte lagoon (Tunisia), biomarker and contaminant levels were measured in Mediterranean mussels (Mytilus galloprovincialis) from five selected sites. Persistent organic pollutants (POPs) were quantified in whole body and enzyme activities such as acetylcholinesterase (AChE), catalase (CAT) and glutathione S-transferase (GST) in gills. Despite the relatively low levels of organic contaminants, the selected biomarkers responded differently according to the pollution level at the different sites. GST and AChE activities were correlated with the amount of DDTs in mussel tissues. These two enzymatic activities were also correlated to temperature and pH. No significant difference was observed for CAT activity. Principal component analysis showed a clear separation of sampling sites in three different assemblages which is consistent with POP body burden in mussels. Our results confirmed the usefulness of combining biomarker and chemical analyses in mussels to assess chemical pollution in the Bizerte lagoon.

Differential ABCB and ABCC gene expression and efflux activities in gills and hemocytes of Mytilus galloprovincialis and their involvement in cadmium response

The aim of the study was to characterize ABC transport proteins gene expression and efflux activities in gills and hemocytes of the Mediterranean mussel and to evaluate their response to Cd. At basal level a higher expression of abcb-like gene was observed in gills than in hemocytes while abcc-like gene showed similar levels. Both P-gp and MRPs inhibitors (cyclosporine and MK571) blocked efflux activities in gills; hemocytes were sensitive only to MK571. After 120 min in vitro pre-exposure to CdCl2, the efflux activity increased significantly in gills and hemocytes. In vivo exposure to CdCl2 (0.4 μM) increased abcb-like gene expression in gills without affecting efflux activity. In hemocytes abcc-like gene resulted up-regulated and Ca-AM efflux resulted enhanced. An increased uptake of Cd in gills biopsies was observed in the presence of both P-gp and MRPs inhibitors. Our results indicate that ABC transporters seem involved in the first protective response to Cd and this response is tissue-specific.