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Mussels, which occupy important positions in marine ecosystems, attach tightly to underwater substrates using a proteinaceous holdfast known as the byssus, which is tough, durable, and resistant to enzymatic degradation. Although various byssal proteins have been identified, the mechanisms by which it achieves such durability are unknown. Here we report comprehensive identification of genes involved in byssus formation through whole-genome and foot-specific transcriptomic analyses of the green mussel, Perna viridis . Interestingly, proteins encoded by highly expressed genes include proteinase inhibitors and defense proteins, including lysozyme and lectins, in addition to structural proteins and protein modification enzymes that probably catalyze polymerization and insolubilization. This assemblage of structural and protective molecules constitutes a multi-pronged strategy to render the byssus highly resistant to environmental insults.

This study evaluated the toxicity of cadmium (Cd) on the green mussel Perna viridis, aiming to identify toxicological endpoints and investigate its responses across physiological, bioenergetic, and biochemical parameters. The 96-hour LC50 value for Cd in P. viridis was 3.03 ± 0.12 mg L−1, with a 95% confidence interval of 2.35–3.91 mg L−1. Chronic toxicity tests revealed a No Observable Effect Concentration (NOEC), Lowest Observable Effect Concentration (LOEC), and chronic toxicity values of 0.20, 0.37, and 0.29 mg L−1, respectively. Cadmium accumulation in treated mussels increased 46- to 215-fold compared to the control group. Superoxide dismutase, catalase, glutathione S-transferase, and glutathione peroxidase levels in exposed mussels exhibited a significant increase compared to the control group. The redox index ratio, acetylcholinesterase activity, and lysosomal membrane stability decreased with increasing exposure concentrations. Levels of reduced and oxidized glutathione, glutathione reductase, lipid peroxidation, and metallothionein-like proteins increased in exposed mussels. Clearance rate, respiration rate, and excretion rate decreased in a dose-dependent manner. Protein, carbohydrate, and lipid levels decreased with increasing exposure concentration (p < 0.001). Mitochondrial electron transport system activity increased, while cellular energy allocation (p < 0.001) and scope for growth decreased in a dose-dependent manner (p < 0.01). The significant increase in antioxidants suggests heightened oxidative stress in mussels under Cd exposure. The physiological activities of the mussels were severely affected, ultimately leading to a reduced scope for growth. The toxicological data generated in this study contribute to the development of seawater quality criteria for the metal Cd.

The Byssus, which is derived from the foot gland of mussels, has been proved to bind heavy metals effectively, but few studies have focused on the molecular mechanisms behind the accumulation of heavy metals by the byssus. In this study, we integrated high-throughput transcriptome and proteome sequencing to construct a comprehensive protein database for the byssus of Chinese green mussel (Perna viridis), aiming at providing novel insights into the molecular mechanisms by which the byssus binds to heavy metals. Illumina transcriptome sequencing generated a total of 55,670,668 reads. After filtration, we obtained 53,047,718 clean reads and subjected them to de novo assembly using Trinity software. Finally, we annotated 73,264 unigenes and predicted a total of 34,298 protein coding sequences. Moreover, byssal samples were analyzed by proteome sequencing, with the translated protein database from the foot transcriptome as the reference for further prediction of byssal proteins. We eventually determined 187 protein sequences in the byssus, of which 181 proteins are reported for the first time. Interestingly, we observed that many of these byssal proteins are rich in histidine or cysteine residues, which may contribute to the byssal accumulation of heavy metals. Finally, we picked one representative protein, Pvfp-5-1, for recombinant protein synthesis and experimental verification of its efficient binding to cadmium (Cd2+) ions.

Since 1995, the spread of the green mussel Perna viridis (L.) along the South American coast has raised concerns about its potential impacts on coastal communities in vulnerable areas. This study presents updated records of P. viridis along the Brazilian coast and assesses its presence within marine protected areas. Species identification was based on periostracum coloration and mantle papillae morphology, effectively distinguishing P. viridis from the native congener Perna perna (L.). Its presence in lagoon complexes poses significant challenges for the conservation of native species and maintenance of regional biodiversity. We stress the need to assess the balance between predators, parasites, and other ecological components in invaded areas to mitigate the impacts on regional ecology. In-depth studies on the population dynamics of P. viridis must be conducted, assessing nutrient levels in restricted environments and factors influencing the species’ attachment to different substrates. Our findings highlight the urgency of implementing effective management strategies and adaptive conservation policies to address the invasion of P. viridis . These policies should focus on preventing further spreading of the species and supporting the sustainability of local estuarine and coastal ecosystems.

Three classes of mussel, the invasive Mytilus galloprovincialis and 2 genetic lineages of the indigenous Perna perna, show partially overlapping distributions along a large-scale temperature gradient in South Africa. We asked whether their physiological tolerances explain their distributional limits, investigating the effects of acute temperature change on heart rate, oxygen consumption and anaerobic end-product accumulation in air and water in the laboratory. For all 3 classes, heart rate and oxygen consumption were significantly reduced in air and were not correlated with temperature. During immersion, temperature had powerful effects on metabolic rate, but the ranking of heart rates reversed between heat and cold stress. The eastern P. perna lineage had higher heart rates with rising temperatures, while M. galloprovincialis showed higher heart rates during cooling. Despite no difference in upper thermal limits among mussel classes, their Arrhenius activation energies differed significantly, in parallel with their warm to cool distributions in the order P. perna east > P. perna west > M. galloprovincialis. The results indicate that the eastern lineage of P. perna is better adapted to warm temperatures and M. galloprovincialis is better adapted to high shore conditions. Upper thermal limits gave only a crude approximation of the effects of temperature stress. Although the thermal limits of these populations were similar, their overall responses to stress differed markedly, reflecting their distributions and potentially affecting their competitive interactions. We suggest that thermal limits offer poor explanations for species distributions, and highlight the critical importance of both sub-lethal effects and sub-specific differences in physiology.

Oceanographic features shape the distributional and genetic patterns of marine species by interrupting or promoting connections among populations. Although general patterns commonly arise, distributional ranges and genetic structure are species-specific and do not always comply with the expected trends. By applying a multimarker genetic approach combined with Lagrangian particle simulations (LPS) we tested the hypothesis that oceanographic features along northeastern Atlantic and Mediterranean shores influence dispersal potential and genetic structure of the intertidal mussel Perna perna. Additionally, by performing environmental niche modelling we assessed the potential and realized niche of P. perna along its entire native distributional range and the environmental factors that best explain its realized distribution. Perna perna showed evidence of panmixia across > 4,000 km despite several oceanographic breaking points detected by LPS. This is probably the result of a combination of life history traits, continuous habitat availability and stepping-stone dynamics. Moreover, the niche modelling framework depicted minimum sea surface temperatures (SST) as the major factor shaping P. perna distributional range limits along its native areas. Forthcoming warming SST is expected to further change these limits and allow the species to expand its range polewards though this may be accompanied by retreat from warmer areas.

Increasing seawater temperatures coupled with more intense and frequent heatwaves pose an increasing threat to marine species. In this study, the New Zealand green-lipped mussel, Perna canaliculus , was used to investigate the effect of genetics and ontogeny on thermal resilience. The culturally and economically significant mussel P. canaliculus (Gmelin, 1971) has been selectively-bred in New Zealand for two decades, making it a unique biological resource to investigate genetic interactions in a temperate bivalve species. Six selectively-bred full sibling families and four different ages, from early juveniles (6, 8, 10 weeks post-fertilisation) to sub-adults (52 weeks post-fertilisation), were used for experimentation. At each age, each family was exposed to a three-hour heat challenge, followed by recovery, and survival assessments. The shell lengths of live and dead juvenile mussels were also measured. Gill tissue samples from sub-adults were collected after the thermal challenge to quantify the 70 kDa heat shock protein gene ( hsp70 ). Results showed that genetics, ontogeny and size influence thermal resilience in P. canaliculus , with LT 50 values ranging between 31.3 and 34.4 °C for all studied families and ages. Juveniles showed greater thermotolerance compared to sub-adults, while the largest individuals within each family/age class tended to be more heat sensitive than their siblings. Sub-adults differentially upregulated hsp70 in a pattern that correlated with net family survival following heat challenge, reinforcing the perceived role of inducible HSP70 protein in molluscs. This study provides insights into the complex interactions of age and genotype in determining heat tolerance of a key mussel species. As marine temperatures increase, equally complex selection pressure responses may therefore occur. Future research should focus on transcriptomic and genomic approaches for key species such as P. canaliculus to further understand and predict the effect of genetic variation and ontogeny on their survival in the context of climate change.

The study assesses the effects of carbon dioxide capture and storage (CCS) leaks and ocean acidification (OA) on the metal bioavailability and reproduction of the mytilid Perna perna . In laboratory-scale experiments, CCS leakage scenarios (pH 7.0, 6.5, 6.0) and one OA (pH 7.6) scenario were tested using metal-contaminated sediment elutriates and seawater from Santos Bay. The OA treatment did not have an effect on fertilisation, while significant effects were observed in larval-development bioassays where only 16 to 27 % of larva developed normally. In treatments that simulated CO 2 leaks, when compared with control, fertilisation success gradually decreased and no larva developed to the D-shaped stage. A fall in pH increased the bioavailability of metals to marine mussels. Larva shell size was significantly affected by both elutriates when compared with seawater; moreover, a significant difference occurred at pH 6.5 between elutriates in the fertilisation bioassay.

Mussels, particularly Indian brown mussels ( Perna perna L.), have great ecological and economic value due to their restricted distribution along the Indian coastline. They are ideal model organisms for various study domains such as climate change adaptability, biomonitoring, biomaterials, bioadhesion, biofouling, and antifouling. However, there is a noticeable scarcity of genetic information about this species. There is no previous transcriptomic study of the Indian brown mussel. This study used a de novo transcriptomic technique to generate a mussel foot-specific transcriptome for P. perna using 31.72 million high-quality Illumina paired-end reads. A total of 33,567 unigenes were generated, and 18,951 coding sequences (CDS) were predicted. We identified several gene families and key functional genes, including Cytochrome P450 ( CYP2 , CYP1 , CYP3, CYP4 ), Heat-shock proteins ( HSP-70, HSP-90 ), Superoxide dismutase ( SOD ), Catalase ( CAT ), Glutathione-S transferase ( GST ), Toll-like receptors ( TLR-13, TLR-8, TLR-7 ), Aquaporins ( AQP-4, AQP-8 ), growth factor ( IGF ), Glutathione peroxidase, Acetylcholinesterase ( AchE ), Hypoxia-inducible factor-2 and proteins and enzymes involved in bio-adhesion. Our current study serves as a platform for future functional and comparative transcriptomics studies.

The specific status of the brown mussel, Perna indica, in southern India and northern Sri Lanka has long been questioned. Its limited geographical distribution within the extensive range of the Asian green mussel, P. viridis, and its morphometric similarity to the African brown mussel, P. perna, have led several authorities to suggest that P. indica is not a distinct species but is in fact introduced P. perna. Analysis of DNA sequences for nuclear ITS and mitochondrial COI sequence data from newly collected mussels from southern India examined in the context of data from GenBank for mussels of the genus Perna reveals that P. indica is indeed P. perna from the Oman region. A literature review indicates that P. indica (now P. perna) has been established in southern India for at least 100 years. Reports of ecological interactions between the native P. viridis and the introduced P. perna reveal that P. perna grows to a larger size than P. viridis and outcompetes the native mussel. P. perna forms high density populations that have long been fished by local coastal communities and recently the fishery for P. perna has expanded to markets beyond the coastal area. Eradication of the introduced P. perna is not feasible and is not desirable given its important role as a source of protein and revenue for the local community. Because no monitoring of the range of P. perna in southern India occurs it is not possible to know if this species is increasing its area of distribution, but a qualitative assessment of ongoing range expansion is made based on limited evidence from published reports. The possibility exists for inter-specific hybridisation between P. viridis and P. perna and we recommend that testing commence to check for this. This research highlights the value of a detailed understanding of the genetic structure (four different clades) of the genus Perna, without which the status of P. indica as P. perna from Oman in southern India could not have been made.