Characterization of the transcriptional effects of the plastic additive dibutyl phthalate alone and in combination with microplastic on the green-lipped mussel Perna canaliculus.

The presence and persistence of microplastics (MPs) in diverse aquatic environments are of global concern. Microplastics can impact marine organisms via direct physical interaction and the release of potentially harmful chemical additives incorporated into the plastic. These chemicals are physically bound to the plastic matrix and can leach out. The hazards associated with chemical additives to exposed organisms is not well characterized. We investigated the hazards of plastic additives leaching from plastic. We used the common plasticizer dibutyl phthalate (DBP) as a chemical additive proxy and the New Zealand green-lipped mussel (Perna canaliculus) as a model. We used early-adult P. canaliculus exposed to combinations of virgin and DBP-spiked polyvinyl chloride (PVC), MPs, and DBP alone for 7 days. Whole transcriptome sequencing (RNA-seq) was conducted to assess whether leaching of DBP from MPs poses a hazard. The differences between groups were evaluated using pairwise permutational multivariate analysis of variance (PERMANOVA), and all treatments were significantly different from controls. In addition, a significant difference was seen between DBP and PVC MP treatment. Transcriptome analysis revealed that mussels exposed to DBP alone had the most differentially expressed genes (914), followed by PVC MP + DBP (448), and PVC MP (250). Gene ontology functional analysis revealed that the most enriched pathway types were in cellular metabolism, immune response, and endocrine disruption. Microplastic treatments enriched numerous pathways related to cellular metabolism and immune response. The combined exposure of PVC MP + DBP appears to cause combined effects, suggesting that DBP is bioavailable to the exposed mussels in the PVC MP + DBP treatment. Our results support the hypothesis that chemical additives are potentially an important driver of MP toxicity. Environ Toxicol Chem 2024;43:1604-1614. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Size-dependent effects of microplastics on intestinal microbiome for Perna viridis.

Microplastics pollution threatens to marine organisms, particularly bivalves that actively ingest and accumulate microplastics of certain sizes, potentially disrupting intestinal homeostasis. This study investigated the microplastic abundance in wild and farmed mussels around Singapore, and examined the size-dependent effects of nano- to micro-scale polystyrene (0.5 µm/5 µm/50 µm) on the mussel intestinal microbiome in the laboratory. The field investigation revealed higher microplastic abundance in farmed mussels compared to wild ones. Experimentally, mussels exposed to 0.6 mg/L of microplastics for 7 days, followed by a 7-day depuration period, showed substantial impacts on Spirochaetes and Proteobacteria, facilitating the proliferation of pathogenic species and differentially affecting their pathogenic contributions. Metagenomics analysis revealed that microplastic exposure reduced Spirochaeta's contribution to virulence and pathogenicity loss, did not affect Vibrio and Oceanispirochaeta's pathogenicity, and increased Treponema and Oceanispirochaeta's contributions to pathogenicity loss. Moreover, microplastics increased transmembrane transporters and impacted oxidative phosphorylation enzymes, impairing energy metabolism. These effects persisted after depuration, indicating lack of resilience in the microbiome. Nano- and micro-scale plastics perturbed the mussel microbiome composition and functions in a size-dependent manner, with nano-plastics being the most disruptive. The increasing use and sale of aquaculture equipment of plastic may exacerbate the intestinal dysbiosis in bivalves, which threatens consumers' health.

Physiological and biochemical response in green mussel Perna viridis subjected to continuous chlorination: Perspective on cooling water discharge criteria.

Heavy infestation by Perna viridis has been observed in the sub-seabed seawater intake tunnel and CWS of a tropical coastal power station in-spite of continuous low dose chlorination regime (0.2 ± 0.1 mg L-1) (CLDC), indicating periodical settlement and growth. Continuous arrival of mussels (colonized in the sub seabed tunnel intake section) at the pump house indicated that the mussels were able to tolerate and survive in a chlorinated environment, for varying time periods and were dislodged when they become weak and subsequent death, leading to flushing out of the system. In the present study, effect of continuous chlorination [0.2 mg L-1 (in-plant use); 0.5 mg L-1 (shock dose) & 1.0 mg L-1 (high levels)] was evaluated on mussels to assess; (a) time taken for mortality, (b) action of chlorine on physiological, genetic, metabolic and neuronal processes. 100% mortality of mussels was observed after 15 (0.2 mg L-1); 9 (0.5 mg L-1) and 6 days (1.0 mg L-1) respectively. Extended valve closure due to chlorination resulted in stress, impairing the respiratory and feeding behavior leading to deterioration in mussel health. Pseudofaeces excretion reduced to 68% (0.2 mg L-1); 10% (0.5 mg L-1) and 89% (1.0 mg L-1) compared to controls. Genotoxicity was observed with increase in % tail DNA fraction in all treatments such as 86% (0.2 mg L-1); 76% (0.5 mg L-1) and 85% (1.0 mg L-1). Reactive Oxygen Species (ROS) stress biomarkers increased drastically/peaked within the first 3 days of continuous chlorination with subsequent quenching by antioxidant enzymes. Gill produced highest generation of ROS; 38% (0.2 mg L-1); 97% (0.5 mg L-1); 98% (1.0 mg L-1). Additionally, it was shown that 84% (0.2 mg L-1), 72% (0.5 mg L-1), and 80.4% (1.0 mg L-1) of the neurotransmitter acetylcholinesterase activity was inhibited by chlorine at the nerve synapse. The cumulative impact of ROS generation, neuronal toxicity, and disrupted functions weakens the overall health of green mussels resulting in mortality.

Bioaccumulation of pollutants in the green-lipped mussel Perna viridis: Assessing pollution abatement in Victoria Harbour and its adjacent aquaculture area, Hong Kong, and the minimal human health risks from mussel consumption.

The green-lipped mussel Perna viridis was utilised for pollution biomonitoring in Victoria Harbour and its adjacent aquaculture area in Hong Kong. P. viridis was collected from a reference site and redeployed at five study sites for five weeks during the dry and wet seasons of 2019. Our study found various polycyclic aromatic hydrocarbons (PAHs) and heavy metals in the mussel tissue, while polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were not detected. P. viridis at the reference site generally displayed lower levels of pollutants. Comparing with previous research in the 1980s and 2000s, we observed substantial reduction in the tissue levels of PAHs, PCBs, OCPs and heavy metals in P. viridis. The human health risks associated with consuming these mussels were determined to be insignificant. Our findings imply that the Harbour Area Treatment Scheme has been effective in improving the water quality in Victoria Harbour and its adjacent aquaculture area.

Nano-scale and micron-scale plastics amplify the bioaccumulation of benzophenone-3 and ciprofloxacin, as well as their co-exposure effect on disturbing the antioxidant defense system in mussels, Perna viridis.

Plastics ranging from nano-scale to micron-scale are frequently ingested by many marine animals. These particles exhibit biotoxicity and additionally perform as vectors that convey and amass adsorbed chemicals within organisms. Meanwhile, the frequency of detection of the benzophenone-3 and ciprofloxacin can be adsorbed on plastic particles, then accumulated in bivalves, causing biotoxicity. To understand their unknown accumulative kinetics in vivo affected by different plastic sizes and toxic effect from co-exposure, several scenarios were set up in which the mode organism were exposed to 0.6 mg/L of polystyrene carrying benzophenone-3 and ciprofloxacin in three sizes (300 nm, 38 µm, and 0.6 mm). The live Asian green mussels were chosen as mode organism for exposure experiments, in which they were exposed to environments with plastics of different sizes laden with benzophenone-3 and ciprofloxacin, then depurated for 7 days. The bioaccumulation and depuration kinetics of benzophenone-3 and ciprofloxacin were measured using HPLC-MS/MS after one week of exposure and depuration. Meanwhile, their toxic effect were investigated by measuring the changes in six biomarkers (condition index, reactive oxygen species, catalase, glutathione, lipid peroxidation, cytochrome P450 and DNA damage). The bioconcentration factors in mussels under different exposure conditions were 41.48-111.75 for benzophenone-3 and 6.45 to 12.35 for ciprofloxacin. The results suggested that microplastics and nanoplastics can act as carriers to increase bioaccumulation and toxicity of adsorbates in mussels in a size-dependent manner. Overproduction of reactive oxygen species caused by microplastics and nanoplastics led to increased DNA damage, lipid peroxidation, and changes in antioxidant enzymes and non-enzymatic antioxidants during exposure. Marked disruption of antioxidant defenses and genotoxic effects in mussels during depuration indicated impaired recovery. Compared to micron-scale plastic with sizes over a hundred micrometers that had little effect on bivalve bioaccumulation and toxicity, nano-scale plastic greatly enhanced the biotoxicity effect.

Interactive effects of elevated temperature and Photobacterium swingsii infection on the survival and immune response of marine mussels (Perna canaliculus): A summer mortality scenario.

The New Zealand Greenshell™ mussel (Perna canaliculus) is an economically important aquaculture species. Prolonged increases in seawater temperature above mussel thermotolerance ranges pose a significant threat to mussel survival and health, potentially increasing susceptibility to bacterial infections. Using challenge experiments, this study examined the combined effects of increased seawater temperature and bacterial (Photobacterium swingsii) infection on animal survival, haemocyte and biochemical responses of adult mussels. Mussels maintained at three temperatures (16, 20 and 24 °C) for seven days were either not injected (control), injected with sterile marine broth (injection control) or P. swingsii (challenged with medium and high doses) and monitored daily for five days. Haemolymph and tissue samples were collected at 24, 48, 72, 96, 120 h post-challenge and analysed to quantify bacterial colonies, haemocyte responses and biochemical responses. Mussels infected with P. swingsii exhibited mortalities at 20 and 24 °C, likely due to a compromised immune system, but no mortalities were observed when temperature was the only stressor. Bacterial colony counts in haemolymph decreased over time, suggesting bacterial clearance followed by the activation of immune signalling pathways. Total haemocyte counts and viability data supports haemocyte defence functions being stimulated in the presence of high pathogen loads at 24 °C. In the gill tissue, oxidative stress responses, measured as total antioxidant capacity and malondialdehyde (MDA) levels, were higher in infected mussels (compared to the controls) after 24h and 120h post-challenge at the lowest (16 °C) and highest temperatures (24 °C), indicating the presence of oxidative stress due to temperature and pathogen stressors. Overall, this work confirms that Photobacterium swingsii is pathogenic to P. canaliculus and indicates that mussels may be more vulnerable to bacterial pathogens under conditions of elevated temperature, such as those predicted under future climate change scenarios.

Oxidation and cross-link of tyrosine-rich proteins are involved in the periostracum formation of the green mussel Perna viridis (Linnaeus).

Ocean acidification causes severe shell dissolution and threats the survival of marine molluscs. The periostracum in molluscs consists of macromolecules such as proteins and polysaccharides, and protects the inner shell layers from dissolution and microbial erosion. Moreover, it serves as the primary template for shell deposition. However, the chemical composition and formation mechanism of the periostracum is largely unknown. In this study, we applied transcriptomic, proteomics, physical, and chemical analysis to unravel the mysteries of the periostracum formation in the green mussel Perna viridis Linnaeus. FTIR analysis showed that the periostracum layer was an organic membrane mainly composed of polysaccharides, lipids, and proteins, similar to that of the shell matrix. Interestingly, the proteomic study identified components enriched in tyrosine and some enzymes that evolved in tyrosine oxidation, indicating that tyrosine oxidation might play an essential role in the periostracum formation. Moreover, comparative transcriptomics suggested that tyrosine-rich proteins were intensively synthesized in the periostracum groove. After being secreted, the periostracum proteins were gradually tanned by oxidation in the seawater, and the level of crosslink increased significantly as revealed by the ATR-FTIR. Our present study sheds light on the chemical composition and putative tanning mechanism of the periostracum layer in bivalve molluscs. SIGNIFICANCE: The periostracum layer, plays an essential role in the initiation of shell biomineralization, the protection of minerals from dissolution for molluscs and especially ocean acidification conditions in the changing global climate. However, the molecular mechanism underlying the periostracum formation is not fully understood. In this study, we revealed that the oxidation and cross-link of tyrosine-rich proteins by tyrosinase are involved in periostracum formation in the green mussel Perna viridis. This study provides some insights into the first step of mussel shell formation and the robust adaptation of P. viridis to diverse habitats. These findings also help to reveal the potential acclimation of bivalves to the projected acidifying seawater.

Quantification of Photobacterium swingsii and characterisation of disease progression in the New Zealand Greenshell™ mussel, Perna canaliculus.

Greenshell™ mussels (Perna canaliculus) are endemic to New Zealand and support the largest aquaculture industry in the country. Photobacterium swingsii was isolated and identified from moribund P. canaliculus mussels following a mass mortality event. In this study, a challenge experiment was used to characterise, detect, and quantify P. swingsii in adult P. canaliculus following pathogen exposure via injection into the adductor muscle. A positive control (heat-killed P. swingsii injection) was included to account for the effects of injection and inactive bacterial exposure. Survival of control and infected mussels remained 100% during 72-hour monitoring period. Haemolymph was sampled for bacterial colony counts and haemocyte flow cytometry analyses; histology sections were obtained and processed for histopathological assessments; and adductor muscle, gill, digestive gland were sampled for quantitative polymerase chain reaction (PCR) analyses, all conducted at 12, 24, 48 h post-challenge (hpc). The most profound effects of bacterial injection on mussels were seen at 48 hpc, where mussel mortality, haemocyte counts and haemolymph bacterial colony forming were the highest. The quantification of P. swingsii via qPCR showed highest levels of bacterial DNA at 12 hpc in the adductor muscle, gill, and digestive gland. Histopathological observations suggested a non-specific inflammatory response in all mussels associated with a general stress response. This study highlights the physiological effects of P. swingsii infection in P. canaliculus mussels and provides histopathological insight into the tissue injury caused by the action of injection into the adductor muscle. The multi-technique methods used in this study can be applied for use in early surveillance programs of bacterial infection on mussel farms.

Gut microbiome resilience of green-lipped mussels, Perna canaliculus, to starvation.

Host gut microbiomes play an important role in animal health and resilience to conditions, such as malnutrition and starvation. These host-microbiome relationships are poorly understood in the marine mussel Perna canaliculus, which experiences significant variations in food quantity and quality in coastal areas. Prolonged starvation may be a contributory factor towards incidences of mass mortalities in farmed mussel populations, resulting in highly variable production costs and unreliable market supplies. Here, we examine the gut microbiota of P. canaliculus in response to starvation and subsequent re-feeding using high-throughput amplicon sequencing of the 16S rRNA gene. Mussels showed no change in bacterial species richness when subjected to a 14-day starvation, followed by re-feeding/recovery. However, beta bacteria diversity revealed significant shifts (PERMANOVA p-value < 0.001) in community structure in the starvation group and no differences in the subsequent recovery group (compared to the control group) once they were re-fed, highlighting their recovery capability and resilience. Phylum-level community profiles revealed an elevation in dominance of Proteobacteria (ANCOM-BC p-value <0.001) and Bacteroidota (ANCOM-BC p-value = 0.04) and lower relative abundance of Cyanobacteria (ANCOM-BC p-value = 0.01) in the starvation group compared to control and recovery groups. The most abundant genus-level shifts revealed relative increases of the heterotroph Halioglobus (p-value < 0.05) and lowered abundances of the autotroph Synechococcus CC9902 in the starvation group. Furthermore, a SparCC correlation network identified co-occurrence of a cluster of genera with elevated relative abundance in the starved mussels that were positively correlated with Synechococcus CC9902. The findings from this work provide the first insights into the effect of starvation on the resilience capacity of Perna canaliculus gut microbiota, which is of central importance to understanding the effect of food variation and limitation in farmed mussels.

In-depth knowledge of the low-temperature hydrothermal synthesis of nanocrystalline hydroxyapatite from waste green mussel shell (Perna Viridis).

ABSTRACTThis study presents the use of a low-temperature hydrothermal method for extracting calcium sources from green mussel shell (P. Viridis) wastes and converting them into synthetic nanosized hydroxyapatite (HA). In this study, raw mussel shells were washed, pulverised, and sieved to start producing a fine calcium carbonate-rich powder. XRD quantitative analysis confirmed that the powder contains 97.6 wt. % aragonite. This powder was then calcined for 5 h at 900 °C to remove water, salt, and mud, yielding a calcium-rich feedstock with major minerals of calcite (68.7 wt.%), portlandite (24.7 wt.%), and minor aragonite (6.5 wt.%). The calcined powders were dissolved in aqueous stock solutions of HNO3 and NH4OH before hydrothermally reacting with phosphoric acid [(NH4)2HPO4], yielding pure, nanoscale (16-18 nm) carbonated HA crystals, according to XRD, FT-IR, and SEM analyses. The use of a low-temperature hydrothermal method for a feedstock powder produced by the calcination of low-cost mussel shell wastes would be a valuable processing approach for the industry's development of large-scale hydroxyapatite nanoparticle production.

Elemental Concentrations in the Shells of the Mussel Perna perna: Discrimination of Origin.

The potential use of elemental concentrations and element:calcium (Ca) ratios as indicators of provenance for bivalve mollusks on the Brazilian coast is evaluated herein for the first time. The approach was applied to shells of the mussel Perna perna (target of extractive fisheries) from geographically close areas but under distinct environmental and anthropogenic influences. Both concentrations of the elements normalized by Ca and the total concentrations can be applied to discriminate the mussels' origin. However, the canonical approach using the total concentrations indicated variations regarding the discriminatory power, and the concentrations of the elements normalized by Ca were more robust in differentiating the provenance of the shells. The origin of mussels was better discriminated by six elementary ratios: Al:Ca, Fe:Ca, K:Ca, Mg:Ca, Mn:Ca and Na:Ca. Thus, monitoring studies aiming to discriminate the origin of P. perna individuals along their distribution based on these elementary ratios of the shell are recommended.

Oxidative response to accumulation of trace metals in tissue of two bivalves, the Asian green mussel Perna viridis and the blood cockle Tegillarca granosa, living in Pattani Bay, Thailand.

OBJECTIVE: Using bivalves to indicate aquatic pollutants was favorable for discerning the negative effects of high levels of metal accumulation in tissue. We investigated the correlation between trace metal accumulation and the tissue oxidative response of two bivalves. METHODS: The Asian green mussel Perna viridis and the blood cockle Tegillarca granosa were sampled along with seawater and sediments from three locations around Pattani Bay, Thailand. Accumulation of nine trace metals (cadmium, cobalt, copper, chromium, nickel, manganese, iron, zinc, and lead) in seawater, sediments, and tissue and the oxidative tissue response were evaluated. Metal bioaccumulation factor, biota-sediment accumulation factor, and histopathology were also indicated. RESULT: The present study found that P. viridis and T. granosa were macroconcentrators and bioaccumulative of cadmium, and their tissue accumulation of cadmium was strongly related to lipid peroxidation activation. Perna viridis exhibited a higher oxidative response than T. granosa, as indicated by malondialdehyde, catalase, and reduced glutathione levels. CONCLUSION: The present study indicated that P. viridis and T. granosa were macroconcentrators and bioaccumulative of cadmium, and their tissue accumulation of cadmium was strongly related to lipid peroxidation activation. Research has shown discernible negative effects of a high level of metal accumulation in tissue, and deformed and damaged tissues were present in the gills, digestive glands, intestines, and feet of P. viridis and T. granosa.

Evaluation of microplastic bioaccumulation capacity of mussel (Perna viridis) and surrounding environment in the North coast of Vietnam.

This study aimed to identify the presence of microplastics in green mussels (Perna viridis), surface seawater, and beach sediment on the North Coast of Vietnam. The average concentration of MPs in mussels was 3.67 ± 1.20 MPs/g wet weight and 25.05 ± 5.36 MPs/individual. Regarding surface seawater and beach sediments, the MPs concentration was found at 88.00 ± 30.88 MPs/L and 4800 ± 1776 MPs/kg dry weight, respectively. The dominant microplastics shape was fragment with the fractions ranging from 69.86 to 82.41 %. In addition, the size distribution of MPs was mostly in the range of smaller than 50 µm and 1-150 µm (34.17 % and 45.62 % in mussels; 29.65 % and 43.20 % in surface seawater and 40.22 % and 39.40 % in beach sediment, respectively). Polyethylene terephthalate was the major polymer types 49.93-58.44 % of the detected MPs. The risk assessment results based on the polymer types indicated a warning level in several sites.

Assessment of toxic trace elements (Cd, Pb, As, and Co) in small, medium, and large individuals of Mytilus galloprovincialis and Perna perna mussel species along the Algerian coast.

This research paper focused on the monitoring of marine sites using mussels, which are highly valuable organisms in assessing environmental health. However, a significant challenge arises when determining the appropriate size of mussels for monitoring purposes. The objective of this study was to examine the levels of Cd, Pb, As, and Co in three different size classes of two mussel species, Mytilus galloprovincialis and Perna perna, collected from three sites along the Algerian coast, each exhibiting varying degrees of pollution.At each of the study sites, a total of thirty individuals from small, medium, and large size classes of mussels were collected during four different time periods. The mussels were then dissected, and the concentrations of Cd, Pb, As, and Co were measured in the entire flesh of the mussels using ICP-MS.Across the various study sites, the concentrations of cadmium, lead, arsenic, and cobalt ranged from 0.06 to 1.32 mg/kg, 0.09 to 12.56 mg/kg, 4.23 to 18.31 mg/kg, and 0.11 to 1.85 mg/kg, respectively. Interestingly, the distribution of these metals in the three different size classes of mussels followed a consistent pattern at all the study sites. Large mussels exhibited higher concentrations, while small and medium-sized mussels displayed lower levels. These findings highlight substantial spatial and temporal variations in metal concentrations within the studied sites.

The effect of interspecific and intraspecific diversity on microplastic ingestion in two co-occurring mussel species in South Africa.

Interspecific and intraspecific diversity are essential components of biodiversity with far-reaching implications for ecosystem function and service provision. Importantly, genotypic and phenotypic variation within a species can affect responses to anthropogenic pressures more than interspecific diversity. We investigated the effects of interspecific and intraspecific diversity on microplastic ingestion by two coexisting mussel species in South Africa, Mytilus galloprovincialis and Perna perna, the latter occurring as two genetic lineages. We found significantly higher microplastic abundance in M. galloprovincialis (0.54 ± 0.56 MP items g-1WW) than P. perna (0.16 ± 0.21 MP items g-1WW), but no difference between P. perna lineages. Microbeads were the predominant microplastic (76 % in P. perna, 99 % in M. galloprovincialis) and polyethylene the prevalent polymer. Interspecific differences in microplastic abundance varied across locations, suggesting diverse sources of contamination. We suggest that microplastic ingestion can be species-specific even in organisms that coexist and play similar functional roles within ecosystems.

Efficacy of commercial peroxyacetic acid on Vibrio parahaemolyticus planktonic cells and biofilms on stainless steel and Greenshell™ mussel (Perna canaliculus) surfaces.

The potential of using commercial peroxyacetic acid (PAA) for Vibrio parahaemolyticus sanitization was evaluated. Commercial PAA of 0.005 % (v/v, PAA: 2.24 mg/L, hydrogen peroxide: 11.79 mg/L) resulted in a planktonic cell reduction of >7.00 log10 CFU/mL when initial V. parahaemolyticus cells averaged 7.64 log10 CFU/mL. For cells on stainless steel coupons, treatment of 0.02 % PAA (v/v, PAA: 8.96 mg/L, hydrogen peroxide: 47.16 mg/L) achieved >5.00 log10 CFU/cm2 reductions in biofilm cells for eight strains but not for the two strongest biofilm formers. PAA of 0.05 % (v/v, PAA: 22.39 mg/L, hydrogen peroxide: 117.91 mg/L) was required to inactivate >5.00 log10 CFU/cm2 biofilm cells from mussel shell surfaces. The detection of PAA residues after biofilm treatment demonstrated that higher biofilm production resulted in higher PAA residues (p < 0.05), suggesting biofilm is acting as a barrier interfering with PAA diffusing into the matrices. Based on the comparative analysis of genomes, robust biofilm formation and metabolic heterogeneity within niches might have contributed to the variations in PAA resistance of V. parahaemolyticus biofilms.

Plasma ß-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 ß-1,3 glucan binding protein (ß-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 ß-GBP enhanced the phagocytic response of hemocytes. Such ß-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 ß-1,3 glucans), glucose, as well as polyclonal antibodies raised against ß-GBP. These observations clearly indicate that the plasma ß-GBP can possibly recognize and bind to ß-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 ß-GBP in the marine mussel P. viridis.

Sex-specific metabolic dysregulation in digestive glands of green mussels following exposure to triazophos.

As a ubiquitous environmental pollutant in China, triazophos (TP) is known to have neurotoxicity, oxidative stress, and reproductive toxicity to mussels. To investigate the molecular mechanisms of TP toxicity, metabolic changes in the digestive glands of Perna viridis in different sexes were examined after treated with 35 µg/L TP. Notably, 158 significant different metabolites (SDMs) were detected in TP-treated mussels and more than half of the SDMs were lipids and lipid-like molecules, which suggested that TP disturbed the lipid metabolism of P. viridis. In addition, metabolites associated with neurotoxicity and reproductive disturbance were also detected in female and male mussels. Moreover, a larger number of SDMs were found in male mussels (120 SDMs) than females (99 SDMs), and 60 common metabolites exhibited consistent variation tendency and similar magnitude in both sexes. The metabolic alternations in female and male mussels displayed similar protective mechanisms and also sex-specific responses, male mussels were more sensitive to TP exposure. This research provided new data about the molecular mechanisms of TP toxicity and the gender specific changes in mussels after treated by chemicals.

Exposure to Alexandrium spp. impairs the development of Green-lipped mussel (Perna canaliculus) embryos and larvae.

The green-lipped mussel (GLM) Perna canaliculus is an economically, ecologically, and culturally important species in Aotearoa New Zealand. Since 2011, harmful algal blooms (HABs) of Alexandrium spp. have occurred annually in the Marlborough Sounds, the largest GLM aquaculture region in New Zealand. Across a similar timeframe, there has been a severe reduction in wild spat (juvenile mussel) catch. This research investigated the effects of Alexandrium pacificum (which produces paralytic shellfish toxins; PSTs) and A. minutum (a non-producer of PSTs) on the development of four GLM larval life stages (gametes, embryos, D-stage and settlement). Early life stages of GLM were exposed to environmentally relevant concentrations of Alexandrium spp. as whole cell, lysate and filtrate treatments. A 48-h exposure of embryos to whole A. pacificum cells at 500 cells mL-1 caused lysis of embryos, severe abnormalities, and reduced development through to veliger (D-stage) larvae by 85%. GLM growth was impaired at cell concentrations as low as 250 cells mL-1 during a 4-day exposure of D-stage larvae to both Alexandrium spp. Exposure of GLM to both whole and lysed treatments of Alexandrium spp. at 500 cells mL-1 resulted in halved larval growth rates (2.00 µm day-1 vs 4.48 µm day-1 in the control) and growth remained impeded during a 4-day recovery period. Both A. pacificum and A. minutum were found to negatively impact D-larvae. Both whole-cell and lysed-cell treatments of A. pacificum had similar negative effects, suggesting that Alexandrium spp. toxicity to D-larvae is independent of PSTs. Additionally, cell membrane-free treatments of A. pacificum had no negative effects on embryo development, indicating that cell surface-associated bioactive compounds may be responsible for the observed negative effects during this early life stage. Conversely, non-PST-producing A. minutum was toxic to D-stage larvae but not to embryos; larval growth was reduced following a brief 1 h exposure of sperm to cell membrane-free treatments of A. pacificum. No effects were recorded in GLM larvae exposed during settlement, highlighting the potential for differences in susceptibility of early life stages to Alexandrium spp. exposure and the influence of exposure durations. In the wild, blooms of Alexandrium spp. can persist for several months, reaching cell densities higher than those investigated in the present study, and as such may be detrimental to the vulnerable early life stages of GLM.