Functional Analysis of ß-Carotene Oxygenase 2 (BCO2) Gene in Yesso Scallop (Patinopecten yessoensis).

Carotenoids are essential nutrients for humans and animals, and carotenoid coloration represents an important meat quality parameter for many farmed animals. Increasingly, studies have demonstrated that vertebrate carotenoid cleavage oxygenases (CCOs) are essential enzymes in carotenoid metabolism and are therefore potential candidate genes for improving carotenoid deposition. However, our understanding of carotenoid bioavailability and CCOs functions in invertebrates, particularly marine species, is currently quite limited. We previously identified that a CCO homolog, PyBCO-like 1, was the causal gene for carotenoid coloration in the 'Haida golden scallop', a variety of Yesso scallop (Patinopecten yessoensis) characterized by carotenoid enrichment. Here, we found that another CCO-encoding gene named PyBCO2 (ß-carotene oxygenase 2) was widely expressed in P. yessoensis organs/tissues, with the highest expression in striated muscle. Inhibiting BCO2 expression in P. yessoensis through RNA interference led to increased carotenoid (pectenolone and pectenoxanthin) deposition in the striated muscle, and the color of the striated muscle changed from white to light orange. Our results indicate that PyBCO2 might be a candidate gene used for improving carotenoid content in normal Yesso scallops, and also in 'Haida golden scallops'.

Integrated ultra-high pressure and salt addition to improve the in vitro digestibility of myofibrillar proteins from scallop mantle (Patinopecten yessoensis).

Myofibrillar protein (MP) is susceptible to the effect of ionic strength and ultra-high pressure (UHP) treatment, respectively. However, the impact of UHP combined with ionic strength on the structure and in vitro digestibility of MP from scallop mantle (Patinopecten yessoensis) is not yet clear. Therefore, it is particularly important to analyze the structural properties and enhance the in vitro digestibility of MP by NaCl and UHP treatment. The findings demonstrated that as ionic strength increased, the α-helix and ß-sheet gradually transformed into ß-turn and random coil. The decrease of endogenous fluorescence intensity indicated the formation of a more stable tertiary structure. Additionally, the exposure of internal sulfhydryl groups increased the amount of total sulfhydryl content, and reactive sulfhydryl groups gradually transformed into disulfide bonds. Moreover, it reduces aggregation through increased solubility, decreased turbidity, particle sizes, and a relatively dense and uniform microstructure. When MP from the scallop mantle was treated with 0.5 mol/L ionic strength and 200 MPa UHP treatment, it had the highest solubility (90.75 ± 0.13%) and the lowest turbidity (0.41 ± 0.03). The scallop mantle MP with NaCl of 0.3 mol/L and UHP treatment had optimal in vitro digestibility (95.14 ± 2.01%). The findings may offer a fresh perspectives for developing functional foods for patients with dyspepsia and a theoretical foundation for the comprehensive utilization of scallop mantle by-products with low concentrations of NaCl.

Scallop-bacteria symbiosis from the deep sea reveals strong genomic coupling in the absence of cellular integration.

Previous studies have revealed tight metabolic complementarity between bivalves and their endosymbiotic chemosynthetic bacteria, but little is known about their interactions with ectosymbionts. Our analysis of the ectosymbiosis between a deep-sea scallop (Catillopecten margaritatus) and a gammaproteobacterium showed that bivalves could be highly interdependent with their ectosymbionts as well. Our microscopic observation revealed abundant sulfur-oxidizing bacteria (SOB) on the surfaces of the gill epithelial cells. Microbial 16S rRNA gene amplicon sequencing of the gill tissues showed the dominance of the SOB. An analysis of the SOB genome showed that it is substantially smaller than its free-living relatives and has lost cellular components required for free-living. Genomic and transcriptomic analyses showed that this ectosymbiont relies on rhodanese-like proteins and SOX multienzyme complex for energy generation, mainly on the Calvin-Benson-Bassham (CBB) cycle and peripherally on a phosphoenolpyruvate carboxylase for carbon assimilation. Besides, the symbiont encodes an incomplete tricarboxylic acid (TCA) cycle. Observation of the scallop's digestive gland and its nitrogen metabolism pathways indicates it does not fully rely on the ectosymbiont for nutrition. Analysis of the host's gene expression provided evidence that it could offer intermediates for the ectosymbiont to complete its TCA cycle and some amino acid synthesis pathways using exosomes, and its phagosomes, endosomes, and lysosomes might be involved in harvesting nutrients from the symbionts. Overall, our study prompts us to rethink the intimacy between the hosts and ectosymbionts in Bivalvia and the evolution of chemosymbiosis in general.

Potential roles of hydroxybenzoate paralytic shellfish toxins in modulating toxin biokinetics in scallops.

Paralytic shellfish toxins (PSTs) produced by some marine dinoflagellates can cause severe human intoxication via vectors like bivalves. Toxic dinoflagellate Gymnodinium catenatum produce a novel group of hydroxybenzoate PSTs named GC toxins, but their biokinetics in bivalves haven't been well examined. In this experiment, we analyzed PSTs in bay scallops Argopecten irradians exposed to G. catenatum (strain MEL11) to determine their accumulation, elimination, anatomical distribution, and biotransformation. To our surprise, up to 30% of the PSTs were accumulated in the adductor muscle of scallops at the end of the experiment, and the toxicity of adductor muscle exceeded the regulatory limit of 800 µg STXeq/kg in only 6 days. High concentration of toxins in the adductor muscle are likely linked to the rapid transfer of GC toxins from viscera to other tissues. Moreover, most GC toxins in scallops were found rapidly transformed to decarbamoyl toxins through enzyme-mediated hydrolysis, which was further supported by the in vitro incubation experiments. Our study demonstrates that GC toxins actively participate in toxin distribution and transformation in scallops, which may increase the risks of food poisoning associated with the consumption of scallop adductor muscle. ENVIRONMENTAL IMPLICATION: The negative impacts of harmful algal blooms (HABs) have become a global environmental concern under the joint effects of cultural eutrophication and climate change. Our study, targeted on the biokinetics of paralytic shellfish toxins in scallops exposed to Gymnodinium catenatum producing unique GC toxins, aims to elucidate potential risks of seafood poisoning associated with GC toxins. The findings of this study will help us to understand the roles of GC toxins in seafood poisoning, and to develop effective management strategies against toxic algal blooms and phycotoxins.

The amnesic shellfish poisoning toxin, domoic acid: The tattoo of the king scallop Pecten maximus.

Domoic acid (DA) is a potent neurotoxin produced by diatoms of the genus Pseudo-nitzschia and is responsible for Amnesic Shellfish Poisoning (ASP) in humans. Some fishery resources of high commercial value, such as the king scallop Pecten maximus, are frequently exposed to toxic Pseudo-nitzschia blooms and are capable of accumulating high amounts of DA, retaining it for months or even a few years. This poses a serious threat to public health and a continuous economical risk due to fishing closures of this resource in the affected areas. Recently, it was hypothesized that trapping of DA within autophagosomic-vesicles could be one reason explaining the long retention of the remaining toxin in P. maximus digestive gland. To test this idea, we follow the kinetics of the subcellular localization of DA in the digestive glands of P. maximus during (a) the contamination process - with sequential samplings of scallops reared in the field during 234 days and naturally exposed to blooms of DA-producing Pseudo-nitzschia australis, and (b) the decontamination process - where highly contaminated scallops were collected after a natural bloom of toxic P. australis and subjected to DA-depuration in the laboratory for 60 days. In the digestive gland, DA-depuration rate (0.001 day-1) was much slower than contamination kinetics. The subcellular analyses revealed a direct implication of early autophagy in DA sequestration throughout contamination (r = 0.8, P < 0.05), while the presence of DA-labeled residual bodies (late autophagy) appeared to be strongly and significantly related to slow DA-depuration (r = -0.5) resembling an analogous DA-tattooing in the digestive glands of P. maximus. This work provides new evidence about the potential physiological mechanisms involved in the long retention of DA in P. maximus and represents the baseline to explore procedures to accelerate decontamination in this species.

Hybrid surgery of vertebral artery transposition combined with scallop and fenestration technique for the repair of type B aortic dissection patient with isolated left vertebral artery: A case report.

RATIONALE: Acute type B aortic dissection (ABAD) is a fatal cardiovascular disease with high morbidity and mortality. Isolated left vertebral artery (ILVA) is a rare aortic arch mutation originating from the aortic arch. The simultaneous occurrence of both increases the complexity and difficulty of thoracic endovascular aortic repair. However, there have been few reports on the recommendation of thoracic endovascular aortic repair treatment strategies for aortic dissection patients concomitant ILVA with insufficient landing zone. Here, we report a case of ABAD combined with ILVA treated with hybrid surgery of left vertebral artery transposition alliance with Scallop and in vivo fenestration endograft. PATIENT CONCERNS: A 38-year-old middle-aged man was transferred to our vascular department with persistent pain in his lower abdomen for 8 hours. DIAGNOSES: Preoperative computed tomography angiogram of the thoracic and abdominal aorta diagnosed with ABAD accompanied with ILVA. INTERVENTIONS: Hybrid surgery of left vertebral artery transposition alliance with Scallop and in situ fenestration endograft for revascularization of ILVA, left subclavian artery, and left common carotid artery. OUTCOMES: The hybridization operation was successfully completed. There were no complications of cerebral and spinal cord ischemia after operation. Computed tomography angiogram examination indicated no internal leakage existed in the stent and patency of the arch vessels and the transposed left vertebral artery follow-up 3 months after surgery. LESSONS: This study gave us experience in the treatment of aortic dissection with left vertebral artery variation and suggested that left vertebral artery transposition combined with scallop and in vivo fenestration stent is safe and effective.

Water stratification alters phytoplankton assemblages in scallop farming waters of the North Yellow Sea in China.

As evaluation indicators of the primary productivity, the phytoplankton biomass and community structure are of great significance to the fishery industry, which can be driven by ocean currents, nutrients and water stratification. In the present study, the characteristics of phytoplankton assemblages in different water layers of a typical Yesso scallop farming area in Zhangzi Island, the North Yellow Sea were investigated from March 2021 to January 2022. According to the vertical distribution of temperature, water stratification was observed from June to August (stratification period), and disappeared in March, October and the following January with vertical homogeneity (mixing period). 18S rRNA gene sequencing results revealed that Pyrrophyta was the most dominant phylum during the sampling period, with high gene proportions in the stratification (63.36%) and mixing periods (77.35%). The gene proportion of Bacillariophyta in the stratification period was 5.44%, which was significantly lower than that in the mixing period of 8.93% (p < 0.05). Moreover, Pseudo-nitzschia, a toxin-producing taxon affiliated with Bacillariophyta, exhibited a significantly higher proportion in the stratification period than in the mixing period. During the stratification period, a number of toxin-producing taxa such as Pseudo-nitzschia and Karlodinium were enriched in the bottom layer, which was 1.29-fold and 1.37-fold of that in the surface layer, respectively. Redundancy analysis showed that phosphate and water temperature were major environmental factors driving the vertical distribution of phytoplankton assemblages. The phosphate (0.11 µM) and silicate (2.09 µM) concentrations in the surface layer approached the minimum threshold for phytoplankton growth, and the stoichiometric limitation of phosphate was detected in the surface and middle layers. Collectively, these results indicated that the decreased proportion ratio of Bacillariophyta to Pyrrophyta and unfavorable community composition of Bacillariophyta for scallops were observed during summer, which might result from the phosphate limitation driven by water stratification. The results will further our understanding of the dynamics of phytoplankton communities under the background of intensifying ocean stratification and provide ecological guidance for mollusc mariculture.

Paralytic shellfish toxins producing dinoflagellates cause dysbacteriosis in scallop gut microbial biofilms.

Filter-feeding bivalves could accumulate paralytic shellfish toxins (PSTs) produced by harmful dinoflagellates through diet. Despite that bivalves are resistant to these neurotoxins due to possessing PST-resistant sodium channel, exposure to PSTs-producing dinoflagellates impair bivalve survival. We hypothesized that ingesting PSTs-producing dinoflagellates may influence the gut microbiota, and then the health of bivalves. To test this idea, we compared the gut microbiota of the scallop Patinopecten yessoensis, after feeding with PST-producing or non-toxic dinoflagellates. Exposure to PSTs-producing dinoflagellates resulted in a decline of gut microbial diversity and a disturbance of community structure, accompanied by a significant increase in the abundance and richness of pathogenic bacteria, represented by Vibrio. Moreover, network analysis demonstrated extensive positive correlations between pathogenic bacteria abundances and PSTs concentrations in the digestive glands of the scallops. Furthermore, isolation of a dominant Vibrio strain and its genomic analysis revealed a variety of virulence factors, including the tolC outer membrane exporter, which were expressed in the gut microbiota. Finally, the infection experiment demonstrated scallop mortality caused by the isolated Vibrio strain; further, the pathogenicity of this Vibrio strain was attenuated by a mutation in the tolC gene. Together, these findings demonstrated that the PSTs may affect gut microbiota via direct and taxa-specific interactions with opportunistic pathogens, which proliferate after transition from seawater to the gut environment. The present study has revealed novel mechanisms towards deciphering the puzzles in environmental disturbances-caused death of an important aquaculture species.

The physiological response of the clam Ruditapes philippinarum and scallop Chlamys farreri to varied concentrations of microplastics exposure.

Microplastics (MPs) pollution's impact on the marine ecosystem is widely recognized. This study compared the effects of polyethylene (PE) and polyethylene terephthalate (PET) on two bivalve species, Ruditapes philippinarum (clam) and Chlamys farreri (scallop), at two particle concentrations (10 and 1000 µg/L). MPs were found in the digestive glands and gills of both species. Although clearance rates showed no significant changes, exposure to different MPs caused oxidative stress, energy disruption, and lipid metabolism disorders in both clam and scallop. Histopathological damage was observed in gills and digestive glands. IBR values indicated increasing toxicity with concentration, with PET being more toxic than PE. WOE model suggested increasing hazard with concentration, highlighting higher PET toxicity on clam digestive glands. In contrast, PE hazard increased in gills, showing different species responses. R. philippinarum exhibited higher sensitivity to MPs than C. farreri, providing insights for assessing ecological risk under realistic conditions and stress conditions.

Functional analyses of TRAF6 gene in Argopecten scallops.

The tumor necrosis factor (TNF) receptor-associated factor (TRAF) family has been reported to be involved in many immune pathways. In a previous study, we identified 5 TRAF genes, including TRAF2, 3, 4, 6, and 7, in the bay scallop (Argopecten irradians, Air) and the Peruvian scallop (Argopecten purpuratus, Apu). Since TRAF6 is a key molecular link in the TNF superfamily, we conducted a series of studies targeting the TRAF6 gene in the Air and Apu scallops as well as their hybrid progeny, Aip (Air ♀ × Apu ♂) and Api (Apu ♀ × Air ♂). Subcellular localization assay showed that the Air-, Aip-, and Api-TRAF6 were widely distributed in the cytoplasm of the human embryonic kidney cell line (HEK293T). Additionally, dual-luciferase reporter assay revealed that among TRAF3, TRAF4, and TRAF6, only the overexpression of TRAF6 significantly activated NF-κB activity in the HEK293T cells in a dose-dependent manner. These results suggest a crucial role of TRAF6 in the immune response in Argopecten scallops. To investigate the specific immune mechanism of TRAF6 in Argopecten scallops, we conducted TRAF6 knockdown using RNA interference. Transcriptomic analyses of the TRAF6 RNAi and control groups identified 1194, 2403, and 1099 differentially expressed genes (DEGs) in the Air, Aip, and Api scallops, respectively. KEGG enrichment analyses revealed that these DEGs were primarily enriched in transport and catabolism, amino acid metabolism, peroxisome, lysosome, and phagosome pathways. Expression profiles of 28 key DEGs were confirmed by qRT-PCR assays. The results of this study may provide insights into the immune mechanisms of TRAF in Argopecten scallops and ultimately benefit scallop breeding.

Effect of acute cadmium exposure on oxidative stress and antioxidant system of the scallop Aequipecten tehuelchus.

This study aimed to assess the impact of acute exposure (96 h) to Cd in gills, digestive gland and muscle of the Tehuelche scallop Aequipecten tehuelchus from San José gulf in Patagonia, Argentina. Scallops were exposed to Cd concentrations of 0, 25, 50, 100, 150, 204, 275, 371, and 500 µg/L, and mortality rates were recorded after 96 h of exposure. Surviving organisms were analyzed for the biochemical response through reactive oxygen and nitrogen species (RONS), activities of catalase (CAT) and glutathione-S-transferase (GST), metallothioneins (MT), lipid peroxidation (LPO) and liposoluble antioxidants α-tocopherol (α-T) and ß-carotene (ß-C). The mean lethal concentration (LC50) was 155.8 µg Cd/L, a lower value than other scallops' species, showing that A. tehuelchus has a particular sensitivity to Cd. In the three tissues, at all exposure concentrations, there was no significant response in RONS levels, GST activity or LPO. Nevertheless, CAT activity and α-T levels decreased in the gills but increased in the digestive gland, with no significant response in the muscle. Two-way ANOVA revealed a significant interaction between Cd concentration and tissue on MT, which increased significantly in gills, decreased in digestive gland with 100 compared to 50 µg Cd/L; whereas in muscle a significant increase was observed with 25 µg Cd/L compared to control. The results show a significant effect of Cd in scallop's gills on CAT activity and α-T levels, highlighting this tissue as the primary target against relevant concentrations of metal in seawater. The effect on digestive gland and muscle was minimal. The overall results suggest that Cd toxicity is tissue-specific. This study will help reduce the existence knowledge gap regarding potential impacts of acute exposure to Cd in a bivalve species with high ecological and commercial importance, as well as identifying the most responsive biomarkers associated with Cd stress for monitoring assessment.

Effects of the toxic dinoflagellate Protoceratium reticulatum and its yessotoxins on the survival and feed ingestion of Argopecten purpuratus veliger larvae.

The effects of yessotoxins (YTXs) produced by the dinoflagellate Protoceratium reticulatum in the early stages of bivalves have not been studied in detail. The present study evaluates the effects of P. reticulatum and YTXs on the survival and feed ingestion of veliger larvae of Argopecten purpuratus. Larvae were 96 h-exposed to 500, 1000 and 2000 P. reticulatum cells mL-1, and their equivalent YTX extract was prepared in methanol. Results show a survival mean of 82 % at the highest density of dinoflagellate, and 38 % for larvae with the highest amount of YTX extract. Feed ingestion is reduced in the dinoflagellate exposure treatments as a function of cell density. Therefore, the effect of YTXs on A. purpuratus represents a new and important area of study for investigations into the deleterious effects of these toxins in the early stages of the life cycle of this and, potentially, other bivalves.

Genome-wide investigation of the TGF-ß superfamily in scallops.

BACKGROUND: Transforming growth factor ß (TGF-ß) superfamily genes can regulate various processes, especially in embryogenesis, adult development, and homeostasis. To understand the evolution and divergence patterns of the TGF-ß superfamily in scallops, genome-wide data from the Bay scallop (Argopecten irradians), the Zhikong scallop (Chlamys farreri) and the Yesso scallop (Mizuhopecten yessoensis) were systematically analysed using bioinformatics methods. RESULTS: Twelve members of the TGF-ß superfamily were identified for each scallop. The phylogenetic tree showed that these genes were grouped into 11 clusters, including BMPs, ADMP, NODAL, GDF, activin/inhibin and AMH. The number of exons and the conserved motif showed some differences between different clusters, while genes in the same cluster exhibited high similarity. Selective pressure analysis revealed that the TGF-ß superfamily in scallops was evolutionarily conserved. The spatiotemporal expression profiles suggested that different TGF-ß members have distinct functions. Several BMP-like and NODAL-like genes were highly expressed in early developmental stages, patterning the embryonic body plan. GDF8/11-like genes showed high expression in striated muscle and smooth muscle, suggesting that these genes may play a critical role in regulating muscle growth. Further analysis revealed a possible duplication of AMH, which played a key role in gonadal growth/maturation in scallops. In addition, this study found that several genes were involved in heat and hypoxia stress in scallops, providing new insights into the function of the TGF-ß superfamily. CONCLUSION: Characteristics of the TGF-ß superfamily in scallops were identified, including sequence structure, phylogenetic relationships, and selection pressure. The expression profiles of these genes in different tissues, at different developmental stages and under different stresses were investigated. Generally, the current study lays a foundation for further study of their pleiotropic biological functions in scallops.

PyLKB1 regulates glucose transport via activating PyAMPKα in Yesso Scallop Patinopecten yessoensis under high temperature stress.

Liver kinase B1 (LKB1) is a classical serine/threonine protein kinase and plays an important role in maintaining energy homeostasis through phosphorylate AMP-activated protein kinase α subunit (AMPKα). In this study, a homologous molecule of LKB1 with a typical serine/threonine kinase domain and two nuclear localization sequences (NLSs) was identified in Yesso Scallop Patinopecten yessoensis (PyLKB1). The mRNA transcripts of PyLKB1 were found to be expressed in haemocytes and all the examined tissues, including gill, mantle, gonad, adductor muscle and hepatopancreas, with the highest expression level in hepatopancreas. PyLKB1 was mainly located in cytoplasm and nucleus of scallop haemocytes. At 3 h after high temperature stress treatment (25 °C), the mRNA transcripts of PyLKB1, PyAMPKα, and PyGLUT1 in hepatopancreas, the phosphorylation level of PyAMPKα at Thr170 in hepatopancreas, the positive fluorescence signals of PyLKB1 in haemocytes, glucose analogue 2-NBDG content in haemocytes, and glucose content in hepatopancreas, haemocytes and serum all increased significantly (p < 0.05) compared to blank group (15 °C). However, there was no significant difference at the protein level of PyLKB1 and PyAMPKα. After PyLKB1 was knockdown by siRNA, the mRNA expression level of PyGLUT1, and the glucose content in hepatopancreas and serum were significantly down-regulated (p < 0.05) compared with the negative control group receiving an injection of siRNA-NC. However, there were no significant difference in PyGLUT1 expression, glucose content and glucose analogue 2-NBDG content in haemocytes. These results collectively suggested that PyLKB1-PyAMPKα pathway was activated to promote glucose transport by regulating PyGLUT1 in response to high temperature stress. These results would be helpful for understanding the function of PyLKB1-PyAMPKα pathway in regulating glucose metabolism and maintaining energy homeostasis under high temperature stress in scallops.

Interactive effects of multiple antibiotic residues and ocean acidification on physiology and metabolome of the bay scallops Argopecten irradians irradians.

Coastal areas are confronted with compounding threats arising from both climatic and non-climatic stressors. Antibiotic pollution and ocean acidification are two prevalently concurrent environmental stressors. Yet their interactive effects on marine biota have not been investigated adequately and the compound hazard remain obscure. In this study, bay scallops Argopecten irradians irradians were exposed to multiple antibiotics (sulfamethoxazole, tetracycline, oxytetracycline, norfloxacin, and erythromycin, each at a concentration of 1 µg/L) combined with/without acidic seawater (pH 7.6) for 35 days. The single and interactive effects of the two stressors on A. irradians irradians were determined from multidimensional bio-responses, including energetic physiological traits as well as the molecular underpinning (metabolome and expressions of key genes). Results showed that multiple antibiotics predominantly enhanced the process of DNA repair and replication via disturbing the purine metabolism pathway. This alternation is perhaps to cope with the DNA damage induced by oxidative stress. Ocean acidification mainly disrupted energy metabolism and ammonia metabolism of the scallops, as evidenced by the increased ammonia excretion rate, the decreased O:N ratio, and perturbations in amino acid metabolism pathways. Moreover, the antagonistic effects of multiple antibiotics and ocean acidification caused alternations in the relative abundance of neurotransmitter and gene expression of neurotransmitter receptors, which may lead to neurological disorders in scallops. Overall, the revealed alternations in physiological traits, metabolites and gene expressions provide insightful information for the health status of bivalves in a natural environmental condition under the climate change scenarios.

A molluscan IRF interacts with IKKα/ß family protein and modulates NF-κB and MAPK activity.

Interferon regulatory factor (IRF) family proteins are key transcription factors involved in vital physiological processes such as immune defense. However, the function of IRF in invertebrates, especially in marine shellfish is not clear. In this study, a new IRF gene (CfIRF2) was identified in the Zhikong scallop, Chlamys farreri, and its immune function was analyzed. CfIRF2 has an open reading frame of 1107 bp encoding 368 amino acids. The N-terminus of CfIRF2 consists of a typical IRF domain, with conserved amino acid sequences. Phylogenetic analysis suggested close evolutionary relationship with shellfish IRF1 subfamily proteins. Expression pattern analysis showed that CfIRF2 mRNA was expressed in all tissues, with the highest expression in the hepatopancreas and gills. CfIRF2 gene expression was substantially enhanced by a pathogenic virus (such as acute viral necrosis virus) and poly(I:C) challenge. Co-immunoprecipitation assay identified CfIRF2 interaction with the IKKα/ß family protein CfIKK1 of C. farreri, demonstrating a unique signal transduction mechanism in marine mollusks. Moreover, CfIRF2 interacted with itself to form homologous dimers. Overexpression of CfIRF2 in HEK293T cells activated reporter genes containing interferon stimulated response elements and NF-κB genes in a dose-dependent manner and promoted the phosphorylation of protein kinases (JNK, Erk1/2, and P38). Our results provide insights into the functions of IRF in mollusks innate immunity and also provide valuable information for enriching comparative immunological theory for the prevention of diseases in scallop farming.

Tissue-specific antioxidative response and metabolism of paralytic shellfish toxins in scallop (Chlamys farreri) mantle with Alexandrium dinoflagellate exposure.

Bivalves show remarkable capacity to acclimate paralytic shellfish toxins (PSTs) produced by dinoflagellates, severely affecting fishery industry and public health. Here, transcriptomic response to PSTs-producing dinoflagellate (Alexandrium minutum) was investigated in Zhikong scallop (Chlamys farreri) mantle. The PSTs accumulated in C. farreri mantle continually increased during the 15 days exposure, with "oxidation-reduction" genes induced compared to the control group at the 1st and 15th day. Through gene co-expression network analysis, 16 PSTs-responsive modules were enriched with up- or down-regulated genes. The concentration of GTXs, major PSTs in A. minutum and accumulated in scallops, was correlated with the up-regulated magenta module, enriching peroxisome genes as the potential mantle-specific PSTs biomarker. Moreover, Hsp70B2s were inhibited throughout the exposure, which together with the expanded neurotransmitter transporter SLC6As, may play essential roles on neurotransmitter homeostasis in scallop mantle. These results paved the way for a comprehensive understanding of defensive mechanism and homeostatic response in scallop mantle against PSTs.

The assessment of bioavailability and environmental risk of dissolved and particulate polycyclic aromatic hydrocarbons in the seawater of typical bays.

The pollution of dissolved and particulate polycyclic aromatic hydrocarbons (PAHs) in coastal waters has been increasing in recent decades. However, limited research has been conducted on the characteristics of dissolved and particulate PAHs in seawater and their associated risk assessment. Here, we focused on the bioavailability and environmental risk of PAHs in four typical bays of Shandong Province, China, and used scallop Chlamys farreri and clam Mactra veneriformis as sentinel species. The results revealed that dissolved PAHs tended to bioaccumulate in scallop C. farreri, and their ecological risk exhibited a significant correlation with the health risk of bioaccumulated PAHs and the bioeffect of screened biomarkers in scallop. Conversely, particulate PAHs demonstrated a higher bioaccumulation potential in the clam M. veneriformis, showing a stronger correlation between their ecological risk, health risk, and bioeffect in clams. This study provides the first elucidation of the connection between the ecological risk, health risk, and bioeffect of PAHs. Furthermore, based on the better correlation of health risk and bioeffect caused by PAHs with total PAHs in seawater, we propose that the clam M. veneriformis is a more suitable sentinel species for assessing environmental risk in typical bays of Shandong Province.

Intrinsic and extrinsic pathways of apoptosis induced by multiple antibiotics residues and ocean acidification in hemocytes of scallop Argopecten irradians irradians: An interactionist perspective.

The increasing prevalence of antibiotics in seawater across global coastal areas, coupled with the ocean acidification induced by climate change, present a multifaceted challenge to marine ecosystems, particularly impacting the key physiological processes of marine organisms. Apoptosis is a critical adaptive response essential for maintaining cellular homeostasis and defending against environmental threats. In this study, bay scallops Argopecten irradians irradians were exposed to multiple antibiotics (sulfamethoxazole, tetracycline, oxytetracycline, norfloxacin, and erythromycin, each at a concentration of 1 µg/L) combined with/without acidic seawater (pH 7.6) for 35 days. The single and interactive effects of the two stressors on apoptosis and the underlying mechanisms in hemocytes of A. irradians irradians were determined through flow cytometry analysis, comet assay, oxidative stress biomarkers analysis, and transcriptome analysis. Results showed that apoptosis could be triggered by either AM exposure or OA exposure, but through different pathways. Exposure to AM leads to mitochondrial dysfunction and oxidative damage, which in turn triggers apoptosis via a series of cellular events in both intrinsic and extrinsic pathways. Conversely, while OA exposure similarly induced apoptosis, its effects are comparatively subdued and are predominantly mediated through the intrinsic pathway. Additionally, the synergistic effects of AM and OA exposure induced pronounced mitochondrial dysfunction and oxidative damages in the hemocytes of A. irradians irradians. Despite the evident cellular distress and the potential initiation of apoptotic pathways, the actual execution of apoptosis appears to be restrained, which might be attributed to an energy deficit within the hemocytes. Our findings underscore the constrained tolerance capacity of A. irradians irradians when faced with multiple environmental stressors, and shed light on the ecotoxicity of antibiotic pollution in the ocean under prospective climate change scenarios.

Comparative study of domoic acid accumulation, isomer content and associated digestive subcellular processes in five marine invertebrate species.

Despite the deleterious effects of the phycotoxin domoic acid (DA) on human health, and the permanent threat of blooms of the toxic Pseudo-nitzschia sp. over commercially important fishery-resources, knowledge regarding the physiological mechanisms behind the profound differences in accumulation and depuration of this toxin in contaminated invertebrates remain very scarce. In this work, a comparative analysis of accumulation, isomer content, and subcellular localization of DA in different invertebrate species was performed. Samples of scallops Pecten maximus and Aequipecten opercularis, clams Donax trunculus, slippersnails Crepidula fornicata, and seasquirts Asterocarpa sp. were collected after blooms of the same concentration of toxic Pseudo-nitzschia australis. Differences (P < 0.05) in DA accumulation were found, wherein P. maximus showed up to 20-fold more DA in the digestive gland than the other species. Similar profiles of DA isomers were found between P. maximus and A. opercularis, whereas C. fornicata was the species with the highest biotransformation rate (∼10 %) and D. trunculus the lowest (∼4 %). DA localization by immunohistochemical analysis revealed differences (P < 0.05) between species: in P. maximus, DA was detected mainly within autophagosome-like vesicles in the cytoplasm of digestive cells, while in A. opercularis and C. fornicata significant DA immunoreactivity was found in post-autophagy residual bodies. A slight DA staining was found free within the cytoplasm of the digestive cells of D. trunculus and Asterocarpa sp. The Principal Component Analysis revealed similarities between pectinids, and a clear distinction of the rest of the species based on their capabilities to accumulate, biotransform, and distribute the toxin within their tissues. These findings contribute to improve the understanding of the inter-specific differences concerning the contamination-decontamination kinetics and the fate of DA in invertebrate species.