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Different sources of proteins have various ways for facilitating the gelation process of surimi matrices, leading to the diverse combined effects with transglutaminase (TG). In this study, the effects of two plant proteins, soy protein isolate (SPI) and pea protein isolate (PPI), and two animal non-muscle proteins, egg white protein (EWP) and whey protein isolate (WPI), with TG addition on the gel properties of clam Meretrix meretrix (MM) surimi gels were investigated, and the mechanisms were explored. In the presence of TG, the exogenous protein addition significantly improved (p < 0.05) the gelation process of the MM surimi. The best improvements were obtained with the combination of EWP, where the gel strength, cooking loss, and water holding capacity were enhanced by 113.08%, 67.89%, and 26.30%, respectively. The addition of SPI showed a relatively weak enhancement compared to EWP incorporation, followed by the addition of PPI and WPI. The results of optical microscopy, differential scanning calorimetry, and chemical forces demonstrated that TG preferentially promoted plant proteins to form self-aggregation in the surimi system, and SPI generated more polymers than PPI. In contrast, the interpenetration of animal proteins and MM myofibrillar proteins was improved by TG. EWP formed a double cross-linking network within the MM protein network, while WPI acted as a binder to promote protein-protein interactions. This research could provide novel insights for developing MM resources and establish a theoretical foundation for the use of composite exogenous protein additives to enhance the gel properties of MM surimi products. • Plant/animal proteins could improve the gelation of TG-added MM surimi. • TG generated more polymers between plant proteins within MM gel network. • SPI generated more self-aggregates than PPI in the presence of TG. • The interpenetration of animal proteins with MM surimi was promoted by TG. • TG induced a double cross-linking network between EWP and MM protein. [ABSTRACT FROM AUTHOR]

Meretrix meretrix were collected for 3 times from 2011 to 2012, at 5 stations along west coast of Guangxi and wild and used as a biological indicator for assessing the marine environmental stress. Six biomarkers at individual, cellular and molecular levels were selected, including time required to drill the sand, phagocytic ability, stability of lysosomal membrane, ferric reducing ability of plasma (FRAP), acetylcholinesterase activity (AChE), and comet rate. Utilizing the Integrated Biological Response Index (IBR) model, the above biomarkers were integratedly analyzed and the data were displayed by intuitionistic star plots to evaluate the environmental situation of the 5 stations. The results indicated that the biological response indices (IBR/ n) of the 5 stations varied between 2.30 and 8.68. Maowei Sea had the highest environmental stress, whereas Beilun Estuary had the lowest. Although different biomarkers were different in response to pollution stress, IBR model could effectively distinguish environmental stress of a specific area. The results of biomarker monitoring were basically in agreement with those of chemical monitoring. [ABSTRACT FROM AUTHOR]

A total of 2,970 EST--SSRs (2.38%) were identified by transcriptome sequencing of clam Meretrix meretrix (751,970 reads, ~310.82 Mbp), using 454 Genome Sequencer FLX next-generation sequencing platform. Dinucleotide SSR was the dominant repeat type (40.2%), followed by trinucleotide (37.8%), tetranuleotide (12.0%) and pentanucleotide (2.0%) SSR. The dominant repeat motif was AT (71.3%) in the dinucleotide SSR type and AAC (45.6%) in the trinucleotide SSR type. Nearly 79% of all microsatellites had flanking sequences suitable for PCR primer design. Half of PAL were found to be polymorphic in a subset of 40 primer pairs randomly selected. Specifically, the density of dinucleotide, trinucleotide and tetranucleotide repeats showed significant variation among four development stages (trochophore, D-veliger, pediveliger and postlarva). The results suggested that dinucleotide, trinucleotide and tetranucleotide SSRs may play an important role in contributing to the different expression profiles in larval stages. [ABSTRACT FROM AUTHOR]

A quinquennial seasonal study (2015–2019) has been conducted to evaluate the bioaccumulation pattern of trace metals in Meretrix meretrix. The concentration of trace metals in the clam was observed as Cr > Cu > Ni > Zn > Pb > Cd > Hg, (Body> Mantle > Gills), similar to sediments. Contamination Factor of Cu and Cr in sediments showed strong association with the corresponding metal concentration in the body (r = 0.687, r = 0.962), mantle (r = 0.880, r = 0.956) and gills (r = 0.937, r = 0.863). Bioconcentration Factor was high for Cr followed by Ni. Mean Metal Concentration Rate (MMCR) of Cr was high and Hg was low (Body>Mantle>Gills). Our study establishes that the trace metal intake by Meretrix meretrix is associated with seasonal variation, physicochemical factors, sediment texture, chemical speciation and the metabolic stress created within the species induced from increased demand for protein synthesis. The latter resulted in the augmented rate of accumulation of Cu and Cr. [Display omitted] • Sediment contamination influenced the bioaccumulation of Cu, Cr, Ni and Zn in Meretrix meretrix & sandy clay sediment functioned as an immediate source for bioavailability of metals. • Visualization of Contamination Factor of sediments with trace metal concentration in body, mantle and gills was achieved by Neural Network Model. • M.M.C.R. is a useful method for calculating the degree of trace metal accumulation per day in sediments and benthic organisms, particularly for long term bioaccumulation studies. • Wet seasons, acidic pH, low salinity & low water temperature favoured metal-specific bioaccumulation in Meretrix meretrix. • Metabolic stress created within the species accelerates feeding activity which in turn intensify the rate of uptake of Cu and Cr. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) has been widely used in industry and can accumulate in the water, soil, and food. Meretrix meretrix is one of the marine shellfishes cultivated for economic purpose in China. The increasing Cd levels in coastal marine water could adversely affect the economic benefits of shellfish cultivation. In the present study, M. meretrix were exposed to different Cd2+ concentrations (0, 1.5, 3, 6, and 12 mg L-1) for 5 d to evaluate the effects of Cd on spermatogenic cell. The Cd accumulation, survival rate and the indices of oxidative stress and apoptosis were determined in the spermatogenic cells of M. meretrix. The expression levels of p53 and metallothionein (MT) mRNA were also measured in the spermatogenic cells. Cd accumulation and the mortality rate of spermatogenic cells were found to increase in a dose-response manner with Cd2+ concentrations. Histopathology changes, especially the damage of membranous structure, were more severe as the Cd2+ levels in the testis became higher. The indexes of oxidative stress, including reactive oxygen species, malondialdehyde, protein carbonyl derivates and DNA-protein crosslinks all increased after exposure to Cd2+. However, the total antioxidant capacity gradually decreased with the increasing Cd2+ concentration. In addition, exposure to Cd2+ increased the apoptotic rate and caspase-3 and 9 activities but decreased the level of mitochondrial membrane potential and cytochrome C oxidase in the spermatogenic cells. MT mRNA expression increased in lower Cd2+ concentration treated groups whereas decreased in higher groups, while the p53 mRNA expression increased in a dose-response manner with Cd2+ and was positively correlated with the oxidative damage indices. These results indicated that Cd2+ caused oxidative stress and p53 induced apoptosis in the spermatogenic cells, and thus decreased the survival rate of sperm cells. This finding highlights that Cd can reduce the reproductive capacity of M. meretrix , thus threatening to wild shellfish populations and reducing the efficiency of shellfish farming. • Exposure to Cd increased mortality rate of spermatogenic cells in Meretrix meretrix. • Exposure to Cd induced oxidative stress and apoptosis in the spermatogenic cells. • Exposure to 3 mg L−1 Cd increased the MT mRNA level while 12 mg L−1 Cd decreased it. • The expression level of p53 mRNA was correlated with the oxidative stress indices. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are well-known persistent organic pollutants; they have toxic effects on the immune system, reproductive system, and endocrine system by changing the metabolism of the body. To elucidate the underlying molecular mechanism, the clam Meretrix meretrix was exposed to 10 and 1000 ng/L Aroclor 1254 and natural seawater (control). Samples from clams exposed to natural seawater and those exposed to Aroclor 1254 for 1 and 3 days were individually collected for transcriptome analysis. After assembly, more than 535,157 transcripts with a mean length of 949 bp and an N50 length of 1279 bp were obtained; a final set of 177,142 unigenes was generated. In the present study, 5101 differentially expressed genes were identified. The differentially expressed genes were related to detoxification metabolism, oxidative stress, immune response, and endocrine system disruption. Of these genes, under the Aroclor 1254 exposure, cytochrome P450 20A1 (2.06–4.46 folds), glutathione S-transferase (2.25–3.80 folds), multidrug resistance-associated protein 1-like (1.49–2.92 folds), peroxidase-like protein (1.33–4.26 folds), lysozyme (1.61–2.05 folds), bcl-2 like 1 protein (1.14–2.29 folds) and vitellogenin (1.09–1.19 folds) showed been significantly induced expressed. At the same time, some genes were down regulated, including cytochrome P450 2J5 (−1.20 ~ −2.86 folds), cytochrome P450 3A24 (−1.40 ~ −4.08 folds), C1q (−1.27 ~ −1.66 folds), Sulfotransferase (−1.51 ~ −1.84 folds), monocarboxylate transporter 10 (−1.30 ~ −4.70 folds), 3-beta hydroxysteroid dehydrogenase (−1.43 ~ −2.81 folds) and beta-galactosidase (−1.23 ~ −2.23 folds). Furthermore, it showed that the expression levels of CYP2J5, glutathione S-transferase, 3-beta hydroxysteroid dehydrogenase and beta-galactosidase had time responses and dose responses. The present study provided insights into the toxic effects of Aroclor 1254 exposure in M. meretrix. • Dynamic transcriptomes in clam under Aroclor 1254 exposure were determined. • Detoxification metabolism, oxidative stress and immunity system were influenced. • The expression of Mct10, LRP2, 3β-HSD, VTG genes in clam had significant effected. • Aroclor 1254 exposure disrupted the thyroid hormone pathway in clam. [ABSTRACT FROM AUTHOR]

Microplastics ingested by two bivalve species Perna viridis and Meretrix meretrix collected from three estuaries viz. Ariyankuppam, Panithittu, and Chunnambar in Pondicherry, India was analysed for the first time in this research. Nile Red dye was used for microplastic detection. A survey of 50 local families was conducted to determine the frequency and quantity in which they consume mussels/clams. On an average, the number of microplastics per gram of soft tissue (wet weight) is 0.18 ± 0.04, 1.84 ± 0.61, and 1.76 ± 0.48; and the number of microplastics per bivalve is 0.50 ± 0.11, 1.75 ± 0.35, and 4.80 ± 1.39 respectively for Ariyankuppam, Panithittu, and Chunnambar. 61.02% and 77.42% of the particles belonged to the size group of <100 μm in M. meretrix and P. viridis respectively. A moderate positive correlation of r (18) = 0.6985, p < 0.05 was calculated between bivalve weight and microplastic particles. An average person belonging to the local community is likely to ingest 3917.79 ± 144.71 microplastic particles per year through mussel consumption. Unlabelled Image • Microplastic in Perna viridis and Meretrix meretrix was analysed using Nile red dye. • This is a first MP assessment for bivalves in three estuaries in Puducherry, India. • 50 families in the locality were surveyed to estimate the yearly mussel consumption. • Average MP/g soft tissue (wet weight) was higher in M. Meretrix than P. viridis. • Through bivalve diet, an average person in the locality is likely to uptake 3917.79 ± 144.71 MP. [ABSTRACT FROM AUTHOR]