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This study was aimed to optimise the Alcalase® enzymatic hydrolysis extraction of Asiatic hard clam (AHC) (Meretrix meretrix) protein hydrolysate in terms of hydrolysis time, hydrolysis temperature, hydrolysis pH, and concentration of enzyme. Protein hydrolysate produced from AHC (M. meretrix) meat was used to determine the optimum hydrolysis conditions. Hydrolysis of AHC meat was optimised using the Central Composite Design Response Surface Methodology (RSM) (CCD). The relationship between four parameters such as temperature (45 – 65°C), enzyme to substrate concentration (1 – 2%), hydrolysis time (60 – 180 mins), and pH (7.5 – 9.5) to the degree of hydrolysis was investigated. The optimum conditions for enzymatic hydrolysis of AHC meat to achieve the maximum degree of hydrolysis (DH) were observed at 65°C, enzyme to substrate concentration of 1%, hydrolysis time of 60 mins, and pH 7.5. The enzymatic protein hydrolysis of AHC meat was predicted using a two factors interaction (2FI) model. Under these optimum conditions, DH's predicted value was 97.41%, which was close to the experimental value (97.89%). The freeze-dried protein hydrolysate powder was characterized concerning the proximate composition. Proximate analysis revealed that the AHC meat contains 7.92±1.76% of moisture, 2.23±0.89% of crude fat, 1.98±0.82 of ash, and 10.53±0.04% of crude protein. While the Asiatic hard clam protein hydrolysate (AHCPH) composed 9.12±0.02% of moisture, 0.80±0.29% of crude fat, and 27.76±0.10% of ash. The protein hydrolysate produced also contained high protein content (50.09±0.88%) and may serve as a good protein source.

Odor is an important factor influencing the acceptance of clams by the consumer. In order to better understand the flavor characteristics of different clams, the volatiles in raw and cooked Meretri...

Highlight Identify the Vibrio bacteria Diversity of shellfish Vibrio bacteria (Meretrix Meretrix) Relationship similarity of Vibrio bacteria with MVSP 3.1 Program produces Dendogram Abstract Meretrix meretrix is one type of shellfish that is potential, and economic value, which high animal protein content as well as seafood that is widely consumed in Indonesia. This study aims to determine the diversity and similarity of Vibrio in M. meretrix at eduwisata mangrove Cengkrong Beach, Trenggalek. Isolation and identification of Vibrio was conducted by using the media TCBSA (Thiosulfate Citrate Bile Salt Sucrose Agar) streat plate through morphological observation, physiological and biochemical tests based Bergey’s Manual of Systematic Bacteriology conducted in the laboratory of Microbiology Faculty of Biology, Universitas Gajah Mada. Data analysis was performed using the MVSP (Multivariate Statistical Package) 3.1 in the form of a dendrogram showing the similarity relationship Vibrio bacteria. The results of the identification of Vibrio bacteria in M. Meretrix are V. herveyi, V. parahemolyticus, V. nereis and V. proteolyticus. V. herveyi has similarities with V. parahemolyticus 66% and 62% with V. proteolyticus while with V. nereis bacterium 54%.

Meretrix meretrix can accumulate heavy metals from the contaminated environment in its tissues and passed on these elements through the food chain, which can cause health hazards. The mean size distribution of the M. meretrix wild population at Batu Payung, Tawau, North Borneo, was determined by the linear morphometric analysis of outer shell length, and bivalve was categorized by the outer shell length size at 5-mm interval cluster groups. The selected heavy metals concentration in wild M. meretrix whole tissues was determined by an Induced Couple Plasma-Optical Emission Spectrometer (ICP-OES) to provide baseline data for policymakers and stakeholders to formulate sustainable harvest management. The largest group of outer shell size (45.00–50.00 mm) had the concentration of the least heavy metals in its tissues among other smaller shell size cluster groups, indicating M. meretrix outer shell length size of more than 45 mm cleanse excessive heavy metals out of their body more efficiently. A negative correlation between nonessential heavy metals (Cd, Pb) concentration in M. meretrix edible tissues and its outer shell length size signified that the largest group of outer shell size was safer to consume. M. meretrix is also facing overfishing like elsewhere in North Borneo.

In this study, the stability and flavor characteristics of nanoemulsions prepared with dextran-conjugated Meretrix meretrix clam protein isolate were studied by characterizing particle size, polydispersity index, zeta potential, turbidity, microstructure, e-tongue, e-nose and HS-GC-IMS. Compared with the NCPI (CPI nanoemulsions) and NCPI-Dex Mix (CPI-Dex Mix nanoemulsions), the NCPI-Dex Con (CPI-Dex Con nanoemulsions) has better stability and flavor. The breaking strength and breaking strain of clam sausages were significantly (P > 0.05) affected by the addition of NCPI-Dex Con. The gel strength with 8% NCPI-Dex Con was the highest (5122.08 g‧mm), a 51.07% increase compared with the control group (3390.58 g‧mm). The clam sausages supplemented with the 8% NCPI-Dex Con had the highest sensory score, with the densest and the most uniform gel structure. Therefore, CPI-Dex Con stabilized nanoemulsions could effectively improve the gel property and flavor of the clam sausages.

The present study was conducted in the Bakkhali river estuary, Cox’s Bazar, Bangladesh from September 2012 to July 2013. Percentage of protein was the main component of the biochemical composition in the mussels followed by carbohydrate, ash, and lipid.

Organophosphorus pesticides (OPs) play a certain role in promoting the development of agriculture and forestry, but they may cause potential harm to aquatic life when entering rivers and polluting water sources. Previous researches have shown that OPs participate in the regulation mechanism of aquatic organisms. Here, our aim is to determine the underlying mechanisms of one OP (dimethoate) at the transcriptional level using the clam Meretrix meretrix. 4119 DEGs were obtained from high-throughput RNA sequencing data. Then, expression profiles of some genes were verified by qPCR, which showed a positive correlation with the RNA sequencing results. 14,481 simple sequence repeats were also identified and could be further used as molecular markers. In addition, some oxidative, immune, and stress-related genes were further discussed and could also be used as biomarkers to indicate the biological response of dimethoate. This study will help to better understand the clam's response mechanism to dimethoate stress.

Information on the occurrence and bioaccumulation of bisphenols and benzophenones in coastal marine invertebrates is limited. In this study, concentrations of eight bisphenol and five benzophenone analogues were determined in 186 mollusks collected from coastal areas of the Chinese Bohai Sea during the period 2006–2015. Total concentrations of bisphenols and benzophenones were in range of not detected (nd)–58 (geometric mean: 13.0 ng/g) and nd–59.1 (2.06 ng/g) on a dry-weight basis, respectively. BPA and BPF were the major bisphenols, collectively accounting for >90% of the total concentrations. BP-3 was the predominant benzophenone, representing 74% of the total concentrations. The mollusk species, Meretrix meretrix, accumulated high concentrations of both bisphenols and benzophenones. A steady increase in bisphenol concentrations in mollusks was observed in recent years, whereas no obvious temporal trend was found for benzophenones. The estimated daily intakes of bisphenols through consumption of mollusks were lower than the current reference dose. This study establishes a baseline concentration for bisphenols and benzophenones in mollusks in Chinese coastal waters.

Paralytic shellfish toxins (PSTs) are notorious neurotoxins that threaten public health and food safety worldwide. Although PST monitoring programs have recently been established throughout China, the profiles and variation of PSTs in important commercial clams (e.g., Mactra veneriformis, Ruditapes philippinarum, and Meretrix meretrix) along the Jiangsu Province coastline remain largely unexplored. In this study, a validated hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) method was used to examine PST profiles and levels in 540 clam samples from natural production areas along Jiangsu Province coastline during 2014–2016. Although the PST levels (≤6.38 μg saxitotoxin equivalents (eq)/kg) were consistently below European Union regulatory limits (≤800 μg saxitotoxin eq/kg) during this time period, saxitotoxin, decarbamoylsaxitotoxin, and gonyautoxins 1 and 4 were detected, and nearly 40% of the samples were saxitotoxin-positive. The PST levels also varied significantly by seasons, with peak values observed in May during 2014–2016. This is the first systematic report of PSTs in clams from Jiangsu Province, and additional research and protective measures are needed to ensure the safety of clams harvested in this area.

Despite mass mortality, hard clams remain among the main cultured shellfish in Taiwan. Using cross-sectional data, this study applies threshold regression modeling with stocking density and feed costs as the threshold variables to explore the nonlinear relationship between input and output factors. The findings show that the production output levels may be increased by different combinations of factor inputs and variations in input factors. More specifically, the higher output levels may be achieved by increasing labor input while reducing capital input factors in farming households with a higher stocking density (HSD > 1,087,870 inds/ha) or higher feed cost (HFC > 13,889 NTD/ha). Farming households with a lower stocking density (LSD ≤ 1,087,870 inds/ha) may enhance production output levels by increasing feed input while reducing capital inputs. Moreover, the maximum output level of HSD and HFC farming households was estimated to reach 9255 kg/ha and 9807 kg/ha, respectively. Results of the production output simulation suggest that the feeding cost per hectare in LSD households should not exceed 25,119 NTD to avoid overfeeding, which may cause culture deterioration and lower survival rates. As such, farmers are advised to adjust their feed costs according to the stocking density to maximize production output.

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.

Carbon dioxide (CO2) capture by using calcium (Ca)-based adsorbents derived from natural wastes has attracted the attentions of many researchers nowadays. Utilization of these natural materials in CO2 capture is able to reduce the cost of the adsorbents and favor to the production cost. In this research, CaO-based adsorbents that derived from natural clam (Meretrix meretrix) shells and cockle (Anadara granosa) shells were modified for their properties through ethanol-water hydration treatment and studied for their performance in CO2 capture. The effect of ethanol concentrations in ethanol-water hydration treatment was investigated in order to identify the optimum ethanol concentration to achieve desired adsorbent properties and best performance in CO2 capture. Ethanol was found to have a role in expanding the pore structure of CaO sorbents in this study. Treated CaO-based adsorbents derived from shells were found to have a higher surface area and pore volume as compared to untreated samples. CaO-based adsorbent derived from clam shells and cockle shells treated with ethanol were found to achieve higher CO2 adsorption capacity at 13.72 mmol CO2 / g adsorbent and 16.57 mmol CO2 / g adsorbent, respectively, as compared to untreated clam shells and cockle shells, which recorded CO2 adsorption capacity of 7.95 mmol CO2 / g adsorbent and 9.61 mmol CO2 / g adsorbent, respectively. This was corresponded to the higher surface area of the treated adsorbent samples, which promoted the CO2 adsorption activity.

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.

To evaluate the pollution level of marine environment received treated municipal effluent (TME), the water quality classification index (WQCI) capable of integrating biomarker results into a four-level pollution for effluent assessment was proposed and applied. The WQCI calculation was that of the integrated biomarker responses vesion 2 (IBRv2) index based on the expert system classification scale. In this research, mussels of Meretrix meretrix were treated with different effluent volume ratios (EVRs, 0–40%, v/v) for 12 days, six biomarkers of oxidative stress, metal exposure and neurotoxicity in both gills and digestive glands as well as the other two biomarkers of general health and genotoxicity in hemocytes were measured. Then based on the correlation analysis between the response of biomarkers and EVRs, the lysosomal membrane stability (LMS) and micronucleus frequency (MF) in hemocytes, glutathione (GSH) and acetylcholinesterase (AChE) in gills were chosen to calculate the IBRv2 and WQCI. The results showed that the control (EVR = 0%) was defined as Level I, EVR of 1–5% as Level II, EVR of 10–30% as Level III, and EVR of 40% as Level IV. In addition, two other sets of data of biomarkers in previous studies were used to test the applicability of the classification scheme established. The WQCI values and the evaluation results based on them were almost identical to those obtained by using the first set of data. This study is the first attempt to develop an index on water quality assessment of marine environment received discharged effluent from a biological perspective. The findings confirm that WQCI offers a potential measurement of water quality evaluation of marine environment and possible to be a water quality standard.

Meretrix meretrix, Pholas dactylus and Babylonia spirata are potential fisheries commodity, but information about their nutritional values is still limited. This research was aimed to determine the chemical compositions of Meretrix meretrix, Pholas dactylus and Babylonia spirata. Proximate of Meretrix meretrix, Pholas dactylus and Babylonia spirata were analyzed using thermogravimetric, soxhlet and kjeldahl methods. Their amino acid composition and taurine content were analyzed using High Performance Liquid Chromatografy (HPLC). The moisture, ash, fat, protein and carbohydrate contents of Meretrix meretrix were 79.98%, 1.37 0.11 9.39 and 9.02 respectively; Pholas dactylus were 83.78%, 1.19, 0.11, 11.37 and 3.55 respectively; while Babylonia spirata 78.44, 1.20, 0.33, 17.38 and 2.65 respectively. Arginine was the highest essential amino acid found in Meretrix meretrix, Pholas dactylus and Babylonia spirata meat with values of 1.12%, 0.93 dan 2.50 respectively. Glutamic acid was the most abundant non-essential amino acid with the highest value of 2.24, 2.14 and 3.76. The limiting amino acid was histidine with the value of 0.25%, 0.18 and 0.34, respectively. The taurine content of Pholas dactylus meat (0.085%) was higher than the Babylonia spirata and Meretrix meretrix (0.067 and 0.062%, respectively).

To understand the delicious taste of the clam M. meretrix Linnaeus, the putative umami peptides from the aqueous extract of the cooked clam were obtained by ultrafiltration, gel filtration chromatography, and reversed-phase high-performance liquid chromatography. The isolated peptide fraction with the most intense umami taste was screened by sensory and electronic tongue analysis. Seven novel peptides, GLLPDGTPR, RPNPFENR, STMLLESER, ANPGPVRDLR, QVAIAHRDAK, VLPTDQNFILR, and VTADESQQDVLK, were identified and synthesized to verify their taste characteristics. The taste activity prediction and the sensory evaluation of the synthetic peptides revealed that those peptides were umami and umami-enhancing peptides. Docking of the synthesized peptides with the umami taste receptor T1R1/T1R3 indicated that the peptides could enter the binding pocket in the Venus flytrap domain of the T1R3 cavity, wherein Asp196 and Glu128 may play key roles in the synergism of umami taste and hydrogen bonding and electrostatic interactions are important interaction forces.

Microplastic pollution is a problem that is currently attracting the attention of various groups, from scientists to ordinary people. This type of pollution can have a negative impact on aquatic biota, especially organisms that have filter feeder behavior. Asiatic hard clam (Meretrix meretrix) is a filter feeder organism that has a considerable risk of being exposed to microplastics. This study aims to analyze the concentration of microplastics in Asiatic hard clam (M. meretrix) at Lemo Beach, Burau District, East Luwu Regency, South Sulawesi. Sampling was performed using purposive random sampling method. The number of samples of Asiatic hard clam was 118 which were divided into three groups of shell length, namely class A (2.75 - 3.40 cm), class B (3.41 - 4.21 cm), class C (4.22 - 5.24 cm). Observation of microplastic particles is carried out using a stereo microscope equipped with a camera (Miconos optical lab). The results of the frequency analysis of the presence of microplastics in the clam showed that class A was the class with the highest frequency, namely 95.67%. The observed microplastics were in the form of fibers, fragments, and films with a predominantly black and transparent color. The size of the observed microplastics ranged from 0.033-0.88 mm. The results of the microplastic concentration analysis showed that size class A had a greater concentration than class B and class C.

The objective of this study was to develop an analytical method for protecting Jiaozhou Bay clam (Ruditapes philippinarum) with Protected Designation of Origin (PDO). The R. philippinarum samples were collected from three major producing areas (Jiaozhou Bay, Nantong coast, and Dalian coast) in China, and the Meretrix meretrix samples were from Nantong coast in May and September 2014. The contents of 46 elements in all clam samples were determined by inductively coupled plasma mass spectrometry. The obtained data were analyzed using analysis of variance, principal component analysis, and stepwise linear discriminant analysis. The results showed that both the geographical origin and season affected elemental contents in R. philippinarum. Seven elements (Mg, Cd, Sn, Sb, Cs, Ba, and U) independent of seasonal variation were selected as good indicators for discriminating the geographical origin of clams. Based on the discriminant models built with these seven elements, the predictions of the geographic origin gave an overall correct classification rate of 100.0 % and a cross-validation rate of 97.2 %. In addition, R. philippinarum and M. meretrix had their own elemental fingerprinting patterns and could be distinguished. Therefore, the multi-element analysis combined with multivariate statistics can be used for the identification of Jiaozhou Bay clam with PDO.

Bivalvia is one of the organisms that is able to accumulate heavy metal content in the body. Lead heavy metal (Pb) is a heavy metal that is toxic if the level exceeds the safe limit that has been set both on the body of an organism or in humans. The purpose of this study was to determine the various types of bivalves found in Bangkalan Coastal Madura Island, and to analyze the content of lead heavy metals (Pb) in bivalve bodies found in the region. This research is observational. Sampling was carried out by hand sorting, then identified the type of bivalves that were obtained and then the samples were taken to the laboratory for testing using the Atomic Absorption Spectrophotometer (AAS). The results of the study are known that, the types of bivalves found and identified in the Bangkalan Coastal area of Madura Island are Bamboo Scallops (Solen sp.), Blood Scallops (Anadara granosa), Sweet Scallops (Meretrix meretrix), and Stone Scallops (Placamen isabellina). Laboratory test results of lead heavy metal content (Pb), it is known that each clam accumulates lead heavy metal (Pb) with different amounts of concentration, wherein the heavy metal content of lead (Pb) in Bamboo / Lorry Shells (0.168-0.208 ppm) , Blood Shells (0.152-0.231 ppm), Sweet Shells (0.161-0.288), and Stone Shells (0.143-0.169 ppm), and it is known that the heavy metal content of lead (Pb) of the four bivalves is still below the threshold level of metal contamination according to Kep. Ditjen POM No. 03725/B/SK/VII/1989 which determines that the maximum limit of lead (Pb) heavy metal content in marine organisms is 2 ppm.

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 of100 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.

High temperature has significant effects on the survival and immunity of organisms. In order to conduct a detailed investigation into the response of the saltwater clam Meretrix meretrix from different geographical populations (GuangXi, JiangSu, ShanDong, LiaoNing) to high temperatures, we examined the survival rates and antioxidant enzyme activities of these clams that were exposed to different temperature treatments (25°C, 35°C, 37.5°C, 40°C). Results showed that the survival rate of clams from GuangXi was highest at 40°C, followed by JiangSu. SOD and CAT activities of all the clams increased with the increasing temperatures, and then gradually decreased at 40°C over time. The expression levels of Hsp70 of M. meretrix from four populations were analyzed by qPCR sampled from the hepatopancreas after 72 h under different temperatures. Higher Hsp mRNA expression of GuangXi at 40°C indicated that clams of GuangXi have stronger high temperature resistance than those of the other geographical populations. Our findings provide a basis for the choice of cultured clams with a high temperature tolerance.

In this study, a sensitive and rapid method for the simultaneous quantification of 17 nucleosides and nucleobases and 23 free amino acids in clam samples using ultra-fast liquid chromatography coupled with tandem mass spectrometry (UFLC-MS/MS) was developed. Sufficient separation of 40 analytes was achieved on an Acquity BEH Amide column (2.1 mm × 100 mm, 1.7 μm) in a single run of 15 min. The overall limits of detection (LODs) and limits of quantification (LOQs) were between 0.05~38.8 and 0.15~128 ng/mL for the 40 analytes, respectively. The newly developed method was validated and subsequently applied for the analysis of the content variation of 40 analytes in four commercial clam species (Mactra veneriformis, Ruditapes philippinarum, Meretrix meretrix, and Cyclina sinensis) collected monthly from January to December 2014 at the coast of Jiangsu, China. Significant seasonal variation was observed for most analytes. Major nucleosides and nucleobases were at their highest contents in June or July, the contents of free amino acids showed the same pattern. Thus, if high concentrations of these functional small molecules are desired, Jiangsu native clams should be harvested in early summer. The results suggest that the present UFLC-MS/MS method could be employed as a useful tool for quality assessment of the clam samples as well as other food samples using nucleobases, nucleosides, and free amino acids as markers.

This paper presents results of a laboratory study designed to assess the impact of pollution in Espirito Santo Estuary, Mozambique, by the use of scope for growth (SFG) and condition indices in the clam Meretrix meretrix . Low energy balances were observed at all sites from the estuary (0.91–2.89 J h −1 g −1 ) as well as from the comparison site (2.57 J h −1 g −1 ). Lowest condition index was observed in clams from the comparison site. Results from the present study indicate symptoms of stress and impact of pollution, and whether M. meretrix is a suitable candidate species for further studies of environmental contamination in coastal regions. This study is to our knowledge the first to investigate the energy available for growth in M. meretrix in its southern area of distribution.

Color polymorphism has received much attention due to its strong implications for speciation and adaptation. In contrast to body color, little is currently known about the molecular mechanism of shell color formation. This study represents the first analysis of the relationship between whole-scale gene expression and shell color variations in the marine bivalve mollusks via comparative transcriptome analyses. Three clam Meretrix meretrix strains with different and monotonous shell color patterns, which were developed by our 10-year artificial selection, combined with clams with nearly white shell color were used in the analyses. The results supported the idea that there was a relationship between gene expression and shell pigmentation in the clam M. meretrix, and complex signal transduction were involved. It was proposed that Notch signaling pathway played a crucial role in shell pigmentation in a gene-dosage dependent pattern and also potentially involved in the shell color patterning. Calcium signaling process may equally be implicated in shell color formation via activation of Notch pathway. Other differentially expressed genes (e.g., Myl, Mitf) potentially implicated in shell color pigmentation were also noticed. This study provides information on the expression profiles of clams with different shell color morphs and sheds light on color formation mechanism of shell.

A 3×3 complete diallel cross comprising three families of the clam Meretrix meretrix (P1, P2 and P3) was used to determine the combining ability of parental families and heterosis of F1 under indoor and openair environments for growth traits. Analysis of variance for shell length and whole body weight indicated highly significant cross effects, environment effects and the interaction of cross by environment. General combining ability (GCA) and specific combing ability exhibited great variation among crosses and between two environments. Pooled over environments, P2 was the top combiner among the three parental families for both traits studied. The cross of P1 and P3 had the highest SCA. Additionally, significant reciprocal effects were observed. For individual environment, about half of the crossbred combinations showed favorable Mid-parent heterosis (MPH) (>1%) for the shell length and whole body weight. Our data has shown that non-additive genetic and reciprocal effects constituted the major sources of genetic variation for both shell length and whole body weight, which indicates that crossbreeding among selective families could further explore the heterotic effects.

Unbalanced parental contribution and small effective population size (N (e)) are common issues during the artificial breeding of marine bivalves. The impact of hatchery-spawning practices on parental contribution, effective population size, the N (e)/N ratio, and genetic diversity are largely unknown. To address this, we conducted a parentage analysis on a complete 3x3 diallel cross of clam M eretrix meretrix using eight microsatellite markers. The genetic diversity of the parents was higher than that of their respective offspring in most crosses (8/9). Sires or dams from the same family contributed unequally to the pool of offspring from a particular cross, and the same parent clam exhibited large variation in parental contribution among different crosses. The variance in male contribution was higher than that of the female contribution in most crosses, suggesting that male contribution was more skewed than for females. The N (e)/N ratio for nine crosses ranged from 0.58 to 0.86. There was no linear relationship between the sex ratio and the N (e)/N ratio (P > 0.05). Moreover, a sex ratio closer to one-to-one does not necessarily mean a larger effective population size. A solution to small effective population size in commercial breeding programs is increasing broodstock numbers and attempting to maintain a balanced sex ratio.

Carbonated hydroxyapatite (CHAp) derived from three different shells, Cerastoderma edule, Paphia undulata, and Meretrix meretrix shells, have been synthesized by precipitation method. Calcium oxide from extracting shells, diammonium hydrogen phosphate, and ammonium bicarbonate was used to synthesis as the starting precursors. The CHAp materials were analyzed by Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared (FT-IR), and X-Ray Diffractometer (XRD). EDS analysis showed that the Ca/P ratio of CHAp powders were around 1.75-1.77 (bigger than the Ca/P ratio of HAp) and carbonate content of the powder CHAp was 3.10-4.05wt%. XRD data has produced diffraction patterns from the three different shells similar to the apatite structure. The position of the main peak (2θ) diffraction patterns detected at 31.99°, 32.23°, and 31.95°. The lattice parameter of a-axis and c-axis were obtained around 9.37 Å and 6.89 Å. Crystallite size of CHAp samples was 30-40 nm. The FTIR spectra showed that there are functional groups of OH-, PO4 3-, and CO3 2- at wave number around 3447, 571, and 873 cm−1. Based on the results of the analysis, it shows that the CHAp characteristics that had successfully produced from Cerastoderma edule, Paphia undulata, and Meretrix meretrix shells were B-type CHAp.

Asiatic hard clam (Meretrix meretrix) was one of molluscs (bivalve) with economical value. However, fishing activities were presumed to cause a decline in population. This condition was strengthened by the size of the clam which became smaller nowadays. The purpose of this study was to determine spatial distribution of M. meretrix, length distribution, and length-weight relationship. The study was conducted at 3 stations, consisted of Station I at Asahan River estuary which was located by mangrove forest, Station II at the sea and Station III at the waters near mainland of Batu Bara Regency. Estimation growth of M. meretrix was examined following FISAT II method. The density of M. meretrix was dominant at Station I which was low in salinity and high in organic matter. The class interval of 23-34 mm at station I dominated length distribution. Length-weight relationship was found to be very strong with determinant value approaching

This study aims to determine the effect of the methanol extract of sea water clams (Meretrix meretrix) against blood chemistry profile in vivo in Sprague Dawley rats. After three months fed by two different methanol extract concentration i.e. 0.1 g. kg−1 body weight (M/0.1) and 1 g. kg−1 body weight (M/1), blood serum has been taken prior for the analysis using Biocon Diagnostic test kit quantitatively. Based on the observations, growth, feed intake, weight of liver and kidney were found in normal conditions. When comparing urea, creatinine and cholesterol extents among the control and treated mices were not significantly different (p>0.05) while the levels of bilirubin and albumin between control rats treated with M/0.1 and M/1 results in different significantly (p

A breeding-selection program for the clam, Meretrix meretrix, was conducted since 2004. Two of the selection populationswere generated with the shell color pattern as an additional selection criterion and named as SP (purple stripes) population and SB (black dots) population. The third-generation SP and SB populations (08G3SP and 08G3SB, respectively) were cultured at two commercial clam farms and a nursery pond and their shell lengths were compared. 08G3SB clams had significantly larger sizes than 08G3SP clams at commercial clam farms (p < 0.05), yet 08G3SB individuals were significantly smaller than 08G3SP individuals at the nursery pond (p < 0.05). Then, we examined the growth of the fourth-generation SP and SB populations (10G4SP and 10G4SB, respectively) at a commercial farm, and found that the shell lengths of the 10G4SB clams increased at a significantly higher growth rate than the 10G4SP clams (p < 0.05) from May to September, when the water temperature was between 24.2-27.5A degrees C, while 10G4SB lost the growth advantage in the other months. These results indicated that SP and SB populations responded differently to environmental factors, so it is beneficial for the clam farmers to select a suitable population according to the culture environment. Furthermore, a diallel mating of the SB and SP populations was designed to investigate whether their hybrid population would show heterosis. However, the heterosis was not shown in this study, whichmight result from the slight genetic divergence between SB and SP populations.

The hard clam (Meretrix meretrix) is a commercially important maricultured shellfish in China. The transcriptome data of M. meretrix provided a valuable resource to mining large amount of EST-SSR markers quickly and cost-effectively. Here we isolated and characterized 53 novel polymorphic EST-SSR markers in 30 individuals. The number of alleles varied from 2 to 8, with an average of 4.19 alleles per locus. The observed and expected heterozygosities ranged from 0.040 to 1.000 and from 0.040 to 0.799, respectively. Thirty-one loci significantly deviated from HWE (P < 0.01) after Bonferroni correction. Interspecific transferability revealed that 19 polymorphic loci in Meretrixlamarckii and 10 in Meretrix lyrata were firstly characterized. These novel polymorphic SSR markers will be particularly useful for further diversity analysis, evolutionary studies, genetic trait mapping and marker assisted selection.

The research goal was to compare the shells types of Kapah (Meretrix meretrix; M. lyrata; Geloniacoaxans) that found in the Coast Binalatung area, Tarakan and to assess the growth of shellfishallometri. Sampling is done by making a transect along the coast Binalatung as much as 12 transects.Each transect arranged lengthwise along the beach with 25 meters of each transect. Sampling wascarried out in the absence of repetition with an area of 25 x 25 meters transect. Sampling was done byusing tools such as Kapah’ rakes. The result showed the M. meretrix constistes of 63 % of Kapah’spopulation while M. lyrata and G. coaxans represent 27 % and 10 % respectively. Growth comparisonbetween shell length and weight was considered as positive allometri while comparison between thickshells and weight of shellfish Kapah was allometri negative.Keywords: shellfish kapah, allometri growth, Binalatung, Tarakan

This study investigated accumulation of Escherichia coli and aerobic colony count in three types of shellfish species. The results indicated that the capability of accumulating E. coli and aerobic colony count for Sinonovacula constricta was stronger than that for Meretrix meretrix and Tegillarca granosa, and capability of accumulating E. coli for M. meretrix was slightly stronger than that for T. granosa. However, no significant difference was observed in the capability of accumulating aerobic colony count between M. meretrix and T. granosa. Moreover, accumulation of E. coli in S. constricta is affected by contaminated seawater and E. coli were accumulated much faster and more in S. constricta when the seawater contaminated more serious. Meanwhile, the results suggested that the populations of E. coli in S. constricta changed in accordance with the weather. This is the first study to investigate the differences of accumulating E. coli in three types of shellfish species.

Mere15 is a novel antitumor polypeptide purified from Meretrix meretrix Linn. (Veneridae). Previous studies have shown that the polypeptide induced cell death via intrinsic mitochondrial pathway.In the present study, the effects of Mere15 on cell adhesion, migration, invasion, as well as secretion and expression of matrix metalloproteinases (MMPs) were studied in human lung adenocarcinoma A549 cells.The effect of Mere15 on cell adhesion, migration and invasion were studied by cell adhesion and transwell assay. The expression of MMPs was determined by gelatin zymography and RT-PCR analysis.The ability of cell adhesion was decreased by 86.74% at the concentration of 12.0 μg/mL of Mere15. And the migration and invasion of A549 cells were decreased with the inhibition ratio of, 69.22 and 53.84% when treated with 15.0 μg/mL of Mere15. Further study also revealed that treatment of the cancer cells with Mere15 (15.0 μg/mL), the secretion of MMP-2 and MMP-9 were down-regulated with the inhibition ratio of 72.00 and 93.24% and the inhibition rate of mRNA expression of MMP-2 and MMP-9 was 57.54 and 91.22%, respectively.The study demonstrates that Mere15 inhibits tumor growth via both pro-apoptotic and antimetastasis pathways, and the polypeptide has potential to be developed as a multi-target therapeutic agent for the treatment of human lung cancer.

Because of the high frequencies of null alleles at microsatellite loci in mollusks, it is difficult to enhance the accuracy of parentage assignment in closely related families by increasing the number of loci. To develop an effective approach, microsatellite markers combined with mitochondrion COI marker were used for parentage assignment with computer simulations and experimental verification in the clam, Meretrix meretrix. In the present study, simulations based on allele frequency data from the candidate parents (sample II) demonstrated that combined exclusion probability of the five microsatellite loci (0.991 for Excl 1 and 0.995 for Excl 2) were not much lower than that of the seven loci (0.993 and 0.999). After discarding the two loci that deviated from Hardy-Weinberg equilibrium in experimental verification, accurate probability of progeny assigned to their fathers and mothers with both parents unknown was 68% and 59% in CF (closely related families), and 76% and 68% in DF (distant related families), respectively, which were much lower than those predicted by the simulations. When the COI marker was used in combination with microsatellite markers, 32 out of 39 offspring that were not previously assigned to their correct parents were assigned to their correct mothers, and 29 doubtful offspring could be assigned to their correct fathers. Consequently, with the combination of the two kinds of markers, the accurate probability of progeny that can be correctly assigned to their true fathers and mothers was increased to 89% and 92% respectively. We suggest that the use of microsatellite markers and COI marker will greatly improve the efficiency of parentage determination in closely related families in the clam. (C) 2011 Elsevier B.V. All rights reserved.

We described and characterized 17 expressed sequence tag (EST)-derived simple sequence repeats (SSR) and 16 genomic-derived SSRs for the clam Meretrix meretrix. The EST-SSRs comprised 17.6% dinucleotide repeats, 35.3% trinucleotide repeats, and 47.1% tetranucleotide repeats; whereas the majority of the G-SSRs were dinuleotide repeats (75.0%). The number of alleles for the 33 SSR markers varied from 6 to 15, with a mean of 10.3 alleles per locus. Observed and expected heterozygosity (Ho and He) varied from 0.613 to 0.824, and 0.687 to 0.850, respectively. Polymorphic information content (PIC) ranged from 0.645 to 0.842. The mean values of number of alleles, Ho, He, and PIC of G-SSRs were higher than those of the EST-SSRs. No significant deviations from Hardy-Weinberg equilibrium or linkage disequilibrium were observed in the 33 loci. These loci are the first to be characterized in M. meretrix and should be useful in the investigation of genetic evaluation for conservation.

A total of 2,970 EST-SSRs (2.38%) were identified by transcriptome sequencing of clam Meretrix meretrix (751,970 reads, similar to 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.

The hard clam (Meretrix meretrix) is a popular edible shellfish in South and Southeast Asia, being heavily exploited by hand dredging in Marudu Bay, Malaysia. The current study was performed to evaluate the shell damages caused by this artisanal dredging gear. Samplings were conducted in triplicates at two sites using both hand dredging and hand collecting (control) sampling methods. The shell length and total weight, damage areas and breakage patterns of each clam were recorded. A questionnaire survey was conducted with local bivalve harvesters to gather information on the fishing pressure in Marudu Bay. Results revealed that the efficiency (fishing yield) of hand dredging gear was three times higher than hand collecting. However, hand dredging gear causes lethal shell damages to small hard clams (

Wild clams of Meretrix meretrix and Cyclina sinensis were collected from intertidal flats of Shuangtaizi estuary during low tide in 2016. Morphometric traits including shell length (SL), shell height (SH), shell width (SW), and total body weight (TW) of the clams were measured. Correlation, path, and regression analyses were conducted to evaluate the relationship between morphometric traits and total body weight and determine the optimal indices for artificial breeding of M. meretrix and C. sinensis. Significant differences in correlation coefficient among various characteristics were found. Shell height and SW showed the strongest influence on total body weight. The optimal regression equation of the measured traits was established in both clams by using a stepwise regression method: TW = –27.404 + 0.948 SW + 0.422 SH + 0.291 SL for M. meretrix and TW = –36.965 + 1.107SH + 0.564SW for C. sinensis. These results provide baseline information for selective breeding and conservation management of the two commercially important clam species in Shuangtaizi estuary.

The hard clam Meretrix meretrix, which has been traditionally used as medicine and seafood, was used in this study to isolate antioxidant peptides. First, a peptide-rich extract was tested for its protective effect against paraquat-induced oxidative stress using the nematode model Caenorhabditis elegans. Then, three novel antioxidant peptides, MmP4 (LSDRLEETGGASS), MmP11 (KEGCREPETEKGHR) and MmP19 (IVTNWDDMEK), were identified and were found to increase the resistance of nematodes against paraquat. Circular dichroism spectroscopy revealed that MmP4 was predominantly in beta-sheet conformation, while MmP11 and MmP19 were primarily in random coil conformation. Using transgenic nematode models, the peptides were shown to promote nuclear translocation of the DAF-16/FOXO transcription factor, a pivotal regulator of stress response and lifespan, and induce the expression of superoxide dismutase 3 (SOD-3), an antioxidant enzyme. Analysis of DAF-16 target genes by real-time PCR reveals that sod-3 was up-regulated by MmP4, MmP11 and MmP19 while ctl-1 and ctl-2 were also up-regulated by MmP4. Further examination of daf-16 using RNA interference suggests that the peptide-increased resistance of C. elegans to oxidative stress was DAF-16 dependent. Taken together, these data demonstrate the antioxidant activity of M. meretrix peptides, which are associated with activation of the stress response factor DAF-16 and regulation of the antioxidant enzyme genes.

Three wild populations of Meretrix meretrix sampled from Dongxing, Beihai, and Shankou along the coast of Guangxi, China, were investigated with morphometry and karyometry. Six morphological indices (shell length, shell height, shell width, hinge length, total wet weight and shell weight) were measured. Differences in all morphological indices except hinge length were significant among the three populations (P 0.05). However, the order of metacentric, submetacentric and subtelocentric chromosome pairs was variable among the three populations. The results indicate a high level of inter-population variation in morphology and karyotype.

All structural biological materials are nearly composite materials and often exhibit some superior properties. In order to obtain useful information for the design and manufacture of composite materials, the microstructures and the friction-wear properties of three species of bivalve shells were studied in this paper. The results showed that the microstructure of tested bivalve shells I ( Meretrix meretrix ) and II ( Saxidomus purpuratus ) are constructed of about 10–100 μm small platelets stacked in brick-and-mortar fashion and small platelets consist of lamella clusters. The lamellae are parallel inside the individual cluster. The orientations of adjacent lamellae clusters form the angle of about 70–90°. The thickness of lamellae is about about 0.2–0.6 μm. The organic component and the calcium carbonate form the three-dimensional net-like microstructure, respectively, which interlaces each other to form the microstructure of the bivalve shells. The microstructure of bivalve shells III ( Periglypta chemnitzii ) is constructed of about 10–40 μm particles with the internal structure of lamellae clusters as the above mentioned. Under the experimental conditions of medium-carbon steel counterpart and sliding dry friction, the friction coefficient of the bivalve shells is lower than that of grey cast iron HT200. The organic component of the bivalve shells can transfer to the friction interface and form organic film, which not only lubricates the friction interface but also protects the friction surface. The organic component is very important to the friction-wear property of the shells.

Meretrix meretrix L. was held in the laboratory under simulated natural conditions to measure specific physiological parameters of its energy budget. O2 consumption rate, NH3 excretion rate (NR), ingestion rate, faeces excretion rate and scope for growth (SFG) were negatively related in an exponential manner to the fresh weight of the clams at all water temperatures, while almost all metabolic rates of the clams were positively related in an exponential or e-exponential manner with water temperature. However, the co-relationship between metabolic rates and water temperature was not as close as that between metabolic rates and fresh weight of the clam. The combined effect of fresh weight and water temperature was observed on all metabolic rates except for NR and SFG. At all culture temperatures and for all fresh weights of clams used, respiration took the largest percentage of ingested energy (41.5–51.2%), faeces excretion was second (31.0–42.3%), growth third (12.1–15.5%) and urine production last (2.1–5.6%).

A nature-simulating culture system was used to explore the influence of salinity, the diurnal cycle and daylength on ingestion rate (IR) and assimilation efficiency (AE) of Meretrix meretrix . The clams used in the experiments were grouped into three sizes: small, with a shell length of 2.70 ± 0.10 cm and a dry fresh weight of 0.35 ± 0.04 g; medium, with a shell length of 4.00 ± 0.05 cm and a dry fresh weight of 1.25 ± 0.05 g; and large, with a shell length of 5.00 ± 0.10 cm and a dry fresh weight of 2.45 ± 0.10 g. The clams in all size groups demonstrated a common response pattern in IR and AE under salinities ranging from 18 to 34 ppt. The clams achieved the greatest IR within the salinity range 27 to 30 ppt. There was a marked reduction in IR outside this range. Of the salinities tested 18 ppt was the harshest stress to the feeding of M. meretrix . Between the salinities 24 to 34 ppt, changes in AE of the clam were the inverse of those observed in IR, suggesting that M. meretrix is able to compensate for the loss of IR by an increase in AE. Although the effect of both salinity and body size of the clam was significant on both IR and AE, salinity had evidently stronger influence than body size. All sizes of clam showed a three-phase diurnal feeding pattern: a high ingestion phase from 00:00 to 08:00, a low ingestion phase from 12:00 to 20:00, and a changing phase between low and high ingestion phases. The IR response to daylength comprised a high and constant feeding phase at daylengths from 0 to 16 h (longer darkness) and a declining and unstable feeding phase as daylength increased from 16 to 24 h (shorter darkness). All sizes of clams demonstrated an inverse adaptation to AE compared with IR, indicating that the clam is able to achieve a stable feeding physiology by compensating for daylength-induced variations in IR by changing AE. The ANOVA analysis also showed that both diurnal cycle and daylength affected IR and AE of the clam very significantly, body size did not, however.