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The dynamic regulation of ions and amino acids in the gills and mantle of the Asian hard clam, Meretrix lusoria, following the exposure to a hyperosmotic environment was hitherto unclear. The present study revealed that the osmolality as well as the Na+ and Cl– concentrations in the hemolymph were significantly increased 3 h after transferring the clams from an environment with the salinity of their natural habitat (brackish water; BW; 20‰) to one with hyperosmotic salinity (seawater; 35‰). In addition, we found that the specific activities of Na+/K+-ATPase, a key enzyme that plays a significant role in cell osmoregulation, in the gills and mantle of clams were significantly increased at 72 and 12 h post-transfer, respectively, during acclimation to hyperosmotic salinity. Similarly, the contents of free amino acids (FAAs) such as taurine, alanine, and glycine were significantly elevated during hyperosmotic salinity acclimation. Previous research indicates that taurine is the most abundant FAA in the gills and mantles of Asian hard clams and that the taurine transporter (TAUT) plays an important role in taurine accumulation. The present study showed that TAUT mRNA and protein expression were significantly and transiently increased in the mantle of Asian hard clams following exposure to seawater; although the expression of TAUT mRNA in the gills of Asian hard clams was also transiently stimulated by exposure to hyperosmotic salinity, the relative TAUT protein abundance decreased only at later stages. Accordingly, the findings of this study improve our understanding of the dynamic processes of ion and amino acid regulation in the peripheral tissues of bivalves under hyperosmotic stress.

The microwave-assisted induction heating (MAIH) method—an emerging thermal technique—was studied to heat the prepackaged raw hard clam (Meretrix lusoria). The cooking effects on microbial and physiochemical qualities of clam were investigated. After the heating of the clam meat samples, the aerobic plate count (APC), psychrotrophic bacteria count (PBC), and total volatile basic nitrogen (TVBN) levels decreased with increasing heating time, but the shucking ratio, area shrinkage, and texture (hardness, cohesiveness, and chewiness) increased. In addition, the L* (lightness) and W (whiteness) of the clam meat samples increased significantly at the beginning of the heating period, whereas they decreased significantly with extended heating time. However, a* (redness) had the opposite trend. This study found that when clams were heated for more than 120 s at 130 °C or 150 s at 90 °C, they displayed obvious shrinking and a yellow-brown appearance, indicating that they are overcooked. After heating by MAIH for at least 110 s at 130 °C or 130 s at 90 °C, the samples were cooked well and gains a completely shucking, along with no microbial count detected. Therefore, the results indicated that the optimum heating conditions for prepackaged hard clams subjected to an MAIH machine were 130 °C for 110 s or 90 °C for 130 s.

Microplastics have already been detected in various human foods, especially seafood. This problem should be especially pertinent to the Taiwanese public because a relatively high proportion of people&rsquo, s diet comes from seafood. Therefore, a pilot study of microplastic contamination of seafood products commonly consumed by Taiwanese people is presented. Six batches of three seafood species were examined for the presence of microplastics using FTIR spectroscopy. A total of 107 seafood individuals from three species (hard clam Meretrix lusoria, oyster Crassostrea gigas, Loligo squid Loliginidae spp.) weighing a total of 994 g yielded a total of 100 microplastic particles consisting of nine different polymer types. The most common polymer types were polypropylene, poly(ethylene:propylene:diene), and polyethylene terephthalate, we also detected six additional, but less common polymer types. A total of 91% of microplastic particles were fragments that likely originated from fragmented plastic debris which was then consumed by the seafood species, the remaining particles were fibers and a pellet. The mean number of microplastics kg&minus, 1 was 87.9 microplastics kg&minus, 1 across the three examined species. Given that the Taiwanese public average about 10 kg of seafood consumption per year, a few thousand microplastic particles are estimated to be annually consumed on average. The methodology of this pilot study can now be used to conduct examinations of more seafood species and samples.

Bivalves, such as freshwater clams (Corbicula fluminea) and hard clams (Meretrix lusoria), are the most extensive and widely grown shellfish in land-based ponds in Taiwan. However, few studies have examined the contamination of bivalves by quinolone and organophosphorus insecticides. Thus, we adapted an established procedure to analyze 8 quinolones and 12 organophosphorus insecticides using liquid and gas chromatography&ndash, tandem mass spectrometry. Surveys in Taiwan have not noted high residual levels of these chemicals in bivalve tissues. A total of 58 samples of freshwater or hard clams were obtained from Taiwanese aquafarms. We identified 0.03 mg/kg of enrofloxacin in one freshwater clam, 0.024 mg/kg of flumequine in one freshwater clam, 0.02 mg/kg of flumequine in one hard clam, 0.05 mg/kg of chlorpyrifos in one freshwater clam, 0.03 mg/kg of chlorpyrifos in one hard clam, and 0.02 mg/kg of trichlorfon in one hard clam. The results indicated that 5.17% of the samples had quinolone insecticide residues and 5.17% had organophosphorus residues. However, the estimated daily intake (EDI)/acceptable daily intake quotient (ADI) indicated no significant risk and no immediate health risk from the consumption of bivalves. These results provide a reference for the food-safety screening of veterinary drugs and pesticides in aquatic animals. Aquatic products should be frequently screened for residues of prohibited chemicals to safeguard human health.

Marine bivalve mollusks were obtained from 13 collecting sites, intertidally on beaches and from fishing nets in ports, along the coast of Gangwon Province, Korea. A total of 70 species belonging to 27 families were encountered; all species are illustrated with photographs. Among them, 17 species are recorded for the first time for Gangwon-do, and two species are new records for Korea: Gari chinensis Deshayes, 1855 (Psammobiidae) and Clinocardium likharevi (Kafanov in Scarlato, 1981) (Cardiidae). Taxonomic and distributional comments on 13 species are provided, and the biogeography of the area is discussed. Some warm-water species of bivalves [e.g. Anadara talmiensis (Kalishevich, 1976), Trapezium liratum (Reeve, 1843), and Meretrix lusoria (Röding, 1798)], found in Gangwon-do for the first time, are remnants of the Holocene warming in the Russian sector of the East Sea (Sea of Japan), thus indicating the significance of Korean waters as a transitional zone for past molluscan migrations. Keywords: Biogeography, Bivalves, East Sea (Sea of Japan), Korea, New records

Shewanella haliotisis an emerging human pathogen. Many infectious cases were linked to shellfish ingestion or aquatic exposure. Therefore, it is important to study the phylogeny and distribution ofS. haliotisin shellfish aquaculture. We investigated the distribution ofS. haliotisin cultivated shellfish farming in Taiwan in whichS. haliotiswas found in the shellfish from all sampling sites.S. haliotiswas identified in cultivated shellfish by 16S rRNA gene sequencing, such as abalone (Haliotis diversicolor), clam (Meretrix lusoria), and oyster (Crassostrea gigas). This study highlighted the contamination ofS. haliotisin cultivated shellfish and importance of further study regarding the biodiversity and pathogenesis ofS. haliotis.

Removal of phosphate (PO43−) and nitrate (NO3−) from wastewater is essential to combat the major issue of eutrophication and other harmful associated threats. Hence, this study focused on designing feasibly applied adsorbents for efficient removal of PO43− and NO3−. A novel material, Porous Floating Meretrix lusoria Shell Composite (PFSC) pellet prepared from 75 to 85% soda lime silica, 6–16% dolomite and 4–14% M. lusoria F800 shell powder was able to float on water surface, which made it remarkable to apply, collect and reuse. PFSC pellets were found to effectively remove PO43−, and were used as the carriers for immobilization of various bacteria to develop Bacterial immobilized PFSC (Bac-immo-PFSC) pellets for NO3− removal from Domestic Wastewater (DWW). Highest NO3− removal was shown by immobilized PFSC pellets in the order of B. megaterium > P. aeruginosa > Pseudomonas sp. (Isolate 2) > Bacillus sp. (Isolate 4), respectively. Interestingly, the immobilization of PFSC pellets with mixed culture of B. megaterium and P. aeruginosa can remove 100% of NO3− alongwith removal of PO43−. Maximum adsorption capacity (Qmax) of PFSC pellets for PO43− and NO3− was 362 mg/g and 3.51 mg/g, respectively, whereas, among Bac-immo-PFSC pellets, Qmax of B. megaterium-immo-PFSC and P. aeruginosa-immo-PFSC pellets were 156 mgPO43−/g, 16.9 mgNO3−/g and 169 mgPO43−/g, 13.8 mgNO3−/g, respectively. This research identified higher expression of nitrous oxide reductase gene (nosZ) in case of B. megaterium, P. aeruginosa followed by Isolate 2 and Isolate 4, respectively. Hence, the application of novel PFSC and Bac-immo-PFSC pellets can be easily applied for effective PO43− and NO3− removal and thus, can be easily collected and reused for wastewater treatment.

Shellfishes can easily accumulate metals via water and sediment and which may pose a human health risk by consumption. This study assessed the distribution of metals, including Cd, Cr, Cu, Pb, Ni, Zn, and Hg, in soft tissues of hard clam (Meretrix lusoria), surrounding water body, and sediment in the southwest coast of Taiwan. Hard clams contained the relatively higher concentration of the essential element, such as Zn, Cu, and Ni, and the metal concentration from high to low was Zn > Cu > Ni > Cd > Cr > Pb > Hg. However, the metal concentrations found in hard clam all were lower than the Sanitation Standard for Aquatic Animal of Taiwan. Results of bioaccumulation factors indicated that hard clam shows the ability of metal accumulation from water was higher than that from sediment. Moreover, the metal concentrations in hard clam were negatively correlated with body size except for Hg, which could be presented by the significant power function. Generally, hard clams from the aquaculture pond located on the southwest coast of Taiwan would not be harmful to adult consumers, except for people that consume shellfish more than 100 g. Besides strengthening the management of seafood safety and aquaculture, adjusting the eating and purchasing habits of the consumer could be a practical and feasible way for decreasing health risks. These results can assist the government in determining seafood safety and its implementation in Taiwan.

Most riverine mangroves (characterized by salinity fluctuations and tidal inundations), are seriously threatened by metallic pollution. Whether differences in salinity and tidal effects along the river continuum can affect metallic bioaccumulation and the biomagnification of species is still unknown. Bivalves are representative sessile inhabitants in mangrove ecosystems, with a high capacity to bioaccumulate metallic contaminants. The present study used two bivalves, Meretrix lusoria and Mytilopsis sallei, to monitor inter-site changes in metallic contamination and assess the associated ecological impacts along the tidal gradients of riverine mangroves. The concentrations of a total of six metals (Cr, Ni, Cu, Zn, Cd and Pb) in M. lusoria and M. sallei, collected at three different sites along Danshuei Riverine Mangrove, were investigated. The metallic concentrations of the whole soft body of the studied bivalves, and the associated surface sediment from each site, were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the inter-site effects on the bioaccumulation and biomagnification of metallic contaminants in bivalves. There are increasing concentrations of four metallic contaminants, Zn, Cr, Cd and Cu, in the seaward direction of the bivalves. The increasing mean metallic concentrations along the seaward direction may be the effect of salinity, further decreasing the rate of the elimination of these metals, thus resulting in a net increase in metallic contaminants. Our results clearly show prominent inter-site changes in the metallic burdens of bivalves in our study on riverine mangrove ecosystems associated with different levels of bioaccumulation and biomagnification of metallic contaminants. Thus, it is important to monitor multiple sites along the dynamic environment of riverine mangroves in order to gain a good understanding of the ecological impact of metallic pollution risks. The present findings provide important evidence of the use of simple indices to assess the ecological impacts of metallic pollution in riverine mangroves.

To investigate a high cholesterol diet in Alzheimer&rsquo, s disease (AD) mice, they were fed with (2% cholesterol) in five groups with a control group, AD mice group, AD mice plus Meretrix lusoria group, AD mice plus Geloina eros group, and, AD mice plus Corbicula fluminea group for three months, and treated with the fatty acid profiles of clams by gas chromatography (GC). The results showed that treatment with clams for three months reduced Fas/L and Caspase-3 in the Meretrix lusoria and Geloina eros groups, but Fas-associated death domain (FADD) and Caspase-8 were strongly reduced in the Geloina eros group. For the mitochondria-dependent apoptotic pathway, the reduction of apoptosis proteins were observed in the hearts of clams-treated AD mice. BAK and Caspase-9 was reduced in the Meretrix lusoria group, but Caspase-3 and Cytochrome-c were reduced in Geloina eros group. Enhancement of survival proteins p-AKT, p-IGF1R, p-PI3K, Bcl-XL, Bcl2, and the longevity SIRT1 signaling proteins, p-AMPK-&alpha, SIRT1, PGC1-&alpha, p-FOXO3 were observed in clams-treated mice and even more strongly enhanced in the Meretrix lusoria, Geloina eros and Corbicula fluminea groups. This study observed that the ingestion of clams caused a reduction of apoptosis proteins and enhancement of survival and SIRT1 signaling proteins in the hearts.

This study investigated spectroscopic characteristics of shell crystals of eight marine bivalve species using X-ray diffraction (XRD) analysis; moreover, the Family level relatedness of shellfish was investigated. In XRD analysis, the shells of Ruditapes philippinarum , Meretrix lusoria , Anadara granosa , and Fulvia mutica were found to have orthorhombic aragonite CaCO 3 crystals, while shells of Patinopecten yessoensis and Crassostrea gigas had trigonal-rhombohedral calcite crystals. The shells of Mytilus coruscus and Atrina pectinata were determined to have a mixture of aragonite and calcite crystals. XRD information revealed the Family level-specific characteristics of shellfish; the results agreed with the current taxonomic system. In conclusion, spectroscopic characteristics of shell crystals indicated Family-level characteristics of shellfish and suggested a more intense species-level investigation; this technology may be useful in identifying shellfish species using small quantities of shells.Key words: X-ray diffraction (XRD), CaCO

The seven selected primers BION-13, BION-29, BION-61, BION-64, BION-68, BION-72 and BION-80 generated the total number of loci, average number of loci per lane and specific loci in Meretrix lusoria (ML), Saxidomus purpuratus (SP) and Cyclina sinensis (CS) species. Here, the complexity of the banding patterns varied dramatically between the primers from the three venerid clam species. The higher fragment sizes (> 1,000 bp) are much more observed in the SP species. The primer BION-68 generated 21 unique loci to each species, which were ascertaining each species, approximately 150 bp, 300 bp and 450 bp, in the ML species. Remarkably, the primer BION-80 detected 7 shared loci by the three clam species, major and/or minor fragments of sizes 500 bp, which were matching in all samples. As regards average bandsharing value (BS) results, individuals from CS clam species (0.754) exhibited higher bandsharing values than did individuals from SP clam species (0.607) (P < 0.05). In this study, the dendrogram obtained by the seven oligonucleotides primers indicates three genetic clusters: cluster 1 (LUSORIA01-LUSORIA07), cluster 2 (PURPURATUS08-PURPURATUS14), cluster 3 (SINENSIS15- SINENSIS21). Among the twenty one venerid clams, the shortest genetic distance that displayed significant molecular differences was between individuals 18 and 20 from the CS species (genetic distance = 0.071), while the longest genetic distance among the twenty-one individuals that displayed significant molecular differences was between individuals LUSORIA no. 02 and PURPURATUS no. 09 (genetic distance = 0.778). Relatively, individuals of SP venerid species were appropriately closely related to that of CS species, as shown in the hierarchical dendrogram of genetic distances. Eventually, PCR fragments exposed in the present study may be worthwhile as a DNA marker the three venerid clam species to discriminate.

The twenty-one individuals of Meretrix lusoria were secured from Gunsan, Shinan and Yeonggwang on the coast of the Yellow Sea and the southern sea in the Korean Peninsula, respectively. Amplification of a single COI fragment (720 bp) was imagined, and no apparent size differences were observed in amplified fragments between Meretrix lusoria and M. petechialis individuals. The size of the DNA fragments also varied excitedly, from 200 to 1,600 bp. The oligonucleotides primer BION-08 produced the least loci (a total of 17), with an average of 2.43 in the Gunsan population, in comparison to the other primers used. Remarkably, the primer BION-13 detected 42 shared loci by the three populations, major and/or minor fragments of sizes 200 bp and 400 bp, respectively, which were identical in all samples. The dendrogram gained by the seven oligonucleotides primers highlight three genetic clusters: cluster 1 (GUNSAN 01 ~ GUNSAN 07), cluster 2 (SHINAN 08 ~ SHINAN 14) and cluster 3 (YEONGGWANG 15 ~ YEONGGWANG 21). The longest genetic distance among the twenty-one Meretrix lusoria individuals that displayed significant molecular differences was between individuals GUNSAN no. 01 and SHINAN no. 14 (genetic distance = 0.574). Comparatively, individuals of SHINAN population were fairly closely related to that of YEONGGWANG population. In this study, PCR analysis has discovered significant genetic distances between two white clam population pairs (P

Allozyme analysis was conducted to find out genetic diversity and structure of important fishery resources Meretrix spp. (M. lusoria, M. petechialis and Meretrix sp.) in Japan, South Korea, China and Taiwan. Samples were collected from 26 Meretrix spp. populations from Japan (20 localities), Korea (2), China (1) and Taiwan (3) between 2004 and 2008. Twelve loci from 10 enzymes were examined, and heterozygosity (He, Ho), allelic richness (A), inbreeding coefficient (Fis), pairwise Fst and Nei’s genetic distance (D) were calculated. The Taiwanese Meretrix spp. from Tanshui and aquacultured samples were consists of native species from Taiwan, because it was genetically distinct from Japanese M. lusoria. Japanese M. lusoria showed small A, low He, detective bottleneck, and these low genetic diversity was caused by drastic population decline throughout Japan after 1960’s. As a result, the degree of genetic differentiation among Japanese local M. lusoria was low. However, Mutsu, Aomori Pref, population was genetically distanced from other Japanese populations based on pairwise Fst and genetic distance. Furthermore, in the Sea of Japan M. lusoria populations, latitudinal clines were observed in the allele frequency and in He. One way gene flow between neighboring localities may explain these latitudinal clines. On the other hand, in the Pacific M. lusoria populations, the locations of samples were geographically distant from each other; however, the degree of genetic differentiation was small. The large scale of seedling release might have influenced on genetic structure of Pacific M .lusoria populations through hybridization and translocation between local individuals and introduced individuals., 論文

Samples of three hard clam Meretrix spp. (M. lusoria, M. petechialis, and Taiwanese Meretrix) were collected from 12 localities in Japan, China, Korea, and Taiwan between 2004 and 2013. PCR-RFLP analysis and nucleotide sequence analysis for the mtDNA COI region was performed on these samples. HincII and AseI restriction assay discriminated M. lusoria, M. petechialis, and Taiwanese Meretrix, corresponding to the relatively large nucleotide substitution (6.35–8.20 %). In Taiwan, M. lusoria was introduced from Japan in the 1920s; however, our results suggest that Taiwanese Meretrix is genetically differentiated from M. lusoria. As well, the exotic Taiwanese Meretrix was found from Nishinagisa on the north coast of Tokyo Bay, demonstrating the Taiwanese Meretrix now occurs with M. lusoria in its native habitat. Meretrix seedlings (Kumamoto origin) from a Taiwanese aquaculture facility has been released into Nishinagisa since 2008 suggesting the Taiwanese Meretrix is inadvertently mixed with the M. lusoria produced in the aquaculture facility. In contrast, all samples from Kisarazu, on the east coast of Tokyo Bay, were identified as M. lusoria despite there being mass releases of M. lusoria (Kumamoto origin) cultured in Taiwan since 2007. Quality control procedures are needed for future Meretrix spp. releases to prevent further spread of the Taiwanese Meretrix., 論文

The increasing volume and complexity of waste associated with the modern economy poses a serious risk to ecosystems and human health. However, the remanufacturing and recycling of waste into usable products can lead to substantial resource savings. In the present study, clam shell waste was first transformed into pure and well-crystallized single-phase white light-emitting phosphor Ca9Gd(PO4)7:Eu2+,Mn2+ materials. The phosphor Ca9Gd(PO4)7:Eu2+,Mn2+ materials were synthesized by the solid-state reaction method and the carbothermic reduction process, and then characterized and analyzed by means of X-ray diffraction (XRD) and photoluminescence (PL) measurements. The structural and luminescent properties of the phosphors were investigated as well. The PL and quantum efficiency measurements showed that the luminescence properties of clam shell-based phosphors were comparable to that of the chemically derived phosphors. Moreover, white light-emitting diodes were fabricated through the integration of 380 nm chips and single-phase white light-emitting phosphors (Ca0.979Eu0.006Mn0.015)9Gd(PO4)7 into a single package of a white light emitting diode (WLED) emitting a neutral white light of 5298 K with color coordinates of (0.337, 0.344).

Most marine mollusks are osmoconformers, in that, their body fluid osmolality changes in the direction of the change in environmental salinity. Marine mollusks exhibit a number of osmoregulatory mechanisms to cope with either hypo- or hyperosmotic stress. The effects of changes in salinity on the osmoregulatory mechanisms of the hard clam (Meretrix lusoria, an economically important species of marine bivalve for Taiwan) have not been determined. In this study, we examined the effect of exposure to hypo (10‰)- and hyper (35‰)-osmotic salinity on hard clams raised at their natural salinity (20‰). The osmolality, [Na(+)], and [Cl(-)] of the hard clam hemolymph were changed in the same direction as the surrounding salinity. Further, the contents of total free amino acids including taurine in the gills and mantles were significantly upregulated in hard clam with increasing salinity. The gill Na(+), K(+)-ATPase (NKA) activity, the important enzyme regulating cellular inorganic ions, was not affected by the changed salinity. Mantle NKA activity, however, was stimulated in the 35‰ SW treatment. The taurine transporter (TAUT) is related to the regulation of intracellular contents of taurine, the dominant osmolyte. Herein, a TAUT gene of hard clam was cloned and a TAUT antibody was derived for the immunoblotting. The TAUT mRNA expression of the mantle in hard clam was significantly stimulated in 35‰ SW, but protein expression was not modulated by the changed salinity. In gills of the hard clam with 10‰ SW, both TAUT mRNA and protein expressions were significantly stimulated, and it may reflect a feedback regulation from the decreased gills taurine content under long-term hypoosmotic acclimation. These findings suggest that TAUT expression is regulated differently in gills and mantles following exposure to alterations in environmental salinity. Taken together, this study used the physiological, biochemical and molecular approaches to simultaneously explore the osmoregulation in tissues of hard clam and may further help to understand the osmoregulation in bivalves.

The importance of biological resources has been gradually increasing, and mollusks have been utilized as main fishery resources in terrestrial ecosystems. But little is known about genomic and transcriptional analysis in mollusks. This is the first report on the transcriptomic profile of Meretrix lusoria. In this study, we constructed cDNA library and determined 542 of distinct EST sequences composed of 284 singletons and 95 contigs. At first, we identified 180 of EST sequences that have significant hits on protein sequences of the exclusive Mollusks database through BLASTX program and 343 of EST sequences that have significant hits on NCBI NR database. We also found that 211 of putative sequences through local BLAST (blastx, E

Meretrix lusoria supports an important shellfish fishery distributed around Japan and the southern coast of Korea. The species is considered to be either local extinct or endangered in Japan and in response to a decrease in availability in Japan, M. petechialis, a closely related species, has recently been imported from China and the Korean Peninsula. M. petechialis is currently defined as an “alien species” in Japan, has been released into habitats where the local species M. lusoria occurs. We conducted a survey and detected natural hybrids between M. lusoria and M. petechialis. Nineteen Meretrix spp. population samples were collected in Japan, China, and Korea from 2004 to 2006 (15 samples from Japan, two from China, and two from South Korea). Polymerase chain reaction-restriction fragment length polymorphisms in the cytochrome c oxidase subunit I region after HincII digestion and amplification of the nuclear gene ANT enabled identification of the two species. The exotic M. petechialis was found in Yoshinogawa and Kanonji, where periodically, large numbers of M. petechialis seedlings have been released. Combined results of RFLP and ANT individual genotypes suggest the existence of at least one hybrid individual and two putative hybrids between the Japanese local species M. lusoria and the continental alien species M. petechialis found in Chichibugahama and Kanonji. This is the first record demonstrating the existence of the alien species M. petechialis and of hybrids co-occurring with local M. lusoria in a natural habitat. Our results show that the alien species M. petechialis is currently relatively rare in Japan. If however, M. petechialis populations expand in the wild, they could replace the local M. lusoria and cause genetic disturbance via hybridization, as observed at one site (Kanonji, Kagawa Pref.). To conserve the endangered local M. lusoria resource, immediate controls of the release of M. petechialis will be necessary to prevent this species spreading and hybridizing with the native M. lusoria population.

Hard clams of the genus Meretrix are known to excrete a long, thick cord of mucous from the base of their siphons, but few studies have examined the clams' use of this mucous cord as a means of passive locomotion, which may result as the cord is dragged about by water currents. In the present study of Meretrix lusoria, an inhabitant of intertidal sand flats, clam migration via the mucous cord was quantified over the course of a year in the intertidal zone of the Shirakawa River estuary in Kumamoto, Japan. After tidal emersion, many M. lusoria were found among cobbles flanking a roadway across the tidal flat, evidently having been stranded there while being dragged. Stranded clams were most abundant during spring tides from March to June. Most of them were of 25–40 mm in shell length (SL) whereas most clams in the nearby sandflat were under 15 mm in SL. Furthermore, the clams stranded among the cobbles were slightly lighter than those of the same SL found buried in the sand flat. In a laboratory study using clams of 20–60 mm SL, those of 25–30 mm SL secreted mucous actively under the influence of a strong flow of seawater. In a filed experiment, out-migration occurred more frequently in lighter clams than in heavier ones. Passive migration by means of the mucous cord might be an adaptive behavior of M. lusoria, providing a mean of escape from the poor food habitats.

Here, we investigate the roles of copepods and bivalve mollusks in the transmission of white spot syndrome virus (WSSV), which is the causative pathogen of an acute, contagious disease that causes severe mortalities in cultured shrimp. Copepods are common components in seawater ponds and are often eaten as live food by shrimp post-larvae. WSSV has been detected in these animals, but it is unknown whether this was due to contamination or infection. Meanwhile, the bivalve mollusk Meretrix lusoria is often used as live food for brooders, and in Taiwan, this hard clam is sometimes co-cultured with shrimp in farming ponds. However, mollusks' ability to accumulate, or allow the replication of, shrimp viruses has not previously been studied. In this study, WSSV, the copepod Apocyclops royi and bivalve mollusk M. lusoria were experimentally challenged with WSSV and then assayed for both the presence of the virus and for viral gene expression. Results showed that the WSSV genome could be detected and that the viral loads were increased in a time-dependent manner after challenge both in A. royi and M. lusoria. Reverse transcriptase PCR monitoring of WSSV gene expression showed that WSSV could replicate in A. royi but not in M. lusoria, which suggested that WSSV, while could infect A. royi, was only accumulated in M. lusoria. A bioassay further showed that the WSSV accumulated in M. lusoria could be transmitted to Litopenaeus vannamei and cause severe infection.

The karyotypes of Meretrix lusoria and M. petechialis in the family Veneridae in Korea were studied in order to analyse their genetic relationships. The 2 species showed a diploid chromosome number of 2n=38, with 5 metacentric, 10 submetacentric, 2 subtelocentric, and 2 telocentric chromosome pairs for Meretrix lusoria, and 5 metacentric, 9 submetacentric, 3 subtelocentric, and 2 telocentric for M. petechialis. The karyotypes of these 2 species are clearly different in the same genus.

Morphological and genetic traits of Meretrix lusoria and M. petechialis were compared among individuals from Japan and Korea. Multivariate analysis of shell morphology revealed that M. lusoria from all localities of Japan (Aomori to Kyushu) and from the southern and southwestern coasts of Korea (Sacheon Bay and Gangjin Bay) have some common characters, namely more linear shape in posterior-dorsal margin, smaller width of socket and larger shell breadth rather than M. petechialis from the western coasts of Korea (Baeksu and Saemangeum). Among M. lusoria, individuals from the Japan/East Sea coasts (Yuya Bay, Aso Sea and Mutsu Bay) have more linear shape in posterior-dorsal margin than those from other localities. The distribution border between M. lusoria and M. petechialis is located around the southwestern coasts of Korea (from Gangjin Bay to Baeksu). Analyses of mitochondrial COI and nucleus ITS also revealed that individuals from Japan and the southern coasts of Korea (Sacheon Bay) were classified as M. lusoria, and those from the western coasts of Korea (Baeksu and Saemangeum) as M. petechialis. However, all individuals from Gangjin Bay were classified as M. petechialis based on the analysis of mitochondrial COI, although most individuals were classified as M. lusoria by the analysis of nucleus ITS. These results suggest that hybridization between M. lusoria and M. petechialis occurs around Gangjin Bay. Further, we established a method to identify M. lusoria and M. petechialis from shell morphology. The modified discriminant score using the 5 selected characters, i.e. shell length (L), shell breadth (B), width of socket (SW), length of posterior-dorsal margin (LPM) and height of posterior-dorsal margin (HPM), is D = 110.26−61.61(log B/log L) + 10.90(log SW/log L) − 81.72(log LPM/log L) + 27.27(log HPM/log L). Using this discriminant score, we can identify M. petechialis and M. lusoria with 98.89% correct percentage.

SUMMARY Corbicula japonica is a typical brackish water bivalve species belonging to the order Veneroida, and it is the most important inland fishery resource in Japan. Corbicula japonica has been suggested to assimilate organic matter from terrestrial plants, unlike Ruditapes philippinarum and Mactra veneriformis, which selectively assimilate organic matter of marine origin. This led us to hypothesize that C. japonica, despite being a suspension feeder, could assimilate cellulosic materials derived from terrestrial plants. In the present study, we measured cellulase and hemicellulase activities in the crystalline styles of C. japonica and other commercially important Veneroida bivalve species in Japan: Ruditapes philippinarum, Meretrix lamarckii and Meretrix lusoria. Corbicula japonica demonstrated notably higher cellulase, xylanase and β-mannanase activities than the other marine bivalves, suggesting that this species possesses a far greater biochemical capacity to break down the structural polysaccharides of plant cell walls than the other species. In contrast, the β-1,3-glucanase and pectinase activities of C. japonica were similar to or even lower than those of the others. This is possibly due to the presence of these polysaccharides in the cell walls of diatoms, a principal food of most marine bivalves. Although direct evidence is lacking, the high cellulase, xylanase and β-mannanase activities of C. japonica may result from adaptation to an upstream estuarine environment where phytoplankton and diatoms are scarce, but plant-derived substances are abundant.

We compared allozymes at 12 loci in 12 populations of six species of Meretrix: M. lusoria (Japan, Korea, and Taiwan), M. petechialis (China and Korea), M. ovum (Thailand and Mozambique), M. lyrata (China), M. lamarckii (Japan), and Meretrix sp. A (Okinawa, Japan). Our allozyme results were generally consistent with the major groupings currently recognized within the genus based on morphological characters. However, we found two cryptic or undescribed species: Meretrix sp. A from Okinawa and M. cf. lusoria from Taiwan. The shell characters of Meretrix sp. A were similar to those of M. lamarckii, but the species was genetically distinct (Nei's genetic distance D > 0.845) from all other species examined. The Taiwanese Meretrix population was morphologically indistinguishable from Japanese M. lusoria, although the genetic distance between the Taiwanese and Japanese populations showed a high degree of genetic differentiation (D > 0.386). Meretrix lusoria seedlings were introduced into Taiwan from Japa...

Predator–prey interaction in aquatic ecosystem is one of the simplest drivers affecting the species population dynamics. Predation controls are recognized as important aspects of ecosystem husbandry and management. In this paper we investigated how predation control cause an increase in host growth in the abundance of hard clam (Meretrix lusoria) populations subject to mercury (Hg)-stressed birnavirus. Here we linked predator–prey relationships with a bioenergetic matrix population model (MPM) associated with a susceptible–infectious–mortality (SIM) model based on a host–pathogen–predator framework to quantify the predator effects on population dynamics of disease in hard clam populations. Our results indicated that relative high predation rates could promote the hard clam abundances in relation to predators that selectively captured the infected hard clam, by which the disease transmission was suppressed. The results also demonstrated that predator-induced modifications in host behavior could have potential negative or positive effects on host growth depending on relative species density and resource dynamics. The most immediate implication of this study for the management of aquatic ecosystem is that, beyond the potential for causing a growth in abundance, predation might provoke greater predictability in aquatic ecosystem species populations and thereby increase the safety of ecosystem production from stochastic environmental events.

The development and larval morphology of four venerid calms, Ruditapes philippinarum, Mactra veneriformis, Cyclina sinensis, and Meretrix lusoria, which cohabit the intertidal zone in western coastal Korea, were compared using laboratory culture techniques. At 87 μm, the fertilized eggs of C. sinensis and M. lusoria were the largest and at 53 μm, those of M. veneriformis were the smallest. D-shaped larvae of M. lusoriu were the largest and those of M. veneriformis were the smallest measuring at 135 μm and 89 μm, respectively. D-shaped larvae of R. philippinarum and M. lusoria had symmetrical shoulder angles and an elliptical ventral form, in contrast to the asymmetrical shoulder angles and round ventral forms of M. veneriformis and C. sinensis. In general, pediveliger larvae of all species in the study were yellow, but those of M. veneriforks and C sinenis were a more pronounced yellow. In between the early D-shaped and pediveliger stage, 7 and 17 d elapsed for M. lusonia and C. sinensis larvae, respectively. In the early larval stages for all species, the sheU length was longer than the height. However, shell length and height later became approximately the same size in all species except R. philippinarum, which exhibited a flat shape. These results indicate that for these four venerid clams, the different characteristics in larval growth and external morphology provide the evidence necessary for larval identification of natural seed production despite the fact that they spawn concurrently in the intertidal zone.

The purpose of this study was to assess the effects of mercury (Hg) on birnavirus infection in the farmed hard clam ( Meretrix lusoria ) populations. A stage-structured matrix population model was linked with a nonlinear epidemiological dynamics of host–pathogen model to quantify the effects of increased Hg-stressed birnavirus on population dynamics of disease in hard clam populations. Bioenergetics was incorporated into population stage-structured model to enhance life cycle toxicity assessment on constraining reproduction and growth in life stages of hard clams. We delineated three qualitatively distinct scenarios of virus only, Hg + virus, and virus + Hg. Within a range of disease transmissibility drawn from analysis of Hg-stressed birnavirus in hard clams, different transmissibility led to simulated outbreaks characterized by basic reproductive number ( R 0 ) depicting the allowance population numbers to contain disease spread for all three scenarios. This study suggested that recognizing which of the scenarios best describing a situation in the field could aid in planning disease management and in choosing the most efficient and feasible strategy. The present simple model captured the essential dynamics and its flexible enough to integrate effects occurring at varying temporal scales based on biologically plausible and empirically grounded dynamical models. We were confident that the model could be easily adapted for other aquaculture species and encourage researchers to use the model to diagnose the population-level risk of toxic chemical-stressed pathogen on these species.

The purpose of this study is to develop a mechanistic-based population dynamics of disease model to predict the effect of heavy-metal stresses on the susceptibility of the aquaculture species to pollution-associated infectious diseases. We link an ecologically based nonlinear epidemiological dynamics of host–parasite interactions with a deterministic susceptibility-infectious-mortality (SIM) model to evaluate the host susceptibility to the waterborne metal stressors. We test the proposed pollution-associated population dynamics of disease model against published data regarding the effect of metal cations (Cd 2+ , Cu 2+ , and Hg 2+ ) on the susceptibility of hard clam ( Meretrix lusoria ) to birnavirus. We estimate stressor-specific transmission rate and basic reproductive number ( R 0 ), defined as the average number of secondary cases generated by one primary infected case, by fitting SIM model to published cumulative mortality data. The median pollution-associated R 0 estimates range from 0.99 to 1.03. Here we show that the interplay of environmental chemical stressors and disease transmission explains the host–pathogen interactions presenting in the immunomodulating chemicals contaminated aquacultural systems, suggesting that predicting schemes will require the consideration of both environmental stressor variability and host size in aquaculture species populations. We suggest that in the future potential management actions the pathogen manipulation is better to be integrated to improve the on-line environmental stressors monitoring in aquacultural systems.

Three amylases were purified to electrophoretic homogeneity from viscera of hard clam Meretrix lusoria by ammonium sulfate fractionation, Sepharose 6B, DEAE-Sephadex A-50, Sephadex G-200 and PBE 94 chromatographies. The purified amylases had molecular masses of 49.6, 58.7 and 100 kDa and were designated AI-1, AI-2 and AII, respectively. Both AI-1 and AI-2 could digest amylose into glucose and maltose, while AII could digest amylose and pullulan into glucose. The optimal pH and temperatures for AI-1, AI-2 and AII were 7.0, 7.5 and 7.5, and 40, 50 and 50°C, respectively. According to the substrate specificity, the purified AI-1 and AI-2 were considered to be multifunctional exo- and endo-types of α-amylase-like enzymes, while AII was exo-type γ-amylase-like enzyme. They were Ca2+-independent enzymes.

Species composition and distribution patterns of shellfish were investigated in Eoeun and Geojeon tidal flat located in the Saemangeum area on the west coast of Korea from May to October 2000. Nineteen species of shellfish were collected in Geojeon tidal flat. The samples in number of individuals included Umbonium thomasi and Mactra veneriformis In Eoeun tidal flat, ten species of shellfish were collected and the dominant species in number of individuals were Potamocorbula amurensis and U. thomasi These results were compared with previous studies conducted before the beginning of reclamation in Saemangeum. Compared with the results from 1988, a change In species composition was observed. Laternula flexuosa and Nuttallia olivacea appeared, while Mactra chinensis and Coelomactra antiquata disappeared in the deposition area in Geojeon tidal flat. In the erosion area of Eoeun tidal flat, M. veneriformis and Meretrix lusoria appeared, while Cyclina sinensis disappeared. Based on a cluster analysis, the shellfish community in Eoeun tidal flat was classified into three station groups based on sediment types. Geojeon tidal flat was also classified into three station groups. The distribution of shellfish in the Saemangeum area was closely related to the sediment types.

Recent microbiological data have revealed that Gram-negative bacteria are able to protect themselves against the lytic action of host lysozymes by secreting proteinaceous inhibitors. Four distinct classes of such inhibitors have been discovered that specifically act against c-type, g-type and i-type lysozymes. Here, the 1.24 Å resolution crystal structure of the periplasmic i-type lysozyme inhibitor from Aeromonas hydrophila (PliI-Ah) in complex with the i-type lysozyme from Meretrix lusoria is reported. The structure is the first to explain the inhibitory mechanism of the PliI family at the atomic level. A distinct `ridge' formed by three exposed PliI loops inserts into the substrate-binding groove of the lysozyme, resulting in a complementary `key-lock' interface. The interface is principally stabilized by the interactions made by the PliI-Ah residues Ser104 and Tyr107 belonging to the conserved SGxY motif, as well as by the other conserved residues Ser46 and Asp76. The functional importance of these residues is confirmed by inhibition assays with the corresponding point mutants of PliI-Ah. The accumulated structural data on lysozyme-inhibitor complexes from several classes indicate that in all cases an extensive interface of either a single or a double `key-lock' type is formed, resulting in highly efficient inhibition. These data provide a basis for the rational development of a new class of antibacterial drugs. journal: Acta Crystallographica Section D: Biological Crystallography content_type: research papers peer_reviewed: Yes review_process: Single blind received: 2 July 2014 accepted: 26 November 2014 published_online: 23 January 2015 supplementary_materials: This article has supporting information copyright: © 2015 International Union of Crystallography ispartof: Acta Crystallographica D vol:71 issue:Pt 2 pages:344-351 ispartof: location:United States status: published

The tetramethylarsonium ion has been found in the gill of the clam Meretrix lusoria. We attempted to confirm the conversion of arsenobetaine to the tetramethylarsonium ion in a culture with marine microorganisms occurring in the gill of the clam Meretrix lusoria. Arsenobetaine was aerobically incubated with microorganisms. A garlic-like odor was faintly detected after 5 to 8 days incubation. The mass spectrum of the odorous substance was essentially identical with that of synthetic trimethylarsine. Trimethylarsine oxide (TMAO) was also detected in the culture medium after 3 weeks incubation. Arsenobetaine was biotransformed to TMAO during the incubation in the culture growth by the marine microorganisms. Tetramethylarsonium ion was not detected in the culture medium even after 72 days incubation.

The uptake and transfer of 2,2′,4,4′-tetrachlorobiphenyl (an isomer of polychlorinated biphenyls, PCBs) in the culture of two species of phytoplankton, Nannochloropsis oculata and Isochrysis galbana, to brine shrimp (Artemia sp.) nauplii and hard shell clam (Meretrix lusoria) were investigated in a short-term laboratory ecosystem. Three PCB concentrations, 0 ppb, 50 ppb and 500 ppb, were prepared in the algal culture for examing the levels of PCB bioaccumulation and growth effects on these biota. Artemia and hard shell clam each when exposed to 500 ppb contaminated Nannochloropsis and Isochrysis for 4 d could significantly bioaccumulate PCB concentrations up to 318.81 ppm and 22.55 ppm (dry basis), respectively. This may account for the high PCB residues that bioaccumulated in contaminated Nannochloropsis (257.52 ppm) and Isochrysis (64.22 ppm) through the aquatic food chain. Biomass of PCB treated algae were apparently depressed (p < 0.05) relative to that of the control group (0 ppb). Growth conditions (length and larva/mL) of Artemia when fed with Nannochloropsis under PCB environments also showed stronger inhibition effects compared to that of the control group (p < 0.05).

The hard clams (Meretrix lusoria) that are cultured in Taiwan have suffered high mortalities each spring and/or summer since 1969. Environmental factors, pollution and infectious diseases have been implicated, but no single factor has been shown to lead directly to large-scale death of the cultured hard clam. In the present study, attempts were made to examine the effects of heavy metals on the susceptibility of the hard clam to birnavirus infection. First we determined the stability of the clam birnavirus in sea, brackish, fresh waters at 4, 15 and 26°C and in solutions containing different concentrations of Zn2+, Cd2+, Cu2+, and Hg2+. For each heavy metal cation, two concentrations which had no influence on clam birnavirus infectivity were selected and used to treat the hard clams before and after virus infection. In experiment I, clams were immersed in 105.0 TCID50 /ml virus solution for 24 h and subsequently exposed to one of the heavy metals. Cumulative mortalities of clams were 20∼52% in most experimental groups although mortalities reached 91% in infected clams exposed to high concentrations of copper. In experiment II, groups of 60 clams were exposed to one of the heavy metals for 7 days and then infected with the virus, while controls were only expose to heavy metals. Mortalities of clams in the experimental groups reached 65∼90% within 28 days, while only 10% mortalities were observed in the groups that were exposed to either heavy metals or virus infection alone.

To determine the structure and functional relationships of invertebrate lysozymes, we isolated a new invertebrate (i)-type lysozyme from the common orient clam (Meretrix lusoria) and determined the complete amino acid sequence of two isozymes that differed by one amino acid. The determined sequence showed 65% similarity to a lysozyme from Venerupis philippinarum (Tapes japonica), and it was therefore classified as an i-type lysozyme. The lytic activities of this lysozyme were similar to those of previously reported bivalve i-type lysozymes, but unlike the V. philippinarum lysozyme, it did not exhibit an increase in activity in high ionic strength. Our data suggest that this lysozyme does not have a dimeric structure, due to the replacement of Lys108 which contributes to dimer formation in the V. philippinarum lysozyme. GlcNAc oligomer activities suggested an absence of transglycosylation activity and a higher number of subsites on this enzyme compared with hen egg lysozyme.

This paper evaluates the relationships between copper species in sediments and accumulation by the purple clam (Hiatula diphos) and venus clam (Gomphina aeguilatera) collected from the field and culture (aquaculture) ponds in the polluted coastal area of Lukang, Taiwan. Sediment was sampled along with the molluscs, including oysters (Crassostrea gigas), purple clams (Hiatula diphos), rock-shells (Thais clavigera), venus clams (Gomphina aeguilatera), and hard clams (Meretrix lusoria), from two unique environments of Lukang during the period from August 1993 to July 1994. The data indicate that the total copper concentrations in sediments from culture ponds (185 microg g(-1)) was higher than those of the field (44.0 microg g(-1)). Copper species in sediments were analyzed by a sequential leaching technique. Results show that concentrations of various copper species in the sediments are in the range of 1.14 +/- 0.59 to 13.2 +/- 22.4 microg g(-1) and 0.36 +/- 0.24 to 133 +/- 36.7 microg g(-1) for the two environments, respectively. Also the exchangeable copper in sediment from culture ponds was 15 times higher than that from the field. In addition, the sum of exchangeable and copper carbonates had the highest percentages of copper in both the pond sediment (86.6 %) and the field sediment (50.7 %). Maximum copper concentrations (309 +/- 35.1 microg g(-1)) in oysters were much higher than those in the other benthic organisms by about 4-127 times. Similarly, the data also showed that copper concentrations in Thais clavigera were 12-32 times higher than those in other benthic organisms. Copper concentrations in various benthic organisms differed significantly (p0.05) from that in Thais clavigera. This capacity makes Thais clavigera a potential candidate for monitoring copper in marine sediments. In terms of copper species, the best correlation was generally obtained between copper carbonates in sediments and copper concentrations in Hiatula diphos (r = 0.886*). A strong multiple regression correlation (p0.05, r2 = 0.7894) also indicates that the copper carbonates may dominate as the available form of copper to Hiatula diphos from various environments in the Lukang coastal area under natural physicochemical conditions.

Clam virus (CV HB-1) isolated from hard clam Meretrix lusoria , typed as infectious pancreatic necrosis virus (IPNV) Ab serotype, was employed for the present study. The structural polypeptides of purified virus generated by serial undiluted and diluted passaging were analyzed using sodiumdodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The results indicated that in VP2, the virus particles of serial undiluted passaging had viral polypeptides smaller than those of serial diluted passaging. Furthermore, a polypeptide with a molecular mass of 105 kDa was found in the serial undiluted virus preparation. Further analysis by monoclonal antibodies showed that VP105 might be a polyprotein produced by genomic RNA segment A. To investigate the sequential changes of viral polypeptides of the virus preparation at high multiplicity infection, the viral polypeptides at each undiluted passage were analyzed by SDS-PAGE followed by immunoblotting. The results indicated that VP105 was present by undiluted passage 7, while the smaller VP2 was present by undiluted passage 10. The amount of smaller VP2 and VP105 increased as the number of passages increased.