Hard Clam Meretrix Lusoria Research Articles

Oral Zinc-Rich Oyster Supplementation Corrects Anemia in Rats

This study investigates the impact of various zinc supplementation methods on anemia in rats induced by phenylhydrazine (PHZ) and in 5/6-nephrectomized anemic rats. We compare oral zinc sulfate (ZnSO4) supplementation, oyster Crassostrea gigas supplementation, and hard clam Meretrix lusoria supplementation on red blood cell (RBC) levels. Oral zinc-rich oyster supplementation (2.70 mg Zn (30 g oyster)/day/rat) effectively corrects anemia in both experimental groups. Rats orally fed oysters for four days exhibit similar effectiveness as those receiving a single ZnSO4 injection (0.95 mg Zn (4.18 mg ZnSO4⋅7H2O)/rat). In contrast, oral ZnSO4 supplementation (2.70 mg Zn (11.88 mg ZnSO4⋅7H2O)/day/rat) does not significantly increase RBC levels, suggesting better zinc absorption from oysters. A placebo group of anemic rats supplemented with hard clams, similar in composition to oysters but much lower in zinc, did not change RBC counts. This supports oysters’ high zinc content as the key to correcting anemia. Oysters also contain high iron levels, offering a potential solution for iron-deficiency anemia while supporting bone marrow erythropoiesis. In summary, oral oyster supplementation emerges as an effective strategy to correct anemia in rats with added zinc and iron support for erythropoiesis.

Polystyrene as a vector of heavy metals in hard clam Meretrix lusoria under various salinities

Microplastics and heavy metals are the two main contaminants that are often found in aquatic environments and can lead to major issues for aquatic organisms. Polystyrene (PS) is a type of microplastic that is commonly found in aquatic environments. Hard clams are one of the organisms that are often used as a bioindicator of water pollution, and they can live in a certain salinity range. The objective of this study is to investigate the potential of PS particles as heavy metal vectors in M. lusoria influenced by differences in salinity. The result showed that the highest increase in concentrations of all heavy metals in hard clams was found in those placed at higher salinities. Hard clams that were placed at higher salinity required more water, allowing more PS particles to enter the clams’ bodies. Hard clams placed at salinity 30‰ always gathered significantly more PS particles (p<0.05) than hard clams placed at the other two salinities (20 and 25‰). This is also corroborated by water depletion at a salinity of 30‰, which is significantly higher (p<0.05) than the other two salinities. Our findings indicate that PS particles have the potential as vectors for heavy metal pollutants in hard clams in environments of varying salinity.

Time-course changes in the regulation of ions and amino acids in the hard clam Meretrix lusoria upon lower salinity challenge.

In this study, we examined ion and amino acid regulation in the gill and mantle of the hard clam Meretrix lusoria. We found that the osmolality and Na+ and Cl- concentrations of hard clam hemolymph were significantly reduced after transferring clams from the salinity of their natural habitat [20‰ saltwater (SW)] to a lower salinity environment (10‰ SW). Specific activities of Na+ , K+ -ATPase (NKA), which provides the driving force for the secondary ion transport associated with cell osmoregulation in gills and mantles, were unaffected during the acclimation to lower salinity. In contrast, there was a significant decline in the contents of free amino acids (FAAs) in the gills and mantles of hard clams during lower salinity acclimation. Taurine was established to be the dominant FAA, the content of which is considerably higher than that of other FAAs in the hard clam. Following acclimation to the lower salinity environment, mRNA expression of the taurine transporter (TAUT), which plays a pivotal role in regulating intracellular taurine contents, was significantly upregulated in the gill and downregulated in the mantle of hard clams at different time points. However, the relative abundance of TAUT protein in the gill and mantle was significantly increased after transfer from 20‰ SW to 10‰ SW, which may reflect feedback regulation in response to reduced taurine contents in the gill and mantle of hard clams. Collectively, the findings of this study provide important insights on the dynamic processes of ion and amino acid regulation in the peripheral tissues of bivalves.

Microplastic Contamination of Three Commonly Consumed Seafood Species from Taiwan: A Pilot Study

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’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−1 was 87.9 microplastics kg−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.

Histological Observations of the Digestive Gland of the Hard Clam Meretrix lusoria and Its Relation to Summer Mortality in Grow-Out Cultures in Tokyo Bay, Central Japan

Histological Observations of the Digestive Gland of the Hard Clam Meretrix lusoria and Its Relation to Summer Mortality in Grow-Out Cultures in Tokyo Bay, Central Japan

Recruitment and movement of the hard clam Meretrix lusoria in a tidal river of northern Kyushu, Japan

Size-frequency distributions of Meretrix lusoria, a commercially important bivalve in Japan, were compared among 6 sites in tidal flats of a small river in Kafuri Bay, northern Kyushu, Japan during 2006–2008. In Kafuri Bay, the hard clam resource is strictly managed and mean biomass of this species on the fishing ground (about 1.5 km2) exceeded 1.5 kg m−2 in 2008. Small clams ( 40 mm SL) were rare there. In contrast, in the lower site of the marine area (site L), most clams were >30 mm SL. These results indicate that small clams move from riverine to marine areas with growth (post-settlement movement). Year-round, very small clams ( 5 mm SL in a short period of time.

Distribution and movement between habitats with growth of the hard clam Meretrix lusoria in the Shirakawa–Midorikawa estuary of the Ariake Sea

The distribution and movement between habitats with growth of the hard clam Meretrix lusoria were examined by comparing the size–frequency distributions among 17 sites in the Shirakawa–Midorikawa Estuary of the Ariake Sea. This clam is a commercially important bivalve in Japan, and its annual catch is largest in the Ariake Sea. At the study sites, new recruits were abundant at river mouths, and density was strongly affected by the distance from coastal tidal rivers and streams. In contrast, adults were widely distributed on tidal flats, although density was low at many sites. At marine site Oda, the density of adults was higher than that of new recruits at all sites and higher than that of juveniles at most sites. These results indicate that this species moves from riverine sites to marine sites with growth. Moreover, the observed low density of adult clams may indicate overfishing. The active movement of M. lusoria across the fishing grounds complicates the sustainable resource management of this species. Therefore, further studies are needed for effective resource management of M. lusoria.

Purification and kinetic characteristics of strombine dehydrogenase from the foot muscle of the hard clam (Meretrix lusoria)

Strombine dehydrogenase (SDH, EC 1.5.1.22) from the foot of the hard clam Meretrix lusoria was purified over 470-fold to apparent homogeneity. It has a monomeric structure with a relative molecular mass of 46,000. Two isoenzymes were identified with isoelectric points of 6.83 and 6.88. SDH is heat labile, and has pH and temperature optima of 7.4-7.6 and 45-46°C, respectively. l-Alanine, glycine, and pyruvate are the preferred substrates. l-Serine is the third preferred amino acid. Iminodiacetate with the lowest K(i) of SDH at both pH 6.5 and 7.5 was the strongest inhibitor among succinate, acetate, iminodiacetate, oxaloacetate, and l-/d-lactate. The inhibitory activities of succinate at pH 6.5, and iminodiacetate and oxaloacetate at pH 7.5 on the SDH were higher. These inhibitors are either competitive or mixed-competitive inhibitors. Half of the enzymatic activity of SDH was inhibited by 0.2mM Fe(3+) and 0.6mM Zn(2+).

Risk-Based Probabilistic Approach to Assess the Impact of False Mussel Invasions on Farmed Hard Clams

The purpose of this article is to provide a risk-based predictive model to assess the impact of false mussel Mytilopsis sallei invasions on hard clam Meretrix lusoria farms in the southwestern region of Taiwan. The actual spread of invasive false mussel was predicted by using analytical models based on advection-diffusion and gravity models. The proportion of hard clam colonized and infestation by false mussel were used to characterize risk estimates. A mortality model was parameterized to assess hard clam mortality risk characterized by false mussel density and infestation intensity. The published data were reanalyzed to parameterize a predictive threshold model described by a cumulative Weibull distribution function that can be used to estimate the exceeding thresholds of proportion of hard clam colonized and infestation. Results indicated that the infestation thresholds were 2-17 ind clam(-1) for adult hard clams, whereas 4 ind clam(-1) for nursery hard clams. The average colonization thresholds were estimated to be 81-89% for cultivated and nursery hard clam farms, respectively. Our results indicated that false mussel density and infestation, which caused 50% hard clam mortality, were estimated to be 2,812 ind m(-2) and 31 ind clam(-1), respectively. This study further indicated that hard clam farms that are close to the coastal area have at least 50% probability for 43% mortality caused by infestation. This study highlighted that a probabilistic risk-based framework characterized by probability distributions and risk curves is an effective representation of scientific assessments for farmed hard clam in response to the nonnative false mussel invasion.

Candidates for a hypoxia-stress indicator in the hard clam, Meretrix lusoria

The Lt 50 (median lethal time) of hard clam Meretrix lusoria exposed to anoxia was 15.7, 9.7, 3.8, 2.8, and 2.5 days at 15, 20, 25, 30, and 34 °C, respectively. The concentration of alanine and succinate was 5.6 and 0.6 μmol/g in the foot, and the concentration of succinate was 1.6 μmol/ml in the body fluid for the clams following 5 days exposure to normoxia at 30 °C. However, the concentration of alanine, succinate, and propionate was 15.6, 9.7, and 1.4 μmol/g in the foot, and 0.58, 35.3, and 3.66 μmol/ml in the body fluid, respectively for the clams following 5 days anoxic exposure at 30 °C. Clams secreted 97.9 nmol/g of succinate, and 76.7 nmol/g of propionate during the anoxic exposure at 30 °C. Similarly, the concentration of alanine, succinate, and propionate was 14.2, 8.9, and 1.3 μmol/g in the foot, and 0.27, 37.9, and 6.1 μmol/ml in the body fluid for the clams following 8 days exposure to anoxia at 15 °C. Clams secreted 18.9 nmol/g of succinate and 103 nmol/g of propionate during anoxic exposure at 15 °C. Clams that were visible at the surface of the sediment (half-buried or fully exposed) showed significantly higher concentration of alanine in the foot, and concentration of succinate in the body fluid than those completely buried in the sediment. It is suggested that the concentration of alanine in the foot greater than 11 μmol/g and the concentration of succinate in the body fluid greater than 4 μmol/ml are considered indicators of hypoxia in hard clams.

Predation affects the susceptibility of hard clam Meretrix lusoria to Hg-stressed birnavirus

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.

Hard clam Meretrix lusoria to Hg-stressed birnavirus susceptibility revealed through stage-structured disease transmission dynamics

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.

Simultaneous flow cytometric assessment for cellular types and phagocytic abilities of the haemocytes of the hard clam, Meretrix lusoria

The aim of this study was to devise a simple protocol for flow cytometric analysis to separate various haemocytic populations of the hard clam Meretrix lusoria based on the mitochondrial membrane potential diversity detected by the fluorescence probe 3,3-dihexyloxacarbocyanine iodide (DiOC6). Compared with the traditional technique for separation of haemocytic populations, continuous Percoll gradient centrifugation, our novel method was more efficient and yielded a higher ratio in separating the clams' haemocytic populations. Based on fluorescence 1 (FL-1) and side scatter (SSC) analysis for haemocytes stained with various fluorescent densities of DiOC6 using flow cytometer, the data showed that there were three obvious cell regions R1, R2, and R3, identified by hyalinocytes, small granulocytes and large granulocytes, respectively. At the same time our results showed that the percentages of haemocytes in R1, R2, and R3 were 49.71 ± 0.65%, 19.35 ± 00.74%, 30.94 ± 0.69%, respectively. After classifying the haemocytic populations, phagocytic activity of the haemocytes was simultaneously analysed with phycoerythrin (PE)-labeled Vibrio vulnificus and detected by flow cytometry. Our results demonstrated that there were higher percentages of large granulocytes compared with hyalinocytes and the percentage of small granulocytes was related to the mitochondrial membrane potential and phagocytic activities.

Purification and characterization of three amylases from viscera of hard clam Meretrix lusoria

: 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.

The sequential changes of the virion polypeptides of CV HB1 virus (Birnaviridae) during serial undiluted passaging

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.

Recent innovations in cultivation of edible molluscs in Taiwan, with special reference to the small abalone Haliotis diversicolor and the hard clam Meretrix lusoria

Annual production and culture area of small abalones and hard clams have surprisingly increased in recent years. The factors contributing to this increase, aside from heavy demand and high price, include new techniques in catching the tiny clam seed (0.5 mm in size), success in mass production of seed of both species in hatcheries, better understanding of the molluscs' biology as well as their response to environmental changes, improved management of water quality to provide the optimal growth conditions, cheap and easy supply of Gracilaria for abalone feed, use of powdered formulated feed for hard clams, application of chicken manure and rice bran to enrich the water, intermediate harvest of animals of marketable size, and control of predators. However, major constraints to further development and expansion of molluse cultivation remain, including water pollution from industrial wastes, limited area with suitable water supply, strict regulations on the use of seashore land and littoral zone, and the lack of export market. Other species of molluscs, including the oyster Crassostrea gigas, the short-necked clam Comphina veneriforms, the purple clam Soletellina diphos, the cockle anadara granosa, and the small freshwater clam Corbicula, have potential for further expansion if problems of seed supply, water pollution, control of disease, and market price are properly solved.

Recent innovations in cultivation of edible molluscs in Taiwan, with special reference to the small abalone Haliotis diversicolor and the hard clam Meretrix lusoria: Chen, Hon-Cheng, 1984. Aquaculture, 39(1/4):11–27

Recent innovations in cultivation of edible molluscs in Taiwan, with special reference to the small abalone Haliotis diversicolor and the hard clam Meretrix lusoria: Chen, Hon-Cheng, 1984. Aquaculture, 39(1/4):11–27

Growth of the hard clam Meretrix lusoria in Taiwan

The growth of hard clam Meretrix lusoria in Taiwan was observed as it was grown at six different stocking rates (55, 109, 172, 244, 344 and 455 clams/m 2), from November 1979 to September 1980. It was found that the stocking rate had more effect on the increase of the total weight of the clam than on the shell length. Under the environmental condition of the study site, the optimum stocking rate was 244 clams/m 2. When the net production of the clam was lower than 1103 g/m 2, the growth of the individual clam was not affected by the stocking rate. But when the net production was higher than 1589 g/m 2, the growth of the individual clam seemed to be retarded. The average pH of the sea water in the clam culture area was between 7.9 and 8.4. The average dissolved oxygen content was between 4.2 and 11.2 mg/l. And the average water salinity was between 30‰ and 35‰. All these three factors did not seem to have direct relationship with the growth of the clams. Sea water temperature, however, showed great effects on the growth of the clams. It is shown that the growth of the hard clam was slow at a water temperature of 15–18°C, increased at 20–22°C, and accelerated at 25–32°C.